Conflict detection and logging in logical replication

From b5c89d2b85fc708367c2b52a2a611781560d6feb Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Fri, 21 Jun 2024 10:41:49 +0800
Subject: [PATCH v2 2/2] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_workers to shows
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_counts:
	Number of times inserting a row that iolates a NOT DEFERRABLE unique constraint.
update_differ_counts:
	Number of times updating a row that was previously modified by another origin.
update_missing_counts:
	Number of times that the tuple to be updated is missing.
delete_missing_counts:
	Number of times that the tuple to be deleted is missing.

The conflicts will be tracked only when track_conflict option of the
subscription is enabled. Additionally, update_differ can be detected only
when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  | 52 ++++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |  4 +-
 src/backend/catalog/system_views.sql          |  4 +
 src/backend/replication/logical/conflict.c    |  4 +
 .../utils/activity/pgstat_subscription.c      | 17 ++++
 src/backend/utils/adt/pgstatfuncs.c           | 20 ++++-
 src/include/catalog/pg_proc.dat               |  6 +-
 src/include/pgstat.h                          |  4 +
 src/include/replication/conflict.h            |  2 +
 src/test/regress/expected/rules.out           |  6 +-
 src/test/subscription/t/026_stats.pl          | 77 +++++++++++++++++--
 11 files changed, 178 insertions(+), 18 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index b2ad9b446f..0ceb71f214 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2163,6 +2163,56 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times inserting a row that violates a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times updating a row that was previously modified by another
+       source while applying changes. This conflict is counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated is not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted is not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index ce37fa6490..06bea458a6 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 30393e6d67..182836ac82 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1370,6 +1370,10 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index f24f048054..ca58b708ef 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -75,6 +77,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e8ddb749a7 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,7 +1966,7 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	8
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
@@ -1985,7 +1985,15 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -2005,11 +2013,15 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	/* sync_error_count */
 	values[2] = Int64GetDatum(subentry->sync_error_count);
 
+	/* conflict count */
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		values[3 + i] = Int64GetDatum(subentry->conflict_count[i]);
+
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[7] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[7] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 6a5476d3c4..08bc966a2f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5505,9 +5505,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_differ_count,update_missing_count,delete_missing_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 2136239710..b957e7ad36 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 0bc9db991e..40dcb1d9ad 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -33,6 +33,8 @@ typedef enum
 	CT_DELETE_MISSING,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_MISSING + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 13178e2b3d..80a6857b00 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2141,9 +2141,13 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_differ_count, update_missing_count, delete_missing_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..f81ce66540 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,47 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Update and delete data to test table on the publisher, skipping the
+	# update and delete on the subscriber as there are no data in the test
+	# table.
+	$node_publisher->safe_psql($db, qq(
+		UPDATE $table_name SET a = 2;
+		DELETE FROM $table_name;
+	));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data to test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +171,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +193,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +237,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +258,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +274,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.31.1

From 89251f12346e891f888ea4b086fb7255b926daff Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@fujitsu.com>
Date: Fri, 31 May 2024 14:20:45 +0530
Subject: [PATCH v2] Detect and log conflicts in logical replication

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will
go for confict detection. By default, conflict detection will be off for a
subscription.

When conflict detection is enabled, additional logging is triggered in the
following conflict scenarios:

insert_exists: Inserting a row that iolates a NOT DEFERRABLE unique constraint.
update_differ: updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.

For insert_exists conflict, the log can include origin and commit
timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ conflict can only be detected when track_commit_timestamp is
enabled.
---
 doc/src/sgml/catalogs.sgml                  |   9 +
 doc/src/sgml/ref/alter_subscription.sgml    |   5 +-
 doc/src/sgml/ref/create_subscription.sgml   |  55 ++++++
 src/backend/catalog/pg_subscription.c       |   1 +
 src/backend/catalog/system_views.sql        |   3 +-
 src/backend/commands/subscriptioncmds.c     |  31 +++-
 src/backend/executor/execIndexing.c         |  14 +-
 src/backend/executor/execReplication.c      | 117 +++++++++++-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 187 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  50 ++++--
 src/bin/pg_dump/pg_dump.c                   |  17 +-
 src/bin/pg_dump/pg_dump.h                   |   1 +
 src/bin/psql/describe.c                     |   6 +-
 src/bin/psql/tab-complete.c                 |  14 +-
 src/include/catalog/pg_subscription.h       |   4 +
 src/include/replication/conflict.h          |  44 +++++
 src/test/regress/expected/subscription.out  | 176 ++++++++++--------
 src/test/regress/sql/subscription.sql       |  15 ++
 src/test/subscription/t/001_rep_changes.pl  |  15 +-
 src/test/subscription/t/013_partition.pl    |  48 ++---
 src/test/subscription/t/029_on_error.pl     |   5 +-
 src/test/subscription/t/030_origin.pl       |  26 +++
 src/tools/pgindent/typedefs.list            |   1 +
 25 files changed, 695 insertions(+), 151 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index a63cc71efa..a9b6f293ea 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8034,6 +8034,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index 476f195622..5f6b83e415 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -228,8 +228,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-disable-on-error"><literal>disable_on_error</literal></link>,
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
-      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>.
+      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..ce37fa6490 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,61 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated is not found.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted is not found.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index efb29adeb3..30393e6d67 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1360,7 +1360,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index e407428dbc..e670d72708 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -70,8 +70,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -97,6 +98,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -159,6 +161,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -316,6 +320,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -603,7 +616,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -710,6 +724,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1146,7 +1162,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_STREAMING | SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1256,6 +1272,13 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..2a2d188b19 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,6 +522,11 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		If the 'slot' holds a tuple with valid tid, this tuple will
+ *		be ingored when checking conflict. This can help in scenarios
+ *		where we want to re-check for conflicts after inserting a
+ *		tuple.
  * ----------------------------------------------------------------
  */
 bool
@@ -536,11 +542,9 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	ExprContext *econtext;
 	Datum		values[INDEX_MAX_KEYS];
 	bool		isnull[INDEX_MAX_KEYS];
-	ItemPointerData invalidItemPtr;
 	bool		checkedIndex = false;
 
 	ItemPointerSetInvalid(conflictTid);
-	ItemPointerSetInvalid(&invalidItemPtr);
 
 	/*
 	 * Get information from the result relation info structure.
@@ -629,7 +633,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, &slot->tts_tid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..f01927a933 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -480,6 +481,83 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * Return false if there is no conflict and *conflictslot is set to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned
+ * in *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			goto retry;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			goto retry;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return true;
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +587,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +605,43 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes, &conflict,
+												   conflictindexes, false);
+
+		/* Re-check all the unique indexes for potential conflicts */
+		foreach_oid(uniqueidx, (conflict ? conflictindexes : NIL))
+		{
+			TupleTableSlot *conflictslot;
+
+			/*
+			 * Reports the conflict if any.
+			 *
+			 * Here, we attempt to find the conflict tuple. This operation may
+			 * seem redundant with the unique violation check of indexam, but
+			 * since we perform this only when we are detecting conflict in
+			 * logical replication and encountering potential conflicts with
+			 * any unique index constraints (which should not be frequent), so
+			 * it's ok. Moreover, upon detecting a conflict, we will report an
+			 * ERROR and restart the logical replication, so the additional
+			 * cost of finding the tuple should be acceptable in this case.
+			 */
+			if (list_member_oid(recheckIndexes, uniqueidx) &&
+				FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+			{
+				RepOriginId origin;
+				TimestampTz committs;
+				TransactionId xmin;
+
+				GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+				ReportApplyConflict(ERROR, CT_INSERT_EXISTS, rel, uniqueidx,
+									xmin, origin, committs, conflictslot);
+			}
+		}
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..f24f048054
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,187 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+			{
+				/*
+				 * Bulid the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin %u in transaction %u at %s.",
+									 index_value, get_rel_name(conflictidx), localorigin,
+									 localxmin, timestamptz_to_str(localts));
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			return errdetail("Updating a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	/* Assume the index has been locked */
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b5a80fe3e8..af73e09b01 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2461,7 +2462,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2664,6 +2668,20 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2681,13 +2699,10 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2821,13 +2836,10 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -3005,13 +3017,13 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index e324070828..c6b67c692d 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4739,6 +4739,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4811,11 +4812,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4854,6 +4861,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4900,6 +4908,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5140,6 +5150,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 865823868f..02aa4a6f32 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index f67bf0b892..0472fe2e87 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6529,7 +6529,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6597,6 +6597,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d453e224d9..219fac7e71 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..0bc9db991e
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 0f2a25cdc1..a8b0086dd9 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,10 +371,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 --fail - alter of two_phase option not supported.
@@ -383,10 +383,10 @@ ERROR:  unrecognized subscription parameter: "two_phase"
 -- but can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -396,10 +396,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -412,18 +412,42 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 3e5ba4cb8c..a77b196704 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -290,6 +290,21 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,11 +331,12 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
 
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
@@ -352,10 +353,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..c64f17211d 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,12 +343,12 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
 
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
@@ -372,21 +372,21 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
 
 # Tests for replication using root table identity and schema
 
@@ -773,12 +773,12 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
 
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
@@ -796,15 +796,15 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..496a3c6cd9 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict insert_exists detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(1\) already exists in unique index "tbl_pkey", which was modified by origin \d+ in transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -109,7 +110,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..03dabfeb72 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -26,7 +26,12 @@ my $stderr;
 # node_A
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_A->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
@@ -89,11 +94,32 @@ is( $result, qq(11
 	'Inserted successfully without leading to infinite recursion in bidirectional replication setup'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update a row that
+# was previously modified by a different source.
+###############################################################################
+
+$node_A->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_AB SET (detect_conflict = true);");
+
+$node_B->safe_psql('postgres', "UPDATE tab SET a = 10 WHERE a = 11;");
+
+$node_A->wait_for_log(
+	qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
 $node_A->safe_psql('postgres', "DELETE FROM tab;");
 
 $node_A->wait_for_catchup($subname_BA);
 $node_B->wait_for_catchup($subname_AB);
 
+# The remaining tests no longer test conflict detection.
+$node_A->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_AB SET (detect_conflict = false);");
+
+$node_A->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_A->restart;
+
 ###############################################################################
 # Check that remote data of node_B (that originated from node_C) is not
 # published to node_A.
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 61ad417cde..f42efe12b7 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -465,6 +465,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 1bc5b945190c83312f0fc60f06e311fabc403ed0 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Fri, 21 Jun 2024 10:41:49 +0800
Subject: [PATCH v3 2/2] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_counts:
	Number of times inserting a row that iolates a NOT DEFERRABLE unique constraint.
update_differ_counts:
	Number of times updating a row that was previously modified by another origin.
update_missing_counts:
	Number of times that the tuple to be updated is missing.
delete_missing_counts:
	Number of times that the tuple to be deleted is missing.

The conflicts will be tracked only when track_conflict option of the
subscription is enabled. Additionally, update_differ can be detected only
when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  | 52 ++++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |  4 +-
 src/backend/catalog/system_views.sql          |  4 +
 src/backend/replication/logical/conflict.c    |  4 +
 .../utils/activity/pgstat_subscription.c      | 17 ++++
 src/backend/utils/adt/pgstatfuncs.c           | 20 ++++-
 src/include/catalog/pg_proc.dat               |  6 +-
 src/include/pgstat.h                          |  4 +
 src/include/replication/conflict.h            |  2 +
 src/test/regress/expected/rules.out           |  6 +-
 src/test/subscription/t/026_stats.pl          | 77 +++++++++++++++++--
 11 files changed, 178 insertions(+), 18 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index b2ad9b446f..0ceb71f214 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2163,6 +2163,56 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times inserting a row that violates a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times updating a row that was previously modified by another
+       source while applying changes. This conflict is counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated is not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted is not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index ce37fa6490..06bea458a6 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 30393e6d67..182836ac82 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1370,6 +1370,10 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index f24f048054..ca58b708ef 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -75,6 +77,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e8ddb749a7 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,7 +1966,7 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	8
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
@@ -1985,7 +1985,15 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -2005,11 +2013,15 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	/* sync_error_count */
 	values[2] = Int64GetDatum(subentry->sync_error_count);
 
+	/* conflict count */
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		values[3 + i] = Int64GetDatum(subentry->conflict_count[i]);
+
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[7] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[7] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 6a5476d3c4..08bc966a2f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5505,9 +5505,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_differ_count,update_missing_count,delete_missing_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 2136239710..b957e7ad36 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 0bc9db991e..40dcb1d9ad 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -33,6 +33,8 @@ typedef enum
 	CT_DELETE_MISSING,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_MISSING + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 13178e2b3d..80a6857b00 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2141,9 +2141,13 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_differ_count, update_missing_count, delete_missing_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..f81ce66540 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,47 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Update and delete data to test table on the publisher, skipping the
+	# update and delete on the subscriber as there are no data in the test
+	# table.
+	$node_publisher->safe_psql($db, qq(
+		UPDATE $table_name SET a = 2;
+		DELETE FROM $table_name;
+	));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data to test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +171,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +193,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +237,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +258,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +274,15 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From 99e6b4e1eb4e45810862ea0727607cb3d033eed5 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@fujitsu.com>
Date: Fri, 31 May 2024 14:20:45 +0530
Subject: [PATCH v3 1/2] Detect and log conflicts in logical replication

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will
go for confict detection. By default, conflict detection will be off for a
subscription.

When conflict detection is enabled, additional logging is triggered in the
following conflict scenarios:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.

For insert_exists conflict, the log can include origin and commit
timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ conflict can only be detected when track_commit_timestamp is
enabled.
---
 doc/src/sgml/catalogs.sgml                  |   9 +
 doc/src/sgml/logical-replication.sgml       |  23 ++-
 doc/src/sgml/ref/alter_subscription.sgml    |   5 +-
 doc/src/sgml/ref/create_subscription.sgml   |  55 ++++++
 src/backend/catalog/pg_subscription.c       |   1 +
 src/backend/catalog/system_views.sql        |   3 +-
 src/backend/commands/subscriptioncmds.c     |  31 +++-
 src/backend/executor/execIndexing.c         |  14 +-
 src/backend/executor/execReplication.c      | 117 +++++++++++-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 187 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  65 +++++--
 src/bin/pg_dump/pg_dump.c                   |  17 +-
 src/bin/pg_dump/pg_dump.h                   |   1 +
 src/bin/psql/describe.c                     |   6 +-
 src/bin/psql/tab-complete.c                 |  14 +-
 src/include/catalog/pg_subscription.h       |   4 +
 src/include/replication/conflict.h          |  44 +++++
 src/test/regress/expected/subscription.out  | 176 ++++++++++--------
 src/test/regress/sql/subscription.sql       |  15 ++
 src/test/subscription/t/001_rep_changes.pl  |  15 +-
 src/test/subscription/t/013_partition.pl    |  68 ++++---
 src/test/subscription/t/029_on_error.pl     |   5 +-
 src/test/subscription/t/030_origin.pl       |  26 +++
 src/tools/pgindent/typedefs.list            |   1 +
 26 files changed, 752 insertions(+), 152 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index a63cc71efa..a9b6f293ea 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8034,6 +8034,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 746d5bd330..4dd0043414 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1565,7 +1565,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   will simply be skipped, but note that this scenario can be reported in the server log
+   if <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   is enabled.
   </para>
 
   <para>
@@ -1634,6 +1636,25 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.t"
+DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.t" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a
+   local change, users can manually perform a remote-change-win resolution
+   by deleting the local row. Refer to <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for other conflicts that will be logged when enabling <literal>detect_conflict</literal>.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index 476f195622..5f6b83e415 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -228,8 +228,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-disable-on-error"><literal>disable_on_error</literal></link>,
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
-      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>.
+      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..ce37fa6490 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,61 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated is not found.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted is not found.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index efb29adeb3..30393e6d67 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1360,7 +1360,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index e407428dbc..e670d72708 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -70,8 +70,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -97,6 +98,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -159,6 +161,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -316,6 +320,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -603,7 +616,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -710,6 +724,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1146,7 +1162,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_STREAMING | SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1256,6 +1272,13 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..ef522778a2 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,6 +522,11 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		If the 'slot' holds a tuple with valid tid, this tuple will
+ *		be ignored when checking conflict. This can help in scenarios
+ *		where we want to re-check for conflicts after inserting a
+ *		tuple.
  * ----------------------------------------------------------------
  */
 bool
@@ -536,11 +542,9 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	ExprContext *econtext;
 	Datum		values[INDEX_MAX_KEYS];
 	bool		isnull[INDEX_MAX_KEYS];
-	ItemPointerData invalidItemPtr;
 	bool		checkedIndex = false;
 
 	ItemPointerSetInvalid(conflictTid);
-	ItemPointerSetInvalid(&invalidItemPtr);
 
 	/*
 	 * Get information from the result relation info structure.
@@ -629,7 +633,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, &slot->tts_tid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..f01927a933 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -480,6 +481,83 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * Return false if there is no conflict and *conflictslot is set to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned
+ * in *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			goto retry;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			goto retry;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return true;
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +587,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +605,43 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes, &conflict,
+												   conflictindexes, false);
+
+		/* Re-check all the unique indexes for potential conflicts */
+		foreach_oid(uniqueidx, (conflict ? conflictindexes : NIL))
+		{
+			TupleTableSlot *conflictslot;
+
+			/*
+			 * Reports the conflict if any.
+			 *
+			 * Here, we attempt to find the conflict tuple. This operation may
+			 * seem redundant with the unique violation check of indexam, but
+			 * since we perform this only when we are detecting conflict in
+			 * logical replication and encountering potential conflicts with
+			 * any unique index constraints (which should not be frequent), so
+			 * it's ok. Moreover, upon detecting a conflict, we will report an
+			 * ERROR and restart the logical replication, so the additional
+			 * cost of finding the tuple should be acceptable in this case.
+			 */
+			if (list_member_oid(recheckIndexes, uniqueidx) &&
+				FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+			{
+				RepOriginId origin;
+				TimestampTz committs;
+				TransactionId xmin;
+
+				GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+				ReportApplyConflict(ERROR, CT_INSERT_EXISTS, rel, uniqueidx,
+									xmin, origin, committs, conflictslot);
+			}
+		}
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..f24f048054
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,187 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+			{
+				/*
+				 * Bulid the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin %u in transaction %u at %s.",
+									 index_value, get_rel_name(conflictidx), localorigin,
+									 localxmin, timestamptz_to_str(localts));
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			return errdetail("Updating a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	/* Assume the index has been locked */
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b5a80fe3e8..9b889fb78c 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2461,7 +2462,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2664,6 +2668,20 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2681,13 +2699,10 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2821,13 +2836,10 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2994,6 +3006,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3005,16 +3020,28 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
+				 */
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index e324070828..c6b67c692d 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4739,6 +4739,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4811,11 +4812,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4854,6 +4861,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4900,6 +4908,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5140,6 +5150,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 865823868f..02aa4a6f32 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index f67bf0b892..0472fe2e87 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6529,7 +6529,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6597,6 +6597,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d453e224d9..219fac7e71 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..0bc9db991e
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 0f2a25cdc1..a8b0086dd9 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,10 +371,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 --fail - alter of two_phase option not supported.
@@ -383,10 +383,10 @@ ERROR:  unrecognized subscription parameter: "two_phase"
 -- but can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -396,10 +396,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -412,18 +412,42 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 3e5ba4cb8c..a77b196704 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -290,6 +290,21 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,11 +331,12 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
 
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
@@ -352,10 +353,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..7a66a06b51 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,12 +343,12 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
 
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
@@ -372,21 +372,21 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
 
 # Tests for replication using root table identity and schema
 
@@ -773,12 +773,12 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
 
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
@@ -796,15 +796,35 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..496a3c6cd9 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict insert_exists detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(1\) already exists in unique index "tbl_pkey", which was modified by origin \d+ in transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -109,7 +110,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..03dabfeb72 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -26,7 +26,12 @@ my $stderr;
 # node_A
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_A->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
@@ -89,11 +94,32 @@ is( $result, qq(11
 	'Inserted successfully without leading to infinite recursion in bidirectional replication setup'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update a row that
+# was previously modified by a different source.
+###############################################################################
+
+$node_A->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_AB SET (detect_conflict = true);");
+
+$node_B->safe_psql('postgres', "UPDATE tab SET a = 10 WHERE a = 11;");
+
+$node_A->wait_for_log(
+	qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
 $node_A->safe_psql('postgres', "DELETE FROM tab;");
 
 $node_A->wait_for_catchup($subname_BA);
 $node_B->wait_for_catchup($subname_AB);
 
+# The remaining tests no longer test conflict detection.
+$node_A->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_AB SET (detect_conflict = false);");
+
+$node_A->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_A->restart;
+
 ###############################################################################
 # Check that remote data of node_B (that originated from node_C) is not
 # published to node_A.
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 61ad417cde..f42efe12b7 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -465,6 +465,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 2bf4c112198ad0430fbcf499f408aa39de8c4de8 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v4 2/2] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_counts:
	Number of times inserting a row that iolates a NOT DEFERRABLE unique constraint.
update_differ_counts:
	Number of times updating a row that was previously modified by another origin.
update_missing_counts:
	Number of times that the tuple to be updated is missing.
delete_missing_counts:
	Number of times that the tuple to be deleted is missing.
delete_differ_counts:
	Number of times deleting a row that was previously modified by another origin.

The conflicts will be tracked only when track_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  65 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   4 +-
 src/backend/catalog/system_views.sql          |   5 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  22 +++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   2 +
 src/test/regress/expected/rules.out           |   7 +-
 src/test/subscription/t/026_stats.pl          | 102 ++++++++++++++++--
 11 files changed, 220 insertions(+), 18 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 991f629907..92fe4b1011 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,69 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times inserting a row that violates a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times updating a row that was previously modified by another
+       source while applying changes. This conflict is counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated is not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted is not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times deleting a row that was previously modified by another
+       source while applying changes. This conflict is counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index caa523b9bd..2ca7bf20d2 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 30393e6d67..9c7b771ac3 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1370,6 +1370,11 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index b90e64b05b..df5ff0df8e 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -76,6 +78,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..42f2d0f6ef 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,7 +1966,7 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	9
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
@@ -1985,7 +1985,17 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -2005,11 +2015,15 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	/* sync_error_count */
 	values[2] = Int64GetDatum(subentry->sync_error_count);
 
+	/* conflict count */
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		values[3 + i] = Int64GetDatum(subentry->conflict_count[i]);
+
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[8] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[8] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index d4ac578ae6..bd2ad8548d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5505,9 +5505,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 2136239710..b957e7ad36 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index a9f521aaca..a872cfd6dd 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -36,6 +36,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index e12ef4336a..d1dec3d16c 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2142,9 +2142,14 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..6f9d08020c 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,67 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Update and delete data to test table on the publisher, skipping the
+	# update and delete on the subscriber as there are no data in the test
+	# table.
+	$node_publisher->safe_psql($db, qq(
+		UPDATE $table_name SET a = 2;
+		DELETE FROM $table_name;
+	));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data to test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +191,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +214,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +259,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +281,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +298,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From f596cdd2677eb73aaaf11f9b55e0039e77a78b5c Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@fujitsu.com>
Date: Fri, 31 May 2024 14:20:45 +0530
Subject: [PATCH v4 1/2] Detect and log conflicts in logical replication

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will
go for confict detection. By default, conflict detection will be off for a
subscription.

When conflict detection is enabled, additional logging is triggered in the
following conflict scenarios:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists conflict, the log can include origin and commit
timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/catalogs.sgml                  |   9 +
 doc/src/sgml/logical-replication.sgml       |  23 ++-
 doc/src/sgml/ref/alter_subscription.sgml    |   5 +-
 doc/src/sgml/ref/create_subscription.sgml   |  66 +++++++
 src/backend/catalog/pg_subscription.c       |   1 +
 src/backend/catalog/system_views.sql        |   3 +-
 src/backend/commands/subscriptioncmds.c     |  31 +++-
 src/backend/executor/execIndexing.c         |  14 +-
 src/backend/executor/execReplication.c      | 117 +++++++++++-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 191 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  79 ++++++--
 src/bin/pg_dump/pg_dump.c                   |  17 +-
 src/bin/pg_dump/pg_dump.h                   |   1 +
 src/bin/psql/describe.c                     |   6 +-
 src/bin/psql/tab-complete.c                 |  14 +-
 src/include/catalog/pg_subscription.h       |   4 +
 src/include/replication/conflict.h          |  47 +++++
 src/test/regress/expected/subscription.out  | 176 ++++++++++--------
 src/test/regress/sql/subscription.sql       |  15 ++
 src/test/subscription/t/001_rep_changes.pl  |  15 +-
 src/test/subscription/t/013_partition.pl    |  68 ++++---
 src/test/subscription/t/029_on_error.pl     |   5 +-
 src/test/subscription/t/030_origin.pl       |  43 +++++
 src/tools/pgindent/typedefs.list            |   1 +
 26 files changed, 801 insertions(+), 152 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index ccdd24312b..f078d6364b 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1565,7 +1565,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   will simply be skipped, but note that this scenario can be reported in the server log
+   if <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   is enabled.
   </para>
 
   <para>
@@ -1634,6 +1636,25 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.t"
+DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.t" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a
+   local change, users can manually perform a remote-change-win resolution
+   by deleting the local row. Refer to <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for other conflicts that will be logged when enabling <literal>detect_conflict</literal>.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index 476f195622..5f6b83e415 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -228,8 +228,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-disable-on-error"><literal>disable_on_error</literal></link>,
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
-      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>.
+      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..caa523b9bd 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,72 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated is not found.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted is not found.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index efb29adeb3..30393e6d67 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1360,7 +1360,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index e407428dbc..e670d72708 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -70,8 +70,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -97,6 +98,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -159,6 +161,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -316,6 +320,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -603,7 +616,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -710,6 +724,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1146,7 +1162,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_STREAMING | SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1256,6 +1272,13 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..ef522778a2 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,6 +522,11 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		If the 'slot' holds a tuple with valid tid, this tuple will
+ *		be ignored when checking conflict. This can help in scenarios
+ *		where we want to re-check for conflicts after inserting a
+ *		tuple.
  * ----------------------------------------------------------------
  */
 bool
@@ -536,11 +542,9 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	ExprContext *econtext;
 	Datum		values[INDEX_MAX_KEYS];
 	bool		isnull[INDEX_MAX_KEYS];
-	ItemPointerData invalidItemPtr;
 	bool		checkedIndex = false;
 
 	ItemPointerSetInvalid(conflictTid);
-	ItemPointerSetInvalid(&invalidItemPtr);
 
 	/*
 	 * Get information from the result relation info structure.
@@ -629,7 +633,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, &slot->tts_tid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..f01927a933 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -480,6 +481,83 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * Return false if there is no conflict and *conflictslot is set to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned
+ * in *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			goto retry;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			goto retry;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return true;
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +587,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +605,43 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes, &conflict,
+												   conflictindexes, false);
+
+		/* Re-check all the unique indexes for potential conflicts */
+		foreach_oid(uniqueidx, (conflict ? conflictindexes : NIL))
+		{
+			TupleTableSlot *conflictslot;
+
+			/*
+			 * Reports the conflict if any.
+			 *
+			 * Here, we attempt to find the conflict tuple. This operation may
+			 * seem redundant with the unique violation check of indexam, but
+			 * since we perform this only when we are detecting conflict in
+			 * logical replication and encountering potential conflicts with
+			 * any unique index constraints (which should not be frequent), so
+			 * it's ok. Moreover, upon detecting a conflict, we will report an
+			 * ERROR and restart the logical replication, so the additional
+			 * cost of finding the tuple should be acceptable in this case.
+			 */
+			if (list_member_oid(recheckIndexes, uniqueidx) &&
+				FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+			{
+				RepOriginId origin;
+				TimestampTz committs;
+				TransactionId xmin;
+
+				GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+				ReportApplyConflict(ERROR, CT_INSERT_EXISTS, rel, uniqueidx,
+									xmin, origin, committs, conflictslot);
+			}
+		}
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..b90e64b05b
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,191 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+			{
+				/*
+				 * Bulid the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin %u in transaction %u at %s.",
+									 index_value, get_rel_name(conflictidx), localorigin,
+									 localxmin, timestamptz_to_str(localts));
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			return errdetail("Updating a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			return errdetail("Deleting a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	/* Assume the index has been locked */
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b5a80fe3e8..ca08f13189 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2461,7 +2462,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2664,6 +2668,20 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2681,13 +2699,10 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2810,6 +2825,20 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2821,13 +2850,10 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2994,6 +3020,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3005,16 +3034,28 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
+				 */
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index e324070828..c6b67c692d 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4739,6 +4739,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4811,11 +4812,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4854,6 +4861,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4900,6 +4908,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5140,6 +5150,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 865823868f..02aa4a6f32 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index f67bf0b892..0472fe2e87 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6529,7 +6529,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6597,6 +6597,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d453e224d9..219fac7e71 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..a9f521aaca
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,47 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 0f2a25cdc1..a8b0086dd9 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,10 +371,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 --fail - alter of two_phase option not supported.
@@ -383,10 +383,10 @@ ERROR:  unrecognized subscription parameter: "two_phase"
 -- but can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -396,10 +396,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -412,18 +412,42 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 3e5ba4cb8c..a77b196704 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -290,6 +290,21 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,11 +331,12 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
 
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
@@ -352,10 +353,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..7a66a06b51 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,12 +343,12 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
 
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
@@ -372,21 +372,21 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
 
 # Tests for replication using root table identity and schema
 
@@ -773,12 +773,12 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
 
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
@@ -796,15 +796,35 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..496a3c6cd9 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict insert_exists detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(1\) already exists in unique index "tbl_pkey", which was modified by origin \d+ in transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -109,7 +110,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..c8657f5b47 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,44 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/Deleting a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+# The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index e6c1caf649..3ffa941b4d 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -465,6 +465,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 4485d3ac013dcd38ed98bc9afb93b1b4e7ae54c4 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v5 2/2] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_counts:
	Number of times inserting a row that iolates a NOT DEFERRABLE unique constraint.
insert_exists_counts:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_differ_counts:
	Number of times updating a row that was previously modified by another origin.
update_missing_counts:
	Number of times that the tuple to be updated is missing.
delete_missing_counts:
	Number of times that the tuple to be deleted is missing.
delete_differ_counts:
	Number of times deleting a row that was previously modified by another origin.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  78 +++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  35 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 120 +++++++++++++++++-
 11 files changed, 269 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..abe28068a8 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,82 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times inserting a row that violates a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violates a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times updating a row that was previously modified by another
+       source while applying changes. This conflict is counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times deleting a row that was previously modified by another
+       source while applying changes. This conflict is counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index eb51805e81..04f3ba6e9a 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected(displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..5244d8e356 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index b7dc73cfce..4873639dbf 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -78,6 +80,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..850b20509f 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,27 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i + nconflict] = Int64GetDatum(subentry->conflict_count[nconflict]);
+
+	i += CONFLICT_NUM_TYPES;
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 73d9cf8582..6848096b47 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5505,9 +5505,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 6b99bb8aad..ad6619bcd0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 3a7260d3c1..b5e9c79100 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -39,6 +44,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 4c789279e5..3fa03b4d76 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2139,9 +2139,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..deaf71275d 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +232,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +277,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +299,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +316,16 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From 9268838cca52c51a218618287f436fd09a1615a1 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@fujitsu.com>
Date: Fri, 31 May 2024 14:20:45 +0530
Subject: [PATCH v5 1/2] Detect and log conflicts in logical replication

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will
go for confict detection. By default, conflict detection will be off for a
subscription.

When conflict detection is enabled, additional logging is triggered in the
following conflict scenarios:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists conflict, the log can include origin and commit
timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/catalogs.sgml                  |   9 +
 doc/src/sgml/logical-replication.sgml       |  21 ++-
 doc/src/sgml/ref/alter_subscription.sgml    |   5 +-
 doc/src/sgml/ref/create_subscription.sgml   |  84 +++++++++
 src/backend/catalog/pg_subscription.c       |   1 +
 src/backend/catalog/system_views.sql        |   3 +-
 src/backend/commands/subscriptioncmds.c     |  31 +++-
 src/backend/executor/execIndexing.c         |  14 +-
 src/backend/executor/execReplication.c      | 142 +++++++++++++-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 194 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  84 +++++++--
 src/bin/pg_dump/pg_dump.c                   |  17 +-
 src/bin/pg_dump/pg_dump.h                   |   1 +
 src/bin/psql/describe.c                     |   6 +-
 src/bin/psql/tab-complete.c                 |  14 +-
 src/include/catalog/pg_subscription.h       |   4 +
 src/include/replication/conflict.h          |  50 +++++
 src/test/regress/expected/subscription.out  | 176 ++++++++++--------
 src/test/regress/sql/subscription.sql       |  15 ++
 src/test/subscription/t/001_rep_changes.pl  |  15 +-
 src/test/subscription/t/013_partition.pl    |  68 ++++---
 src/test/subscription/t/029_on_error.pl     |   5 +-
 src/test/subscription/t/030_origin.pl       |  43 +++++
 src/tools/pgindent/typedefs.list            |   1 +
 26 files changed, 850 insertions(+), 155 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index ccdd24312b..1c37f63e12 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1565,7 +1565,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   will simply be skipped. Please refer to <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1634,6 +1635,24 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.t"
+DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.t" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a
+   local change, users can manually perform a remote-change-win resolution
+   by deleting the local row.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index 476f195622..5f6b83e415 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -228,8 +228,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-disable-on-error"><literal>disable_on_error</literal></link>,
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
-      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>.
+      <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..eb51805e81 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,90 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the update is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the delete is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index 16d83b3253..512b4273ae 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -70,8 +70,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -97,6 +98,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -159,6 +161,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -316,6 +320,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -603,7 +616,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -710,6 +724,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1148,7 +1164,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_STREAMING | SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1258,6 +1274,13 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..ef522778a2 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,6 +522,11 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		If the 'slot' holds a tuple with valid tid, this tuple will
+ *		be ignored when checking conflict. This can help in scenarios
+ *		where we want to re-check for conflicts after inserting a
+ *		tuple.
  * ----------------------------------------------------------------
  */
 bool
@@ -536,11 +542,9 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	ExprContext *econtext;
 	Datum		values[INDEX_MAX_KEYS];
 	bool		isnull[INDEX_MAX_KEYS];
-	ItemPointerData invalidItemPtr;
 	bool		checkedIndex = false;
 
 	ItemPointerSetInvalid(conflictTid);
-	ItemPointerSetInvalid(&invalidItemPtr);
 
 	/*
 	 * Get information from the result relation info structure.
@@ -629,7 +633,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, &slot->tts_tid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..0680bc86fd 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -480,6 +481,121 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * Return false if there is no conflict and *conflictslot is set to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned
+ * in *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			goto retry;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			goto retry;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return true;
+}
+
+/*
+ * Re-check all the unique indexes in 'recheckIndexes' to see if there are
+ * potential conflicts with the tuple in 'slot'.
+ *
+ * This function is invoked after inserting or updating a tuple that detected
+ * potential conflict tuples. It attempts to find the tuple that conflicts with
+ * the provided tuple. This operation may seem redundant with the unique
+ * violation check of indexam, but since we call this function only when we are
+ * detecting conflict in logical replication and encountering potential
+ * conflicts with any unique index constraints (which should not be frequent),
+ * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
+ * restart the logical replication, so the additional cost of finding the tuple
+ * should be acceptable.
+ */
+static void
+ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Re-check all the unique indexes for potential conflicts */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +625,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +643,17 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes, &conflict,
+												   conflictindexes, false);
+
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +702,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +720,19 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..b7dc73cfce
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,194 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Bulid the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin %u in transaction %u at %s.",
+									 index_value, get_rel_name(conflictidx), localorigin,
+									 localxmin, timestamptz_to_str(localts));
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			return errdetail("Updating a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			return errdetail("Deleting a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	/* Assume the index has been locked */
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index c0bda6269b..c49240a6a4 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2461,7 +2462,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2649,7 +2653,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2664,6 +2668,20 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2671,6 +2689,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2681,13 +2702,10 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2810,6 +2828,20 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2821,13 +2853,10 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2994,6 +3023,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3005,16 +3037,28 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
+				 */
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b8b1888bd3..829f9b3e88 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4760,6 +4760,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4832,11 +4833,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4875,6 +4882,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4921,6 +4929,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5161,6 +5171,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d453e224d9..219fac7e71 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..3a7260d3c1
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 5c2f1ee517..3d8b8c5d32 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,10 +371,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 --fail - alter of two_phase option not supported.
@@ -383,10 +383,10 @@ ERROR:  unrecognized subscription parameter: "two_phase"
 -- but can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -396,10 +396,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -412,18 +412,42 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 3e5ba4cb8c..a77b196704 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -290,6 +290,21 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,11 +331,12 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
 
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
@@ -352,10 +353,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..7a66a06b51 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,12 +343,12 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
 
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
@@ -372,21 +372,21 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
 
 # Tests for replication using root table identity and schema
 
@@ -773,12 +773,12 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
 
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
@@ -796,15 +796,35 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..496a3c6cd9 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict insert_exists detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(1\) already exists in unique index "tbl_pkey", which was modified by origin \d+ in transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -109,7 +110,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..8c929c07c7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,44 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/Deleting a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+# The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index b4d7f9217c..2098ed7467 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 30379de51c6f67c65244c772dfcdadc87986e77e Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v6 2/2] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  80 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  33 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 125 +++++++++++++++++-
 11 files changed, 274 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..e3f8f3708b 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,84 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violates a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index eb51805e81..04f3ba6e9a 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected(displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..5244d8e356 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 4918011a7f..6e2f15cd7d 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -77,6 +79,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e36ddb4cac 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 73d9cf8582..6848096b47 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5505,9 +5505,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 6b99bb8aad..ad6619bcd0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 3a7260d3c1..b5e9c79100 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -39,6 +44,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 4c789279e5..3fa03b4d76 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2139,9 +2139,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..56eafa5ba6 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +233,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +279,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +302,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +320,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From 9b1e0e2442e6a46ef8d910dda98658bcd197ad5c Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 25 Jul 2024 10:06:52 +0800
Subject: [PATCH v6 1/2] Detect and log conflicts in logical replication

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will
go for confict detection. By default, conflict detection will be off for a
subscription.

When conflict detection is enabled, additional logging is triggered in the
following conflict scenarios:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/catalogs.sgml                  |   9 +
 doc/src/sgml/logical-replication.sgml       |  21 +-
 doc/src/sgml/ref/alter_subscription.sgml    |   5 +-
 doc/src/sgml/ref/create_subscription.sgml   |  84 ++++++++
 src/backend/catalog/pg_subscription.c       |   1 +
 src/backend/catalog/system_views.sql        |   3 +-
 src/backend/commands/subscriptioncmds.c     |  54 ++++-
 src/backend/executor/execIndexing.c         |  14 +-
 src/backend/executor/execReplication.c      | 221 ++++++++++++++------
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 193 +++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  91 ++++++--
 src/bin/pg_dump/pg_dump.c                   |  17 +-
 src/bin/pg_dump/pg_dump.h                   |   1 +
 src/bin/psql/describe.c                     |   6 +-
 src/bin/psql/tab-complete.c                 |  14 +-
 src/include/catalog/pg_subscription.h       |   4 +
 src/include/replication/conflict.h          |  50 +++++
 src/test/regress/expected/subscription.out  | 188 ++++++++++-------
 src/test/regress/sql/subscription.sql       |  19 ++
 src/test/subscription/t/001_rep_changes.pl  |  15 +-
 src/test/subscription/t/013_partition.pl    |  68 +++---
 src/test/subscription/t/029_on_error.pl     |  13 +-
 src/test/subscription/t/030_origin.pl       |  43 ++++
 src/tools/pgindent/typedefs.list            |   1 +
 26 files changed, 921 insertions(+), 216 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..d236d8530c 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1580,7 +1580,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   will simply be skipped. Please refer to <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1649,6 +1650,24 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.t"
+DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.t" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a
+   local change, users can manually perform a remote-change-win resolution
+   by deleting the local row.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index fdc648d007..dfbe25b59e 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -235,8 +235,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
       <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>.
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>,
+      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..eb51805e81 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,90 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the update is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the delete is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index d124bfe55c..24f9430fb1 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -14,6 +14,7 @@
 
 #include "postgres.h"
 
+#include "access/commit_ts.h"
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/twophase.h"
@@ -71,8 +72,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -98,6 +100,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -112,7 +115,7 @@ static List *merge_publications(List *oldpublist, List *newpublist, bool addpub,
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
 static void CheckAlterSubOption(Subscription *sub, const char *option,
 								bool slot_needs_update, bool isTopLevel);
-
+static void check_conflict_detection(void);
 
 /*
  * Common option parsing function for CREATE and ALTER SUBSCRIPTION commands.
@@ -162,6 +165,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -307,6 +312,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -594,7 +608,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -639,6 +654,9 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 				 errmsg("password_required=false is superuser-only"),
 				 errhint("Subscriptions with the password_required option set to false may only be created or modified by the superuser.")));
 
+	if (opts.detectconflict)
+		check_conflict_detection();
+
 	/*
 	 * If built with appropriate switch, whine when regression-testing
 	 * conventions for subscription names are violated.
@@ -701,6 +719,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1196,7 +1216,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1356,6 +1376,16 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+
+					if (opts.detectconflict)
+						check_conflict_detection();
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
@@ -2536,3 +2566,17 @@ defGetStreamingMode(DefElem *def)
 					def->defname)));
 	return LOGICALREP_STREAM_OFF;	/* keep compiler quiet */
 }
+
+/*
+ * Report a warning about incomplete conflict detection if
+ * track_commit_timestamp is disabled.
+ */
+static void
+check_conflict_detection(void)
+{
+	if (!track_commit_timestamp)
+		ereport(WARNING,
+				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				errmsg("conflict detection could be incomplete due to disabled track_commit_timestamp"),
+				errdetail("Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged."));
+}
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..ef522778a2 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,6 +522,11 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		If the 'slot' holds a tuple with valid tid, this tuple will
+ *		be ignored when checking conflict. This can help in scenarios
+ *		where we want to re-check for conflicts after inserting a
+ *		tuple.
  * ----------------------------------------------------------------
  */
 bool
@@ -536,11 +542,9 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	ExprContext *econtext;
 	Datum		values[INDEX_MAX_KEYS];
 	bool		isnull[INDEX_MAX_KEYS];
-	ItemPointerData invalidItemPtr;
 	bool		checkedIndex = false;
 
 	ItemPointerSetInvalid(conflictTid);
-	ItemPointerSetInvalid(&invalidItemPtr);
 
 	/*
 	 * Get information from the result relation info structure.
@@ -629,7 +633,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, &slot->tts_tid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..f4e3d2aa09 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool	refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,95 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * If no conflict is found, return false and set *conflictslot to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned in
+ * *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Re-check all the unique indexes in 'recheckIndexes' to see if there are
+ * potential conflicts with the tuple in 'slot'.
+ *
+ * This function is invoked after inserting or updating a tuple that detected
+ * potential conflict tuples. It attempts to find the tuple that conflicts with
+ * the provided tuple. This operation may seem redundant with the unique
+ * violation check of indexam, but since we call this function only when we are
+ * detecting conflict in logical replication and encountering potential
+ * conflicts with any unique index constraints (which should not be frequent),
+ * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
+ * restart the logical replication, so the additional cost of finding the tuple
+ * should be acceptable.
+ */
+static void
+ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Re-check all the unique indexes for potential conflicts */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +592,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +610,17 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes, &conflict,
+												   conflictindexes, false);
+
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +669,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +687,19 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..4918011a7f
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,193 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Bulid the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin %u in transaction %u at %s.",
+									 index_value, get_rel_name(conflictidx), localorigin,
+									 localxmin, timestamptz_to_str(localts));
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			return errdetail("Updating a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			return errdetail("Deleting a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	/* Assume the index has been locked */
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ec96b5fe85..1008510240 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,7 +2650,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2661,6 +2665,20 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 */
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2686,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2678,13 +2699,10 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2825,25 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
+		 *
+		 * For cross-partition update, we skip detecting the delete_differ
+		 * conflict since it should have been done in
+		 * apply_handle_tuple_routing().
+		 */
+		if (MySubscription->detectconflict &&
+			(!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2855,10 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2991,6 +3025,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3002,16 +3039,28 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
+				 */
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3039,7 +3088,7 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, false);
+					ExecOpenIndices(partrelinfo, MySubscription->detectconflict);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b8b1888bd3..829f9b3e88 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4760,6 +4760,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4832,11 +4833,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4875,6 +4882,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4921,6 +4929,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5161,6 +5171,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 891face1b6..086e135f65 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..3a7260d3c1
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 17d48b1685..c5ccc7b7bf 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,19 +371,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- we can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -393,10 +393,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -409,18 +409,54 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 007c9e7037..b3f2ab1684 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -287,6 +287,25 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,11 +331,12 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
 
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
@@ -352,10 +353,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..7a66a06b51 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,12 +343,12 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
 
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
@@ -372,21 +372,21 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
 
 # Tests for replication using root table identity and schema
 
@@ -773,12 +773,12 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
 
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
@@ -796,15 +796,35 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..ec1a48d0f6 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict .* detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by origin \d+ in transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -109,7 +111,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..97c2057275 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,44 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict update_differ detected on relation "public.tab".*\n.*DETAIL:.* Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict delete_differ detected on relation "public.tab".*\n.*DETAIL:.* Deleting a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+# The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index b4d7f9217c..2098ed7467 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 32d712bf6428f747912b695d3b4b3a12026fa748 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v7 3/3] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  80 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  33 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 125 +++++++++++++++++-
 11 files changed, 274 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..7b93334967 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,84 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index d07201abec..67c7c9fcbc 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected(displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..5244d8e356 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 4918011a7f..6e2f15cd7d 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -77,6 +79,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e36ddb4cac 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 06b2f4ba66..12976efc11 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5532,9 +5532,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 6b99bb8aad..ad6619bcd0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 3a7260d3c1..b5e9c79100 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -39,6 +44,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 5201280669..3c1154b14b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2140,9 +2140,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..56eafa5ba6 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +233,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +279,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +302,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +320,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From 61550286a80ef8fa3abc33c2b49914e28908d1e3 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Mon, 29 Jul 2024 11:14:37 +0800
Subject: [PATCH v7 1/3] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/logical-replication.sgml       |  90 +++++++-
 src/backend/executor/execIndexing.c         |  14 +-
 src/backend/executor/execReplication.c      | 237 +++++++++++++++-----
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 193 ++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  82 +++++--
 src/include/replication/conflict.h          |  50 +++++
 src/test/subscription/t/001_rep_changes.pl  |  10 +-
 src/test/subscription/t/013_partition.pl    |  51 ++---
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++++
 src/tools/pgindent/typedefs.list            |   1 +
 13 files changed, 661 insertions(+), 127 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..830c7a9b02 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1583,6 +1583,86 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    will simply be skipped.
   </para>
 
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   scenarios:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another
+       partition constraint resulting in the row being inserted into a
+       new partition, the <literal>insert_exists</literal> conflict may
+       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the update is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that this
+       conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the delete is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+  </para>
+
   <para>
    Logical replication operations are performed with the privileges of the role
    which owns the subscription.  Permissions failures on target tables will
@@ -1609,8 +1689,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict insert_exists detected on relation "test_pkey"
+DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1716,12 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the log as well. Users can use these
+   information to make decisions on whether to retain the local change or adopt
+   the remote alteration. For instance, the origin in above log indicates that
+   the existing row was modified by a local change, users can manually perform
+   a remote-change-win resolution by deleting the local row.
   </para>
 
   <para>
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..ef522778a2 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,6 +522,11 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		If the 'slot' holds a tuple with valid tid, this tuple will
+ *		be ignored when checking conflict. This can help in scenarios
+ *		where we want to re-check for conflicts after inserting a
+ *		tuple.
  * ----------------------------------------------------------------
  */
 bool
@@ -536,11 +542,9 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 	ExprContext *econtext;
 	Datum		values[INDEX_MAX_KEYS];
 	bool		isnull[INDEX_MAX_KEYS];
-	ItemPointerData invalidItemPtr;
 	bool		checkedIndex = false;
 
 	ItemPointerSetInvalid(conflictTid);
-	ItemPointerSetInvalid(&invalidItemPtr);
 
 	/*
 	 * Get information from the result relation info structure.
@@ -629,7 +633,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, &slot->tts_tid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..4af0040411 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,95 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * If no conflict is found, return false and set *conflictslot to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned in
+ * *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Re-check all the unique indexes in 'recheckIndexes' to see if there are
+ * potential conflicts with the tuple in 'slot'.
+ *
+ * This function is invoked after inserting or updating a tuple that detected
+ * potential conflict tuples. It attempts to find the tuple that conflicts with
+ * the provided tuple. This operation may seem redundant with the unique
+ * violation check of indexam, but since we call this function only when we are
+ * detecting conflict in logical replication and encountering potential
+ * conflicts with any unique index constraints (which should not be frequent),
+ * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
+ * restart the logical replication, so the additional cost of finding the tuple
+ * should be acceptable.
+ */
+static void
+ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Re-check all the unique indexes for potential conflicts */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +592,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +610,28 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Rechecks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * perform an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +680,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +698,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to ReCheckConflictIndexes() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..4918011a7f
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,193 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Bulid the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin %u in transaction %u at %s.",
+									 index_value, get_rel_name(conflictidx), localorigin,
+									 localxmin, timestamptz_to_str(localts));
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			return errdetail("Updating a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			return errdetail("Deleting a row that was modified by a different origin %u in transaction %u at %s.",
+							 localorigin, localxmin, timestamptz_to_str(localts));
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	/* Assume the index has been locked */
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ec96b5fe85..505db3e13c 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,7 +2648,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2661,6 +2663,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 */
+		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2683,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2678,13 +2695,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2820,24 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 *
+		 * For cross-partition update, we skip detecting the delete_differ
+		 * conflict since it should have been done in
+		 * apply_handle_tuple_routing().
+		 */
+		if ((!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2849,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2991,6 +3018,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3002,16 +3032,25 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										partrel, InvalidOid,
+										InvalidTransactionId,
+										InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * Check whether the local tuple was modified by a different
+				 * origin. If detected, report the conflict.
+				 */
+				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3039,7 +3078,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, false);
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(relinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..3a7260d3c1
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..79cbed2e5b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,12 +331,6 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -352,10 +346,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..8517c189d4 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,30 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..3e27a1a7dc 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict .* detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by origin \d+ in transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..a368818b21 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict update_differ detected on relation "public.tab".*\n.*DETAIL:.* Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict delete_differ detected on relation "public.tab".*\n.*DETAIL:.* Deleting a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 3deb6113b8..ae1db1a759 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 27c7ed549fcf0a79f3ec5a8680178fd5ae863a8d Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Mon, 29 Jul 2024 14:02:53 +0800
Subject: [PATCH v7 2/3] Add a detect_conflict option to subscriptions

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will go
for confict detection and provide additional logging information. To avoid the
potential overhead introduced by conflict detection, detect_conflict will be
off for a subscription by default.
---
 doc/src/sgml/catalogs.sgml                 |   9 +
 doc/src/sgml/logical-replication.sgml      | 112 +++---------
 doc/src/sgml/ref/alter_subscription.sgml   |   5 +-
 doc/src/sgml/ref/create_subscription.sgml  |  89 ++++++++++
 src/backend/catalog/pg_subscription.c      |   1 +
 src/backend/catalog/system_views.sql       |   3 +-
 src/backend/commands/subscriptioncmds.c    |  54 +++++-
 src/backend/replication/logical/worker.c   |  58 ++++---
 src/bin/pg_dump/pg_dump.c                  |  17 +-
 src/bin/pg_dump/pg_dump.h                  |   1 +
 src/bin/psql/describe.c                    |   6 +-
 src/bin/psql/tab-complete.c                |  14 +-
 src/include/catalog/pg_subscription.h      |   4 +
 src/test/regress/expected/subscription.out | 188 ++++++++++++---------
 src/test/regress/sql/subscription.sql      |  19 +++
 src/test/subscription/t/001_rep_changes.pl |   7 +
 src/test/subscription/t/013_partition.pl   |  23 +++
 src/test/subscription/t/029_on_error.pl    |   2 +-
 src/test/subscription/t/030_origin.pl      |   7 +-
 19 files changed, 413 insertions(+), 206 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 830c7a9b02..34b420cfcf 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1580,87 +1580,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
-  </para>
-
-  <para>
-   Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   scenarios:
-   <variablelist>
-    <varlistentry>
-     <term><literal>insert_exists</literal></term>
-     <listitem>
-      <para>
-       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_exists</literal></term>
-     <listitem>
-      <para>
-       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually. Note that when updating a
-       partitioned table, if the updated row value satisfies another
-       partition constraint resulting in the row being inserted into a
-       new partition, the <literal>insert_exists</literal> conflict may
-       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_differ</literal></term>
-     <listitem>
-      <para>
-       Updating a row that was previously modified by another origin.
-       Note that this conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the update is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be updated was not found. The update will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be deleted was not found. The delete will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_differ</literal></term>
-     <listitem>
-      <para>
-       Deleting a row that was previously modified by another origin. Note that this
-       conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the delete is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-   </variablelist>
+   will simply be skipped. Please refer to
+   <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1689,8 +1611,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  conflict insert_exists detected on relation "test_pkey"
-DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
+ERROR:  duplicate key value violates unique constraint "test_pkey"
+DETAIL:  Key (c)=(1) already exists.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1716,12 +1638,6 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
-   The additional details regarding conflicting rows, such as their origin and
-   commit timestamp can be seen in the log as well. Users can use these
-   information to make decisions on whether to retain the local change or adopt
-   the remote alteration. For instance, the origin in above log indicates that
-   the existing row was modified by a local change, users can manually perform
-   a remote-change-win resolution by deleting the local row.
   </para>
 
   <para>
@@ -1735,6 +1651,24 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.t"
+DETAIL:  Key (a)=(1) already exists in unique index "t_pkey", which was modified by origin 0 in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.t" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a
+   local change, users can manually perform a remote-change-win resolution
+   by deleting the local row.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index fdc648d007..dfbe25b59e 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -235,8 +235,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
       <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>.
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>,
+      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..d07201abec 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,95 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually. Note that when updating a
+              partitioned table, if the updated row value satisfies another
+              partition constraint resulting in the row being inserted into a
+              new partition, the <literal>insert_exists</literal> conflict may
+              arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the update is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the delete is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index d124bfe55c..a949d246df 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -14,6 +14,7 @@
 
 #include "postgres.h"
 
+#include "access/commit_ts.h"
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/twophase.h"
@@ -71,8 +72,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -98,6 +100,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -112,6 +115,7 @@ static List *merge_publications(List *oldpublist, List *newpublist, bool addpub,
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
 static void CheckAlterSubOption(Subscription *sub, const char *option,
 								bool slot_needs_update, bool isTopLevel);
+static void check_conflict_detection(void);
 
 
 /*
@@ -162,6 +166,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -307,6 +313,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -594,7 +609,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -639,6 +655,9 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 				 errmsg("password_required=false is superuser-only"),
 				 errhint("Subscriptions with the password_required option set to false may only be created or modified by the superuser.")));
 
+	if (opts.detectconflict)
+		check_conflict_detection();
+
 	/*
 	 * If built with appropriate switch, whine when regression-testing
 	 * conventions for subscription names are violated.
@@ -701,6 +720,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1196,7 +1217,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1356,6 +1377,16 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+
+					if (opts.detectconflict)
+						check_conflict_detection();
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
@@ -2536,3 +2567,18 @@ defGetStreamingMode(DefElem *def)
 					def->defname)));
 	return LOGICALREP_STREAM_OFF;	/* keep compiler quiet */
 }
+
+/*
+ * Report a warning about incomplete conflict detection if
+ * track_commit_timestamp is disabled.
+ */
+static void
+check_conflict_detection(void)
+{
+	if (!track_commit_timestamp)
+		ereport(WARNING,
+				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				errmsg("conflict detection could be incomplete due to disabled track_commit_timestamp"),
+				errdetail("Conflicts update_differ and delete_differ cannot be detected, "
+						  "and the origin and commit timestamp for the local row will not be logged."));
+}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 505db3e13c..df9a9eb0d7 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2459,8 +2459,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, true);
-	InitConflictIndexes(relinfo);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2648,7 +2650,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, true);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2668,10 +2670,11 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 */
-		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2683,7 +2686,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
-		InitConflictIndexes(relinfo);
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
 
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
@@ -2696,8 +2700,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2825,14 +2830,15 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 *
 		 * For cross-partition update, we skip detecting the delete_differ
 		 * conflict since it should have been done in
 		 * apply_handle_tuple_routing().
 		 */
-		if ((!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+		if (MySubscription->detectconflict &&
+			(!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
 			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
@@ -2850,8 +2856,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -3033,19 +3040,22 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
 					 */
-					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
-										partrel, InvalidOid,
-										InvalidTransactionId,
-										InvalidRepOriginId, 0, NULL);
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
 
 					return;
 				}
 
 				/*
-				 * Check whether the local tuple was modified by a different
-				 * origin. If detected, report the conflict.
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
 				 */
-				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)
 					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
 										InvalidOid, localxmin, localorigin,
@@ -3078,8 +3088,10 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, true);
-					InitConflictIndexes(relinfo);
+					ExecOpenIndices(partrelinfo, MySubscription->detectconflict);
+
+					if (MySubscription->detectconflict)
+						InitConflictIndexes(relinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b8b1888bd3..829f9b3e88 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4760,6 +4760,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4832,11 +4833,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4875,6 +4882,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4921,6 +4929,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5161,6 +5171,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 891face1b6..086e135f65 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 17d48b1685..118f207df5 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,19 +371,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- we can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -393,10 +393,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -409,18 +409,54 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 007c9e7037..b3f2ab1684 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -287,6 +287,25 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 79cbed2e5b..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,6 +331,13 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
+
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 8517c189d4..b3044a2651 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,6 +343,13 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
+
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -377,6 +384,10 @@ ok( $logfile =~
 	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
+
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -762,6 +773,13 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
+
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -800,6 +818,11 @@ ok( $logfile =~
 	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified by a different origin [0-9]+ in transaction [0-9]+ at .*/,
 	'updating a tuple that was modified by a different origin');
 
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
 $node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_subscriber1->restart;
 
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 3e27a1a7dc..ec1a48d0f6 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -111,7 +111,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index a368818b21..69a1ef03a1 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -149,7 +149,9 @@ is($result, qq(),
 # delete a row that was previously modified by a different source.
 ###############################################################################
 
-$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
 
 $node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
 
@@ -183,6 +185,9 @@ $node_B->wait_for_log(
 );
 
 # The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
 $node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_B->restart;
 
-- 
2.30.0.windows.2

From 447c4acbc0157af1dfde84970d19f8de5ac7d67a Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Tue, 30 Jul 2024 20:43:55 +0800
Subject: [PATCH v8 2/3] Add a detect_conflict option to subscriptions

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will go
for confict detection and provide additional logging information. To avoid the
potential overhead introduced by conflict detection, detect_conflict will be
off for a subscription by default.
---
 doc/src/sgml/catalogs.sgml                 |   9 +
 doc/src/sgml/logical-replication.sgml      | 115 +++----------
 doc/src/sgml/ref/alter_subscription.sgml   |   5 +-
 doc/src/sgml/ref/create_subscription.sgml  |  89 ++++++++++
 src/backend/catalog/pg_subscription.c      |   1 +
 src/backend/catalog/system_views.sql       |   3 +-
 src/backend/commands/subscriptioncmds.c    |  54 +++++-
 src/backend/replication/logical/worker.c   |  58 ++++---
 src/bin/pg_dump/pg_dump.c                  |  17 +-
 src/bin/pg_dump/pg_dump.h                  |   1 +
 src/bin/psql/describe.c                    |   6 +-
 src/bin/psql/tab-complete.c                |  14 +-
 src/include/catalog/pg_subscription.h      |   4 +
 src/test/regress/expected/subscription.out | 188 ++++++++++++---------
 src/test/regress/sql/subscription.sql      |  19 +++
 src/test/subscription/t/001_rep_changes.pl |   7 +
 src/test/subscription/t/013_partition.pl   |  23 +++
 src/test/subscription/t/029_on_error.pl    |   2 +-
 src/test/subscription/t/030_origin.pl      |   7 +-
 19 files changed, 413 insertions(+), 209 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 8f69844b6a..5489b400ee 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1580,87 +1580,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
-  </para>
-
-  <para>
-   Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   scenarios:
-   <variablelist>
-    <varlistentry>
-     <term><literal>insert_exists</literal></term>
-     <listitem>
-      <para>
-       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_exists</literal></term>
-     <listitem>
-      <para>
-       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually. Note that when updating a
-       partitioned table, if the updated row value satisfies another
-       partition constraint resulting in the row being inserted into a
-       new partition, the <literal>insert_exists</literal> conflict may
-       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_differ</literal></term>
-     <listitem>
-      <para>
-       Updating a row that was previously modified by another origin.
-       Note that this conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the update is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be updated was not found. The update will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be deleted was not found. The delete will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_differ</literal></term>
-     <listitem>
-      <para>
-       Deleting a row that was previously modified by another origin. Note that this
-       conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the delete is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-   </variablelist>
+   will simply be skipped. Please refer to
+   <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1689,8 +1611,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  conflict insert_exists detected on relation "public.test"
-DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+ERROR:  duplicate key value violates unique constraint "test_pkey"
+DETAIL:  Key (c)=(1) already exists.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1716,15 +1638,6 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
-   The additional details regarding conflicting rows, such as their origin and
-   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
-   log. But note that this information is only available when
-   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-   is enabled. Users can use these information to make decisions on whether to
-   retain the local change or adopt the remote alteration. For instance, the
-   origin in above log indicates that the existing row was modified by a local
-   change, users can manually perform a remote-change-win resolution by
-   deleting the local row.
   </para>
 
   <para>
@@ -1738,6 +1651,24 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.test" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a
+   local change, users can manually perform a remote-change-win resolution
+   by deleting the local row.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index fdc648d007..dfbe25b59e 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -235,8 +235,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
       <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>.
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>,
+      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..d07201abec 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,95 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually. Note that when updating a
+              partitioned table, if the updated row value satisfies another
+              partition constraint resulting in the row being inserted into a
+              new partition, the <literal>insert_exists</literal> conflict may
+              arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the update is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the delete is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index d124bfe55c..a949d246df 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -14,6 +14,7 @@
 
 #include "postgres.h"
 
+#include "access/commit_ts.h"
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/twophase.h"
@@ -71,8 +72,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -98,6 +100,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -112,6 +115,7 @@ static List *merge_publications(List *oldpublist, List *newpublist, bool addpub,
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
 static void CheckAlterSubOption(Subscription *sub, const char *option,
 								bool slot_needs_update, bool isTopLevel);
+static void check_conflict_detection(void);
 
 
 /*
@@ -162,6 +166,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -307,6 +313,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -594,7 +609,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -639,6 +655,9 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 				 errmsg("password_required=false is superuser-only"),
 				 errhint("Subscriptions with the password_required option set to false may only be created or modified by the superuser.")));
 
+	if (opts.detectconflict)
+		check_conflict_detection();
+
 	/*
 	 * If built with appropriate switch, whine when regression-testing
 	 * conventions for subscription names are violated.
@@ -701,6 +720,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1196,7 +1217,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1356,6 +1377,16 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+
+					if (opts.detectconflict)
+						check_conflict_detection();
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
@@ -2536,3 +2567,18 @@ defGetStreamingMode(DefElem *def)
 					def->defname)));
 	return LOGICALREP_STREAM_OFF;	/* keep compiler quiet */
 }
+
+/*
+ * Report a warning about incomplete conflict detection if
+ * track_commit_timestamp is disabled.
+ */
+static void
+check_conflict_detection(void)
+{
+	if (!track_commit_timestamp)
+		ereport(WARNING,
+				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				errmsg("conflict detection could be incomplete due to disabled track_commit_timestamp"),
+				errdetail("Conflicts update_differ and delete_differ cannot be detected, "
+						  "and the origin and commit timestamp for the local row will not be logged."));
+}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 0541e8a165..6575b040a7 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2459,8 +2459,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, true);
-	InitConflictIndexes(relinfo);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2648,7 +2650,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, true);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2668,10 +2670,11 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 */
-		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2683,7 +2686,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
-		InitConflictIndexes(relinfo);
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
 
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
@@ -2696,8 +2700,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2825,14 +2830,15 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 *
 		 * For cross-partition update, we skip detecting the delete_differ
 		 * conflict since it should have been done in
 		 * apply_handle_tuple_routing().
 		 */
-		if ((!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+		if (MySubscription->detectconflict &&
+			(!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
 			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
@@ -2850,8 +2856,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -3033,19 +3040,22 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
 					 */
-					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
-										partrel, InvalidOid,
-										InvalidTransactionId,
-										InvalidRepOriginId, 0, NULL);
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
 
 					return;
 				}
 
 				/*
-				 * Check whether the local tuple was modified by a different
-				 * origin. If detected, report the conflict.
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
 				 */
-				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)
 					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
 										InvalidOid, localxmin, localorigin,
@@ -3078,8 +3088,10 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, true);
-					InitConflictIndexes(partrelinfo);
+					ExecOpenIndices(partrelinfo, MySubscription->detectconflict);
+
+					if (MySubscription->detectconflict)
+						InitConflictIndexes(partrelinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b8b1888bd3..829f9b3e88 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4760,6 +4760,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4832,11 +4833,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4875,6 +4882,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4921,6 +4929,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5161,6 +5171,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 891face1b6..086e135f65 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3363,9 +3364,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 17d48b1685..118f207df5 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,19 +371,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- we can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -393,10 +393,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -409,18 +409,54 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 007c9e7037..b3f2ab1684 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -287,6 +287,25 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 79cbed2e5b..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,6 +331,13 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
+
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 896985d85b..a3effed937 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,6 +343,13 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
+
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -377,6 +384,10 @@ ok( $logfile =~
 	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
+
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -762,6 +773,13 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
+
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -800,6 +818,11 @@ ok( $logfile =~
 	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
 	'updating a tuple that was modified by a different origin');
 
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
 $node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_subscriber1->restart;
 
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index ac7c8bbe7c..b71d0c3400 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -111,7 +111,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 5a22413464..6bc4474d15 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -149,7 +149,9 @@ is($result, qq(),
 # delete a row that was previously modified by a different source.
 ###############################################################################
 
-$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
 
 $node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
 
@@ -183,6 +185,9 @@ $node_B->wait_for_log(
 );
 
 # The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
 $node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_B->restart;
 
-- 
2.30.0.windows.2

From aa3b35f14895ce1e9e184432eefd4ddf73d04090 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Mon, 29 Jul 2024 11:14:37 +0800
Subject: [PATCH v8] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/logical-replication.sgml       |  93 +++++++-
 src/backend/executor/execIndexing.c         |  13 +-
 src/backend/executor/execReplication.c      | 238 ++++++++++++++-----
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 247 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  82 +++++--
 src/include/executor/executor.h             |   1 +
 src/include/replication/conflict.h          |  50 ++++
 src/test/subscription/t/001_rep_changes.pl  |  10 +-
 src/test/subscription/t/013_partition.pl    |  51 ++--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++++
 src/tools/pgindent/typedefs.list            |   1 +
 15 files changed, 724 insertions(+), 127 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..8f69844b6a 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1583,6 +1583,86 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    will simply be skipped.
   </para>
 
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   scenarios:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another
+       partition constraint resulting in the row being inserted into a
+       new partition, the <literal>insert_exists</literal> conflict may
+       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the update is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that this
+       conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the delete is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+  </para>
+
   <para>
    Logical replication operations are performed with the privileges of the role
    which owns the subscription.  Permissions failures on target tables will
@@ -1609,8 +1689,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1716,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled. Users can use these information to make decisions on whether to
+   retain the local change or adopt the remote alteration. For instance, the
+   origin in above log indicates that the existing row was modified by a local
+   change, users can manually perform a remote-change-win resolution by
+   deleting the local row.
   </para>
 
   <para>
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..bdfc7cf7a6 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -521,12 +522,16 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *		possible that a conflicting tuple is inserted immediately
  *		after this returns.  But this can be used for a pre-check
  *		before insertion.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..f4b605970d 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,96 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * If no conflict is found, return false and set *conflictslot to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned in
+ * *conflictslot.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Re-check all the unique indexes in 'recheckIndexes' to see if there are
+ * potential conflicts with the tuple in 'slot'.
+ *
+ * This function is invoked after inserting or updating a tuple that detected
+ * potential conflict tuples. It attempts to find the tuple that conflicts with
+ * the provided tuple. This operation may seem redundant with the unique
+ * violation check of indexam, but since we call this function only when we are
+ * detecting conflict in logical replication and encountering potential
+ * conflicts with any unique index constraints (which should not be frequent),
+ * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
+ * restart the logical replication, so the additional cost of finding the tuple
+ * should be acceptable.
+ */
+static void
+ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Re-check all the unique indexes for potential conflicts */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +593,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +611,28 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Rechecks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * perform an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +681,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +699,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to ReCheckConflictIndexes() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..287f62f3ba
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,247 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Build the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+				{
+					char	   *origin_name;
+
+					if (localorigin == InvalidRepOriginId)
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified locally in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+					else if (replorigin_by_oid(localorigin, true, &origin_name))
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin \"%s\" in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx), origin_name,
+										 localxmin, timestamptz_to_str(localts));
+
+					/*
+					 * The origin which modified the row has been dropped.
+					 * This situation may occur if the origin was created by a
+					 * different apply worker, but its associated subscription
+					 * and origin were dropped after updating the row, or if
+					 * the origin was manually dropped by the user.
+					 */
+					else
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by a non-existent origin in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+				}
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Updating a row that was modified locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Updating a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Updating a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Deleting a row that was modified by locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Deleting a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Deleting a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ec96b5fe85..0541e8a165 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,7 +2648,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2661,6 +2663,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 */
+		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2683,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2678,13 +2695,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2820,24 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 *
+		 * For cross-partition update, we skip detecting the delete_differ
+		 * conflict since it should have been done in
+		 * apply_handle_tuple_routing().
+		 */
+		if ((!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2849,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2991,6 +3018,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3002,16 +3032,25 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										partrel, InvalidOid,
+										InvalidTransactionId,
+										InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * Check whether the local tuple was modified by a different
+				 * origin. If detected, report the conflict.
+				 */
+				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3039,7 +3078,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, false);
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..3d5383c056 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -636,6 +636,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..3a7260d3c1
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..79cbed2e5b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,12 +331,6 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -352,10 +346,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..896985d85b 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,30 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..ac7c8bbe7c 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict .* detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by .*origin.* transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..5a22413464 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict update_differ detected on relation "public.tab".*\n.*DETAIL:.* Updating a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict delete_differ detected on relation "public.tab".*\n.*DETAIL:.* Deleting a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index b4d7f9217c..2098ed7467 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.31.1

From 6759a8021e4e3085b677ecd775f780322636ce2f Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v8 3/3] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  80 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  33 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 125 +++++++++++++++++-
 11 files changed, 274 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..7b93334967 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,84 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index d07201abec..67c7c9fcbc 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected (displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..5244d8e356 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index b39929934e..e33c8085e2 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -80,6 +82,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e36ddb4cac 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 06b2f4ba66..12976efc11 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5532,9 +5532,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 6b99bb8aad..ad6619bcd0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 3a7260d3c1..b5e9c79100 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -39,6 +44,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 5201280669..3c1154b14b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2140,9 +2140,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..56eafa5ba6 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +233,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +279,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +302,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +320,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From 0484caba00988fde08f270a2660ec8a43d26f05d Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v9 3/3] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  80 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  33 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 125 +++++++++++++++++-
 11 files changed, 274 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..7b93334967 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,84 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index c406ae0fd6..681d94d38d 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected (displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..5244d8e356 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 287f62f3ba..b9a7120d0e 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -80,6 +82,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e36ddb4cac 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 54b50ee5d6..edf4cc6486 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5538,9 +5538,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 6b99bb8aad..ad6619bcd0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 3a7260d3c1..b5e9c79100 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -39,6 +44,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 5201280669..3c1154b14b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2140,9 +2140,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..56eafa5ba6 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +233,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +279,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +302,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +320,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From e65b3e38b720ac2e62948d62614990443861f502 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Mon, 29 Jul 2024 11:14:37 +0800
Subject: [PATCH v9 1/3] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/logical-replication.sgml       |  93 +++++++-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execReplication.c      | 239 ++++++++++++++-----
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 247 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  82 +++++--
 src/include/executor/executor.h             |   1 +
 src/include/replication/conflict.h          |  50 ++++
 src/test/subscription/t/001_rep_changes.pl  |  10 +-
 src/test/subscription/t/013_partition.pl    |  51 ++--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++++
 src/tools/pgindent/typedefs.list            |   1 +
 16 files changed, 730 insertions(+), 131 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..c1f6f1aaa8 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1583,6 +1583,86 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    will simply be skipped.
   </para>
 
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   scenarios:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another
+       partition constraint resulting in the row being inserted into a
+       new partition, the <literal>insert_exists</literal> conflict may
+       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the update is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that this
+       conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the delete is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+  </para>
+
   <para>
    Logical replication operations are performed with the privileges of the role
    which owns the subscription.  Permissions failures on target tables will
@@ -1609,8 +1689,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1716,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled. Users can use these information to make decisions on whether to
+   retain the local change or adopt the remote alteration. For instance, the
+   <literal>DETAIL</literal> line in above log indicates that the existing row was
+   modified by a local change, users can manually perform a remote-change-win
+   resolution by deleting the local row.
   </para>
 
   <para>
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..ad3eda1459 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,97 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * If no conflict is found, return false and set *conflictslot to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned in
+ * *conflictslot. The lock is essential to allow retrying to find the
+ * conflicting tuple in case the tuple is concurrently deleted.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Re-check all the unique indexes in 'recheckIndexes' to see if there are
+ * potential conflicts with the tuple in 'slot'.
+ *
+ * This function is invoked after inserting or updating a tuple that detected
+ * potential conflict tuples. It attempts to find the tuple that conflicts with
+ * the provided tuple. This operation may seem redundant with the unique
+ * violation check of indexam, but since we call this function only when we are
+ * detecting conflict in logical replication and encountering potential
+ * conflicts with any unique index constraints (which should not be frequent),
+ * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
+ * restart the logical replication, so the additional cost of finding the tuple
+ * should be acceptable.
+ */
+static void
+ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Re-check all the unique indexes for potential conflicts */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +594,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +612,28 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Rechecks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * perform an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +682,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +700,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to ReCheckConflictIndexes() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..287f62f3ba
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,247 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Build the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+				{
+					char	   *origin_name;
+
+					if (localorigin == InvalidRepOriginId)
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified locally in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+					else if (replorigin_by_oid(localorigin, true, &origin_name))
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin \"%s\" in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx), origin_name,
+										 localxmin, timestamptz_to_str(localts));
+
+					/*
+					 * The origin which modified the row has been dropped.
+					 * This situation may occur if the origin was created by a
+					 * different apply worker, but its associated subscription
+					 * and origin were dropped after updating the row, or if
+					 * the origin was manually dropped by the user.
+					 */
+					else
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by a non-existent origin in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+				}
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Updating a row that was modified locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Updating a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Updating a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Deleting a row that was modified by locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Deleting a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Deleting a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ec96b5fe85..0541e8a165 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,7 +2648,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2661,6 +2663,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 */
+		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2683,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2678,13 +2695,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2820,24 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 *
+		 * For cross-partition update, we skip detecting the delete_differ
+		 * conflict since it should have been done in
+		 * apply_handle_tuple_routing().
+		 */
+		if ((!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2849,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2991,6 +3018,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				ResultRelInfo *partrelinfo_new;
 				Relation	partrel_new;
 				bool		found;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3002,16 +3032,25 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										partrel, InvalidOid,
+										InvalidTransactionId,
+										InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * Check whether the local tuple was modified by a different
+				 * origin. If detected, report the conflict.
+				 */
+				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3039,7 +3078,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, false);
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..3d5383c056 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -636,6 +636,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..3a7260d3c1
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..79cbed2e5b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,12 +331,6 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -352,10 +346,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..896985d85b 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,30 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..ac7c8bbe7c 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict .* detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by .*origin.* transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..5a22413464 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict update_differ detected on relation "public.tab".*\n.*DETAIL:.* Updating a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict delete_differ detected on relation "public.tab".*\n.*DETAIL:.* Deleting a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 8de9978ad8..b0878d9ca8 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From d35f141d42ffb9e00eefd494bbb56de2b997c96d Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 11:18:49 +0800
Subject: [PATCH v9 2/3] Add a detect_conflict option to subscriptions

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will go
for confict detection and provide additional logging information. To avoid the
potential overhead introduced by conflict detection, detect_conflict will be
off for a subscription by default.
---
 doc/src/sgml/catalogs.sgml                 |   9 +
 doc/src/sgml/logical-replication.sgml      | 115 +++----------
 doc/src/sgml/ref/alter_subscription.sgml   |   5 +-
 doc/src/sgml/ref/create_subscription.sgml  |  89 ++++++++++
 src/backend/catalog/pg_subscription.c      |   1 +
 src/backend/catalog/system_views.sql       |   3 +-
 src/backend/commands/subscriptioncmds.c    |  54 +++++-
 src/backend/replication/logical/worker.c   |  58 ++++---
 src/bin/pg_dump/pg_dump.c                  |  17 +-
 src/bin/pg_dump/pg_dump.h                  |   1 +
 src/bin/psql/describe.c                    |   6 +-
 src/bin/psql/tab-complete.c                |  14 +-
 src/include/catalog/pg_subscription.h      |   4 +
 src/test/regress/expected/subscription.out | 188 ++++++++++++---------
 src/test/regress/sql/subscription.sql      |  19 +++
 src/test/subscription/t/001_rep_changes.pl |   7 +
 src/test/subscription/t/013_partition.pl   |  23 +++
 src/test/subscription/t/029_on_error.pl    |   2 +-
 src/test/subscription/t/030_origin.pl      |   7 +-
 19 files changed, 413 insertions(+), 209 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index c1f6f1aaa8..989e724602 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1580,87 +1580,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
-  </para>
-
-  <para>
-   Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   scenarios:
-   <variablelist>
-    <varlistentry>
-     <term><literal>insert_exists</literal></term>
-     <listitem>
-      <para>
-       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_exists</literal></term>
-     <listitem>
-      <para>
-       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually. Note that when updating a
-       partitioned table, if the updated row value satisfies another
-       partition constraint resulting in the row being inserted into a
-       new partition, the <literal>insert_exists</literal> conflict may
-       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_differ</literal></term>
-     <listitem>
-      <para>
-       Updating a row that was previously modified by another origin.
-       Note that this conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the update is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be updated was not found. The update will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_differ</literal></term>
-     <listitem>
-      <para>
-       Deleting a row that was previously modified by another origin. Note that this
-       conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the delete is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be deleted was not found. The delete will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-   </variablelist>
+   will simply be skipped. Please refer to
+   <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1689,8 +1611,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  conflict insert_exists detected on relation "public.test"
-DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+ERROR:  duplicate key value violates unique constraint "test_pkey"
+DETAIL:  Key (c)=(1) already exists.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1716,15 +1638,6 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
-   The additional details regarding conflicting rows, such as their origin and
-   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
-   log. But note that this information is only available when
-   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-   is enabled. Users can use these information to make decisions on whether to
-   retain the local change or adopt the remote alteration. For instance, the
-   <literal>DETAIL</literal> line in above log indicates that the existing row was
-   modified by a local change, users can manually perform a remote-change-win
-   resolution by deleting the local row.
   </para>
 
   <para>
@@ -1738,6 +1651,24 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.test" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   <literal>DETAIL</literal> line in above log indicates that the existing row was
+   modified by a local change, users can manually perform a remote-change-win
+   resolution by deleting the local row.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index fdc648d007..dfbe25b59e 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -235,8 +235,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
       <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>.
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>,
+      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..c406ae0fd6 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,95 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually. Note that when updating a
+              partitioned table, if the updated row value satisfies another
+              partition constraint resulting in the row being inserted into a
+              new partition, the <literal>insert_exists</literal> conflict may
+              arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the update is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the delete is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index d124bfe55c..a949d246df 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -14,6 +14,7 @@
 
 #include "postgres.h"
 
+#include "access/commit_ts.h"
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/twophase.h"
@@ -71,8 +72,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -98,6 +100,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -112,6 +115,7 @@ static List *merge_publications(List *oldpublist, List *newpublist, bool addpub,
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
 static void CheckAlterSubOption(Subscription *sub, const char *option,
 								bool slot_needs_update, bool isTopLevel);
+static void check_conflict_detection(void);
 
 
 /*
@@ -162,6 +166,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -307,6 +313,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -594,7 +609,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -639,6 +655,9 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 				 errmsg("password_required=false is superuser-only"),
 				 errhint("Subscriptions with the password_required option set to false may only be created or modified by the superuser.")));
 
+	if (opts.detectconflict)
+		check_conflict_detection();
+
 	/*
 	 * If built with appropriate switch, whine when regression-testing
 	 * conventions for subscription names are violated.
@@ -701,6 +720,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1196,7 +1217,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1356,6 +1377,16 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+
+					if (opts.detectconflict)
+						check_conflict_detection();
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
@@ -2536,3 +2567,18 @@ defGetStreamingMode(DefElem *def)
 					def->defname)));
 	return LOGICALREP_STREAM_OFF;	/* keep compiler quiet */
 }
+
+/*
+ * Report a warning about incomplete conflict detection if
+ * track_commit_timestamp is disabled.
+ */
+static void
+check_conflict_detection(void)
+{
+	if (!track_commit_timestamp)
+		ereport(WARNING,
+				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				errmsg("conflict detection could be incomplete due to disabled track_commit_timestamp"),
+				errdetail("Conflicts update_differ and delete_differ cannot be detected, "
+						  "and the origin and commit timestamp for the local row will not be logged."));
+}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 0541e8a165..6575b040a7 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2459,8 +2459,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, true);
-	InitConflictIndexes(relinfo);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2648,7 +2650,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, true);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2668,10 +2670,11 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 */
-		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2683,7 +2686,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
-		InitConflictIndexes(relinfo);
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
 
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
@@ -2696,8 +2700,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2825,14 +2830,15 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 *
 		 * For cross-partition update, we skip detecting the delete_differ
 		 * conflict since it should have been done in
 		 * apply_handle_tuple_routing().
 		 */
-		if ((!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
+		if (MySubscription->detectconflict &&
+			(!edata->mtstate || edata->mtstate->operation != CMD_UPDATE) &&
 			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
@@ -2850,8 +2856,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -3033,19 +3040,22 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
 					 */
-					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
-										partrel, InvalidOid,
-										InvalidTransactionId,
-										InvalidRepOriginId, 0, NULL);
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
 
 					return;
 				}
 
 				/*
-				 * Check whether the local tuple was modified by a different
-				 * origin. If detected, report the conflict.
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
 				 */
-				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)
 					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
 										InvalidOid, localxmin, localorigin,
@@ -3078,8 +3088,10 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					EPQState	epqstate;
 
 					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-					ExecOpenIndices(partrelinfo, true);
-					InitConflictIndexes(partrelinfo);
+					ExecOpenIndices(partrelinfo, MySubscription->detectconflict);
+
+					if (MySubscription->detectconflict)
+						InitConflictIndexes(partrelinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 0d02516273..460478a51c 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4800,6 +4800,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4872,11 +4873,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4915,6 +4922,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4961,6 +4969,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5201,6 +5211,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 024469474d..1c416cf527 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3357,9 +3358,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 17d48b1685..118f207df5 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,19 +371,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- we can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -393,10 +393,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -409,18 +409,54 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 007c9e7037..b3f2ab1684 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -287,6 +287,25 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 79cbed2e5b..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,6 +331,13 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
+
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 896985d85b..a3effed937 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,6 +343,13 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
+
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -377,6 +384,10 @@ ok( $logfile =~
 	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
+
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -762,6 +773,13 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
+
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -800,6 +818,11 @@ ok( $logfile =~
 	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
 	'updating a tuple that was modified by a different origin');
 
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
 $node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_subscriber1->restart;
 
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index ac7c8bbe7c..b71d0c3400 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -111,7 +111,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 5a22413464..6bc4474d15 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -149,7 +149,9 @@ is($result, qq(),
 # delete a row that was previously modified by a different source.
 ###############################################################################
 
-$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
 
 $node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
 
@@ -183,6 +185,9 @@ $node_B->wait_for_log(
 );
 
 # The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
 $node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_B->restart;
 
-- 
2.30.0.windows.2

From db6a0c5b68bb62d4e6e69b2c4abb5b9de2a4b363 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Wed, 3 Jul 2024 10:34:10 +0800
Subject: [PATCH v10 3/3] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  80 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  33 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 125 +++++++++++++++++-
 11 files changed, 274 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..7b93334967 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,84 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index c406ae0fd6..681d94d38d 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected (displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..5244d8e356 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_exists_count,
+        ss.update_differ_count,
+        ss.update_missing_count,
+        ss.delete_missing_count,
+        ss.delete_differ_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 287f62f3ba..b9a7120d0e 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -80,6 +82,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e36ddb4cac 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 54b50ee5d6..edf4cc6486 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5538,9 +5538,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_exists_count,update_differ_count,update_missing_count,delete_missing_count,delete_differ_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 6b99bb8aad..ad6619bcd0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -14,6 +14,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 3a7260d3c1..b5e9c79100 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -39,6 +44,8 @@ typedef enum
 	CT_DELETE_DIFFER,
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_DIFFER + 1)
+
 extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
 							 RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 5201280669..3c1154b14b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2140,9 +2140,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_exists_count,
+    ss.update_differ_count,
+    ss.update_missing_count,
+    ss.delete_missing_count,
+    ss.delete_differ_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_exists_count, update_differ_count, update_missing_count, delete_missing_count, delete_differ_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..56eafa5ba6 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +233,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +279,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_exists_count > 0,
+	update_differ_count > 0,
+	update_missing_count > 0,
+	delete_missing_count > 0,
+	delete_differ_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +302,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +320,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_exists_count = 0,
+	update_differ_count = 0,
+	update_missing_count = 0,
+	delete_missing_count = 0,
+	delete_differ_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From b67cfe0307d9f32fa577e0e594224bb8ad912670 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v10 1/3] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_missing: The tuple to be updated is missing.
delete_missing: The tuple to be deleted is missing.
delete_differ: Deleting a row that was previously modified by another origin.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.
---
 doc/src/sgml/logical-replication.sgml       |  93 +++++++-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execReplication.c      | 239 ++++++++++++++-----
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 247 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  80 +++++--
 src/include/executor/executor.h             |   1 +
 src/include/replication/conflict.h          |  50 ++++
 src/test/subscription/t/001_rep_changes.pl  |  10 +-
 src/test/subscription/t/013_partition.pl    |  51 ++--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++++
 src/tools/pgindent/typedefs.list            |   1 +
 16 files changed, 728 insertions(+), 131 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..c1f6f1aaa8 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1583,6 +1583,86 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    will simply be skipped.
   </para>
 
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   scenarios:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to obtain the origin and commit
+       timestamp details of the conflicting key in the log, ensure that
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. In this scenario, an error will be raised until the
+       conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another
+       partition constraint resulting in the row being inserted into a
+       new partition, the <literal>insert_exists</literal> conflict may
+       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the update is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that this
+       conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled. Currenly, the delete is always applied regardless of
+       the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+  </para>
+
   <para>
    Logical replication operations are performed with the privileges of the role
    which owns the subscription.  Permissions failures on target tables will
@@ -1609,8 +1689,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1716,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled. Users can use these information to make decisions on whether to
+   retain the local change or adopt the remote alteration. For instance, the
+   <literal>DETAIL</literal> line in above log indicates that the existing row was
+   modified by a local change, users can manually perform a remote-change-win
+   resolution by deleting the local row.
   </para>
 
   <para>
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..ad3eda1459 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,97 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed in unique index constraint
+ * (conflictindex).
+ *
+ * If no conflict is found, return false and set *conflictslot to NULL.
+ * Otherwise return true, and the conflicting tuple is locked and returned in
+ * *conflictslot. The lock is essential to allow retrying to find the
+ * conflicting tuple in case the tuple is concurrently deleted.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Re-check all the unique indexes in 'recheckIndexes' to see if there are
+ * potential conflicts with the tuple in 'slot'.
+ *
+ * This function is invoked after inserting or updating a tuple that detected
+ * potential conflict tuples. It attempts to find the tuple that conflicts with
+ * the provided tuple. This operation may seem redundant with the unique
+ * violation check of indexam, but since we call this function only when we are
+ * detecting conflict in logical replication and encountering potential
+ * conflicts with any unique index constraints (which should not be frequent),
+ * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
+ * restart the logical replication, so the additional cost of finding the tuple
+ * should be acceptable.
+ */
+static void
+ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Re-check all the unique indexes for potential conflicts */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleCommitTs(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +594,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +612,28 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Rechecks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * perform an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +682,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +700,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to ReCheckConflictIndexes() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..287f62f3ba
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,247 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_MISSING] = "delete_missing",
+	[CT_DELETE_DIFFER] = "delete_differ"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+				 RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Build the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+				{
+					char	   *origin_name;
+
+					if (localorigin == InvalidRepOriginId)
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified locally in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+					else if (replorigin_by_oid(localorigin, true, &origin_name))
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin \"%s\" in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx), origin_name,
+										 localxmin, timestamptz_to_str(localts));
+
+					/*
+					 * The origin which modified the row has been dropped.
+					 * This situation may occur if the origin was created by a
+					 * different apply worker, but its associated subscription
+					 * and origin were dropped after updating the row, or if
+					 * the origin was manually dropped by the user.
+					 */
+					else
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by a non-existent origin in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+				}
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Updating a row that was modified locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Updating a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Updating a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+		case CT_DELETE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Deleting a row that was modified by locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Deleting a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Deleting a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6dc54c7283..b1dc04ec7e 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,7 +2648,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2661,6 +2663,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 */
+		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2683,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2678,13 +2695,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2820,19 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Check whether the local tuple was modified by a different origin.
+		 * If detected, report the conflict.
+		 */
+		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2844,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2992,6 +3014,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3003,16 +3028,25 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										partrel, InvalidOid,
+										InvalidTransactionId,
+										InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * Check whether the local tuple was modified by a different
+				 * origin. If detected, report the conflict.
+				 */
+				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3023,7 +3057,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3040,6 +3073,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3087,6 +3123,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..3d5383c056 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -636,6 +636,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..3a7260d3c1
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2012-2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+} ConflictType;
+
+extern bool GetTupleCommitTs(TupleTableSlot *localslot, TransactionId *xmin,
+							 RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..79cbed2e5b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,12 +331,6 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -352,10 +346,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..896985d85b 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,30 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..ac7c8bbe7c 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict .* detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by .*origin.* transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..5a22413464 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict update_differ detected on relation "public.tab".*\n.*DETAIL:.* Updating a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict delete_differ detected on relation "public.tab".*\n.*DETAIL:.* Deleting a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 8de9978ad8..b0878d9ca8 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 49be09cb9e85819483a21b9555320e01229e376e Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:52:17 +0800
Subject: [PATCH v10 2/3] Add a detect_conflict option to subscriptions

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will go
for confict detection and provide additional logging information. To avoid the
potential overhead introduced by conflict detection, detect_conflict will be
off for a subscription by default.
---
 doc/src/sgml/catalogs.sgml                 |   9 +
 doc/src/sgml/logical-replication.sgml      | 115 +++----------
 doc/src/sgml/ref/alter_subscription.sgml   |   5 +-
 doc/src/sgml/ref/create_subscription.sgml  |  89 ++++++++++
 src/backend/catalog/pg_subscription.c      |   1 +
 src/backend/catalog/system_views.sql       |   3 +-
 src/backend/commands/subscriptioncmds.c    |  54 +++++-
 src/backend/replication/logical/worker.c   |  58 ++++---
 src/bin/pg_dump/pg_dump.c                  |  17 +-
 src/bin/pg_dump/pg_dump.h                  |   1 +
 src/bin/psql/describe.c                    |   6 +-
 src/bin/psql/tab-complete.c                |  14 +-
 src/include/catalog/pg_subscription.h      |   4 +
 src/test/regress/expected/subscription.out | 188 ++++++++++++---------
 src/test/regress/sql/subscription.sql      |  19 +++
 src/test/subscription/t/001_rep_changes.pl |   7 +
 src/test/subscription/t/013_partition.pl   |  23 +++
 src/test/subscription/t/029_on_error.pl    |   2 +-
 src/test/subscription/t/030_origin.pl      |   7 +-
 19 files changed, 413 insertions(+), 209 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index c1f6f1aaa8..989e724602 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1580,87 +1580,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
-  </para>
-
-  <para>
-   Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   scenarios:
-   <variablelist>
-    <varlistentry>
-     <term><literal>insert_exists</literal></term>
-     <listitem>
-      <para>
-       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_exists</literal></term>
-     <listitem>
-      <para>
-       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
-       conflict is resolved manually. Note that when updating a
-       partitioned table, if the updated row value satisfies another
-       partition constraint resulting in the row being inserted into a
-       new partition, the <literal>insert_exists</literal> conflict may
-       arise if the new row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_differ</literal></term>
-     <listitem>
-      <para>
-       Updating a row that was previously modified by another origin.
-       Note that this conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the update is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be updated was not found. The update will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_differ</literal></term>
-     <listitem>
-      <para>
-       Deleting a row that was previously modified by another origin. Note that this
-       conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. Currenly, the delete is always applied regardless of
-       the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be deleted was not found. The delete will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-   </variablelist>
+   will simply be skipped. Please refer to
+   <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1689,8 +1611,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  conflict insert_exists detected on relation "public.test"
-DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+ERROR:  duplicate key value violates unique constraint "test_pkey"
+DETAIL:  Key (c)=(1) already exists.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1716,15 +1638,6 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
-   The additional details regarding conflicting rows, such as their origin and
-   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
-   log. But note that this information is only available when
-   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-   is enabled. Users can use these information to make decisions on whether to
-   retain the local change or adopt the remote alteration. For instance, the
-   <literal>DETAIL</literal> line in above log indicates that the existing row was
-   modified by a local change, users can manually perform a remote-change-win
-   resolution by deleting the local row.
   </para>
 
   <para>
@@ -1738,6 +1651,24 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.test" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use these information to make decisions on whether to retain
+   the local change or adopt the remote alteration. For instance, the
+   <literal>DETAIL</literal> line in above log indicates that the existing row was
+   modified by a local change, users can manually perform a remote-change-win
+   resolution by deleting the local row.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index fdc648d007..dfbe25b59e 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -235,8 +235,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
       <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>.
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>,
+      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..c406ae0fd6 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,95 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to obtain the origin and commit
+              timestamp details of the conflicting key in the log, ensure that
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. In this scenario, an error will be raised until the
+              conflict is resolved manually. Note that when updating a
+              partitioned table, if the updated row value satisfies another
+              partition constraint resulting in the row being inserted into a
+              new partition, the <literal>insert_exists</literal> conflict may
+              arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the update is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin. Note that this
+              conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled. Currenly, the delete is always applied regardless of
+              the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index d124bfe55c..a949d246df 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -14,6 +14,7 @@
 
 #include "postgres.h"
 
+#include "access/commit_ts.h"
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/twophase.h"
@@ -71,8 +72,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -98,6 +100,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -112,6 +115,7 @@ static List *merge_publications(List *oldpublist, List *newpublist, bool addpub,
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
 static void CheckAlterSubOption(Subscription *sub, const char *option,
 								bool slot_needs_update, bool isTopLevel);
+static void check_conflict_detection(void);
 
 
 /*
@@ -162,6 +166,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -307,6 +313,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -594,7 +609,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -639,6 +655,9 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 				 errmsg("password_required=false is superuser-only"),
 				 errhint("Subscriptions with the password_required option set to false may only be created or modified by the superuser.")));
 
+	if (opts.detectconflict)
+		check_conflict_detection();
+
 	/*
 	 * If built with appropriate switch, whine when regression-testing
 	 * conventions for subscription names are violated.
@@ -701,6 +720,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1196,7 +1217,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1356,6 +1377,16 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+
+					if (opts.detectconflict)
+						check_conflict_detection();
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
@@ -2536,3 +2567,18 @@ defGetStreamingMode(DefElem *def)
 					def->defname)));
 	return LOGICALREP_STREAM_OFF;	/* keep compiler quiet */
 }
+
+/*
+ * Report a warning about incomplete conflict detection if
+ * track_commit_timestamp is disabled.
+ */
+static void
+check_conflict_detection(void)
+{
+	if (!track_commit_timestamp)
+		ereport(WARNING,
+				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				errmsg("conflict detection could be incomplete due to disabled track_commit_timestamp"),
+				errdetail("Conflicts update_differ and delete_differ cannot be detected, "
+						  "and the origin and commit timestamp for the local row will not be logged."));
+}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b1dc04ec7e..a22fb883a0 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2459,8 +2459,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, true);
-	InitConflictIndexes(relinfo);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2648,7 +2650,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, true);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2668,10 +2670,11 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 */
-		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2683,7 +2686,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
-		InitConflictIndexes(relinfo);
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
 
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
@@ -2696,8 +2700,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2825,10 +2830,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * If conflict detection is enabled, check whether the local tuple was
+		 * modified by a different origin. If detected, report the conflict.
 		 */
-		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2845,8 +2851,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -3029,19 +3036,22 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
 					 */
-					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
-										partrel, InvalidOid,
-										InvalidTransactionId,
-										InvalidRepOriginId, 0, NULL);
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
 
 					return;
 				}
 
 				/*
-				 * Check whether the local tuple was modified by a different
-				 * origin. If detected, report the conflict.
+				 * If conflict detection is enabled, check whether the local
+				 * tuple was modified by a different origin. If detected,
+				 * report the conflict.
 				 */
-				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
+				if (MySubscription->detectconflict &&
+					GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)
 					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
 										InvalidOid, localxmin, localorigin,
@@ -3073,8 +3083,10 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
-					ExecOpenIndices(partrelinfo, true);
-					InitConflictIndexes(partrelinfo);
+					ExecOpenIndices(partrelinfo, MySubscription->detectconflict);
+
+					if (MySubscription->detectconflict)
+						InitConflictIndexes(partrelinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 0d02516273..460478a51c 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4800,6 +4800,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4872,11 +4873,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4915,6 +4922,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4961,6 +4969,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5201,6 +5211,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 024469474d..1c416cf527 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3357,9 +3358,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 17d48b1685..118f207df5 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,19 +371,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- we can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -393,10 +393,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -409,18 +409,54 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 007c9e7037..b3f2ab1684 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -287,6 +287,25 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 79cbed2e5b..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,6 +331,13 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
+
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 896985d85b..a3effed937 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,6 +343,13 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
+
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -377,6 +384,10 @@ ok( $logfile =~
 	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
+
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -762,6 +773,13 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
+
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -800,6 +818,11 @@ ok( $logfile =~
 	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
 	'updating a tuple that was modified by a different origin');
 
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
 $node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_subscriber1->restart;
 
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index ac7c8bbe7c..b71d0c3400 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -111,7 +111,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 5a22413464..6bc4474d15 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -149,7 +149,9 @@ is($result, qq(),
 # delete a row that was previously modified by a different source.
 ###############################################################################
 
-$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
 
 $node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
 
@@ -183,6 +185,9 @@ $node_B->wait_for_log(
 );
 
 # The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
 $node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_B->restart;
 
-- 
2.30.0.windows.2

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index c1f6f1aaa8..dfbff3de02 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1585,17 +1585,17 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
 
   <para>
    Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   scenarios:
+   cases:
    <variablelist>
     <varlistentry>
      <term><literal>insert_exists</literal></term>
      <listitem>
       <para>
        Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
        <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
+       should be enabled. In this case, an error will be raised until the
        conflict is resolved manually.
       </para>
      </listitem>
@@ -1605,10 +1605,10 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
      <listitem>
       <para>
        The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to obtain the origin and commit
-       timestamp details of the conflicting key in the log, ensure that
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
        <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled. In this scenario, an error will be raised until the
+       is enabled. In this case, an error will be raised until the
        conflict is resolved manually. Note that when updating a
        partitioned table, if the updated row value satisfies another
        partition constraint resulting in the row being inserted into a
@@ -1720,10 +1720,10 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    commit timestamp can be seen in the <literal>DETAIL</literal> line of the
    log. But note that this information is only available when
    <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-   is enabled. Users can use these information to make decisions on whether to
-   retain the local change or adopt the remote alteration. For instance, the
-   <literal>DETAIL</literal> line in above log indicates that the existing row was
-   modified by a local change, users can manually perform a remote-change-win
+   is enabled. Users can use this information to decide whether to retain the
+   local change or adopt the remote alteration. For instance, the
+   <literal>DETAIL</literal> line in the above log indicates that the existing
+   row was modified locally. Users can manually perform a remote-change-win
    resolution by deleting the local row.
   </para>
 
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index ad3eda1459..34050a3bae 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -475,13 +475,13 @@ retry:
 }
 
 /*
- * Find the tuple that violates the passed in unique index constraint
- * (conflictindex).
+ * Find the tuple that violates the passed unique index (conflictindex).
  *
- * If no conflict is found, return false and set *conflictslot to NULL.
- * Otherwise return true, and the conflicting tuple is locked and returned in
- * *conflictslot. The lock is essential to allow retrying to find the
- * conflicting tuple in case the tuple is concurrently deleted.
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
  */
 static bool
 FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
@@ -528,25 +528,15 @@ retry:
 }
 
 /*
- * Re-check all the unique indexes in 'recheckIndexes' to see if there are
- * potential conflicts with the tuple in 'slot'.
- *
- * This function is invoked after inserting or updating a tuple that detected
- * potential conflict tuples. It attempts to find the tuple that conflicts with
- * the provided tuple. This operation may seem redundant with the unique
- * violation check of indexam, but since we call this function only when we are
- * detecting conflict in logical replication and encountering potential
- * conflicts with any unique index constraints (which should not be frequent),
- * so it's ok. Moreover, upon detecting a conflict, we will report an ERROR and
- * restart the logical replication, so the additional cost of finding the tuple
- * should be acceptable.
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
  */
 static void
-ReCheckConflictIndexes(ResultRelInfo *resultRelInfo, EState *estate,
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
 					   ConflictType type, List *recheckIndexes,
 					   TupleTableSlot *slot)
 {
-	/* Re-check all the unique indexes for potential conflicts */
+	/* Check all the unique indexes for a conflict */
 	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
 	{
 		TupleTableSlot *conflictslot;
@@ -622,17 +612,22 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 												   conflictindexes, false);
 
 		/*
-		 * Rechecks the conflict indexes to fetch the conflicting local tuple
+		 * Checks the conflict indexes to fetch the conflicting local tuple
 		 * and reports the conflict. We perform this check here, instead of
-		 * perform an additional index scan before the actual insertion and
+		 * performing an additional index scan before the actual insertion and
 		 * reporting the conflict if any conflicting tuples are found. This is
 		 * to avoid the overhead of executing the extra scan for each INSERT
 		 * operation, even when no conflict arises, which could introduce
 		 * significant overhead to replication, particularly in cases where
 		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance overhead
+		 * of extra scan before each insertion.
 		 */
 		if (conflict)
-			ReCheckConflictIndexes(resultRelInfo, estate, CT_INSERT_EXISTS,
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
 								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
@@ -710,12 +705,12 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 												   (update_indexes == TU_Summarizing));
 
 		/*
-		 * Refer to the comments above the call to ReCheckConflictIndexes() in
+		 * Refer to the comments above the call to CheckAndReportConflict() in
 		 * ExecSimpleRelationInsert to understand why this check is done at
 		 * this point.
 		 */
 		if (conflict)
-			ReCheckConflictIndexes(resultRelInfo, estate, CT_UPDATE_EXISTS,
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
 								   recheckIndexes, slot);
 
 		/* AFTER ROW UPDATE Triggers */
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b1dc04ec7e..bff98a236d 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2668,8 +2668,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * Report the conflict if the tuple was modified by a different origin.
 		 */
 		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
@@ -2825,8 +2824,7 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Check whether the local tuple was modified by a different origin.
-		 * If detected, report the conflict.
+		 * Report the conflict if the tuple was modified by a different origin.
 		 */
 		if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
@@ -3038,8 +3036,7 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				}
 
 				/*
-				 * Check whether the local tuple was modified by a different
-				 * origin. If detected, report the conflict.
+				 * Report the conflict if the tuple was modified by a different origin.
 				 */
 				if (GetTupleCommitTs(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)

From 45f2cf19fc7b66f2301c3e20f4b02a4ddc124cf1 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Sun, 4 Aug 2024 15:43:18 +0800
Subject: [PATCH v11 3/3] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.

The conflicts will be tracked only when detect_conflict option of the
subscription is enabled. Additionally, update_differ and delete_differ
can be detected only when track_commit_timestamp is enabled.
---
 doc/src/sgml/monitoring.sgml                  |  80 ++++++++++-
 doc/src/sgml/ref/create_subscription.sgml     |   5 +-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   4 +
 .../utils/activity/pgstat_subscription.c      |  17 +++
 src/backend/utils/adt/pgstatfuncs.c           |  33 ++++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 125 +++++++++++++++++-
 11 files changed, 274 insertions(+), 21 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..3bdc1334d2 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,84 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       option of the subscription and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       are enabled
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes. This conflict is counted only if
+       <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+       is enabled
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 067131337f..2f7689cebc 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -437,8 +437,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           The default is <literal>false</literal>.
          </para>
          <para>
-          When conflict detection is enabled, additional logging is triggered
-          in the following scenarios:
+          When conflict detection is enabled, additional logging is triggered and
+          the conflict statistics are collected (displayed in the
+          <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view) in the following scenarios:
           <variablelist>
            <varlistentry>
             <term><literal>insert_exists</literal></term>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index d084bfc48a..a42977373f 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1366,6 +1366,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_differ_count,
+        ss.update_exists_count,
+        ss.update_missing_count,
+        ss.delete_differ_count,
+        ss.delete_missing_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index c69194244c..e286ee7dc1 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -15,8 +15,10 @@
 #include "postgres.h"
 
 #include "access/commit_ts.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
 #include "replication/origin.h"
+#include "replication/worker_internal.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
@@ -80,6 +82,8 @@ ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
 					RepOriginId localorigin, TimestampTz localts,
 					TupleTableSlot *conflictslot)
 {
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
 			errmsg("conflict %s detected on relation \"%s.%s\"",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3876339ee1..e1bd4157d1 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index d36f6001bb..1a7930e1c9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5538,9 +5538,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_differ_count,update_exists_count,update_missing_count,delete_differ_count,delete_missing_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index f84e9fdeca..0677e7a684 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -15,6 +15,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -135,6 +136,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -393,6 +395,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -695,6 +698,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 631be03574..0cdf16c88f 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -17,6 +17,11 @@
 
 /*
  * Conflict types that could be encountered when applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -45,6 +50,8 @@ typedef enum
 	 */
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_MISSING + 1)
+
 extern bool GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
 									RepOriginId *localorigin, TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 5201280669..f38cf0be34 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2140,9 +2140,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_differ_count,
+    ss.update_exists_count,
+    ss.update_missing_count,
+    ss.delete_differ_count,
+    ss.delete_missing_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_differ_count, update_exists_count, update_missing_count, delete_differ_count, delete_missing_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..997e1f8da1 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,7 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+$node_subscriber->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_subscriber->start;
 
 
@@ -30,6 +31,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -53,7 +55,7 @@ sub create_sub_pub_w_errors
 	# infinite error loop due to violating the unique constraint.
 	my $sub_name = $table_name . '_sub';
 	$node_subscriber->safe_psql($db,
-		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name)
+		qq(CREATE SUBSCRIPTION $sub_name CONNECTION '$publisher_connstr' PUBLICATION $pub_name WITH (detect_conflict = on))
 	);
 
 	$node_publisher->wait_for_catchup($sub_name);
@@ -95,7 +97,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +107,85 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+	# Update data from test table on the publisher, raising an error on the
+	# subscriber due to violation of the unique constraint on test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the apply error to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table so that the update will be skipped and the test can
+	# continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# delete the data from test table on the publisher. The delete should be
+	# skipped on the subscriber as there are no data in the test table.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the tuple missing to be reported.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update data from test table on the publisher, updating a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data to test table on the publisher, deleting a row on the
+	# subscriber that was modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,11 +209,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_exists_count > 0,
+	update_missing_count > 0,
+	delete_differ_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
@@ -146,11 +233,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_exists_count = 0,
+	update_missing_count = 0,
+	delete_differ_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
@@ -186,11 +279,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_exists_count > 0,
+	update_missing_count > 0,
+	delete_differ_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
@@ -203,11 +302,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_exists_count = 0,
+	update_missing_count = 0,
+	delete_differ_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
@@ -215,11 +320,17 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_exists_count = 0,
+	update_missing_count = 0,
+	delete_differ_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
+	qq(t|t|t|t|t|t|t|t|t),
 	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
-- 
2.30.0.windows.2

From cd587f611d67cdc503870b7695b44dc7fa5166c5 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v11 1/3] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       |  95 +++++++-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execReplication.c      | 234 ++++++++++++++-----
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 246 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    |  77 ++++--
 src/include/executor/executor.h             |   1 +
 src/include/replication/conflict.h          |  56 +++++
 src/test/subscription/t/001_rep_changes.pl  |  10 +-
 src/test/subscription/t/013_partition.pl    |  51 ++--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++++
 src/tools/pgindent/typedefs.list            |   1 +
 16 files changed, 727 insertions(+), 131 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..57216d6c52 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1583,6 +1583,88 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    will simply be skipped.
   </para>
 
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled. In this case, an error will be raised until the
+       conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
+  </para>
+
   <para>
    Logical replication operations are performed with the privileges of the role
    which owns the subscription.  Permissions failures on target tables will
@@ -1609,8 +1691,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1718,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..09b51706db 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,87 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
+								xmin, origin, committs, conflictslot);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +584,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +602,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance overhead
+		 * of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +677,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +695,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..c69194244c
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,246 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "replication/conflict.h"
+#include "replication/origin.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+
+const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static char *build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot);
+static int	errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+									 TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *conflictslot);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, Relation localrel,
+					Oid conflictidx, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *conflictslot)
+{
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict %s detected on relation \"%s.%s\"",
+				   ConflictTypeNames[type],
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel)),
+			errdetail_apply_conflict(type, conflictidx, localxmin, localorigin,
+									 localts, conflictslot));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, Oid conflictidx,
+						 TransactionId localxmin, RepOriginId localorigin,
+						 TimestampTz localts, TupleTableSlot *conflictslot)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			{
+				/*
+				 * Build the index value string. If the return value is NULL,
+				 * it indicates that the current user lacks permissions to
+				 * view all the columns involved.
+				 */
+				char	   *index_value = build_index_value_desc(conflictidx,
+																 conflictslot);
+
+				if (index_value && localts)
+				{
+					char	   *origin_name;
+
+					if (localorigin == InvalidRepOriginId)
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified locally in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+					else if (replorigin_by_oid(localorigin, true, &origin_name))
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by origin \"%s\" in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx), origin_name,
+										 localxmin, timestamptz_to_str(localts));
+
+					/*
+					 * The origin which modified the row has been dropped.
+					 * This situation may occur if the origin was created by a
+					 * different apply worker, but its associated subscription
+					 * and origin were dropped after updating the row, or if
+					 * the origin was manually dropped by the user.
+					 */
+					else
+						return errdetail("Key %s already exists in unique index \"%s\", which was modified by a non-existent origin in transaction %u at %s.",
+										 index_value, get_rel_name(conflictidx),
+										 localxmin, timestamptz_to_str(localts));
+				}
+				else if (index_value && !localts)
+					return errdetail("Key %s already exists in unique index \"%s\", which was modified in transaction %u.",
+									 index_value, get_rel_name(conflictidx), localxmin);
+				else
+					return errdetail("Key already exists in unique index \"%s\".",
+									 get_rel_name(conflictidx));
+			}
+		case CT_UPDATE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Updating a row that was modified locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Updating a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Updating a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+
+		case CT_UPDATE_MISSING:
+			return errdetail("Did not find the row to be updated.");
+		case CT_DELETE_DIFFER:
+			{
+				char	   *origin_name;
+
+				if (localorigin == InvalidRepOriginId)
+					return errdetail("Deleting a row that was modified by locally in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					return errdetail("Deleting a row that was modified by a different origin \"%s\" in transaction %u at %s.",
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					return errdetail("Deleting a row that was modified by a non-existent origin in transaction %u at %s.",
+									 localxmin, timestamptz_to_str(localts));
+			}
+		case CT_DELETE_MISSING:
+			return errdetail("Did not find the row to be deleted.");
+	}
+
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'conflictidx' is
+ * locked.
+ */
+static char *
+build_index_value_desc(Oid indexoid, TupleTableSlot *conflictslot)
+{
+	char	   *conflict_row;
+	Relation	indexDesc;
+
+	if (!conflictslot)
+		return NULL;
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	slot_getallattrs(conflictslot);
+
+	conflict_row = BuildIndexValueDescription(indexDesc,
+											  conflictslot->tts_values,
+											  conflictslot->tts_isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return conflict_row;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6dc54c7283..b09d780fc5 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,7 +2648,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2661,6 +2663,18 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2682,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2678,13 +2694,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2819,18 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
+								localxmin, localorigin, localts, NULL);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2842,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2992,6 +3012,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3003,16 +3026,24 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										partrel, InvalidOid,
+										InvalidTransactionId,
+										InvalidRepOriginId, 0, NULL);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
+										InvalidOid, localxmin, localorigin,
+										localts, NULL);
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3023,7 +3054,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3040,6 +3070,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3087,6 +3120,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..3d5383c056 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -636,6 +636,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..631be03574
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,56 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "access/xlogdefs.h"
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+#include "utils/relcache.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve rules
+	 * that are more complex than simple equality checks. These conflicts are
+	 * left for future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+									RepOriginId *localorigin, TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								Relation localrel, Oid conflictidx,
+								TransactionId localxmin, RepOriginId localorigin,
+								TimestampTz localts, TupleTableSlot *conflictslot);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..79cbed2e5b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,12 +331,6 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -352,10 +346,10 @@ $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict update_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be updated./m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict delete_missing detected on relation "public.tab_full_pk".*\n.*DETAIL:.* Did not find the row to be deleted./m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..896985d85b 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict update_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_2_2".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,30 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict update_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be updated./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict delete_missing detected on relation "public.tab2_1".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab2_1');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
+	'updating a tuple that was modified by a different origin');
+
+$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..ac7c8bbe7c 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict .* detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by .*origin.* transaction \d+ at .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..5a22413464 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict update_differ detected on relation "public.tab".*\n.*DETAIL:.* Updating a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict delete_differ detected on relation "public.tab".*\n.*DETAIL:.* Deleting a row that was modified by a different origin ".*" in transaction [0-9]+ at .*/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 75fc05093c..df8661485b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From d6efc3526d143bf223edda0305b79f0342d7a3c1 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Sun, 4 Aug 2024 15:22:18 +0800
Subject: [PATCH v11 2/3] Add a detect_conflict option to subscriptions

This patch adds a new parameter detect_conflict for CREATE and ALTER
subscription commands. This new parameter will decide if subscription will go
for confict detection and provide additional logging information. To avoid the
potential overhead introduced by conflict detection, detect_conflict will be
off for a subscription by default.
---
 doc/src/sgml/catalogs.sgml                 |   9 +
 doc/src/sgml/logical-replication.sgml      | 116 +++----------
 doc/src/sgml/ref/alter_subscription.sgml   |   5 +-
 doc/src/sgml/ref/create_subscription.sgml  |  92 ++++++++++
 src/backend/catalog/pg_subscription.c      |   1 +
 src/backend/catalog/system_views.sql       |   3 +-
 src/backend/commands/subscriptioncmds.c    |  54 +++++-
 src/backend/replication/logical/worker.c   |  54 +++---
 src/bin/pg_dump/pg_dump.c                  |  17 +-
 src/bin/pg_dump/pg_dump.h                  |   1 +
 src/bin/psql/describe.c                    |   6 +-
 src/bin/psql/tab-complete.c                |  14 +-
 src/include/catalog/pg_subscription.h      |   4 +
 src/test/regress/expected/subscription.out | 188 ++++++++++++---------
 src/test/regress/sql/subscription.sql      |  19 +++
 src/test/subscription/t/001_rep_changes.pl |   7 +
 src/test/subscription/t/013_partition.pl   |  23 +++
 src/test/subscription/t/029_on_error.pl    |   2 +-
 src/test/subscription/t/030_origin.pl      |   7 +-
 19 files changed, 414 insertions(+), 208 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b654fae1b2..b042a5a94a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8035,6 +8035,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subdetectconflict</structfield> <type>bool</type>
+      </para>
+      <para>
+       If true, the subscription is enabled for conflict detection.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 57216d6c52..7d62774b06 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1580,89 +1580,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
    operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
-  </para>
-
-  <para>
-   Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   cases:
-   <variablelist>
-    <varlistentry>
-     <term><literal>insert_exists</literal></term>
-     <listitem>
-      <para>
-       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to log the origin and commit
-       timestamp details of the conflicting key,
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       should be enabled. In this case, an error will be raised until the
-       conflict is resolved manually.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_differ</literal></term>
-     <listitem>
-      <para>
-       Updating a row that was previously modified by another origin.
-       Note that this conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled on the subscriber. Currenly, the update is always applied
-       regardless of the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_exists</literal></term>
-     <listitem>
-      <para>
-       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
-       unique constraint. Note that to log the origin and commit
-       timestamp details of the conflicting key,
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       should be enabled on the subscriber. In this case, an error will be
-       raised until the conflict is resolved manually. Note that when updating a
-       partitioned table, if the updated row value satisfies another partition
-       constraint resulting in the row being inserted into a new partition, the
-       <literal>insert_exists</literal> conflict may arise if the new row
-       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>update_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be updated was not found. The update will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_differ</literal></term>
-     <listitem>
-      <para>
-       Deleting a row that was previously modified by another origin. Note that
-       this conflict can only be detected when
-       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       is enabled on the subscriber. Currenly, the delete is always applied
-       regardless of the origin of the local row.
-      </para>
-     </listitem>
-    </varlistentry>
-    <varlistentry>
-     <term><literal>delete_missing</literal></term>
-     <listitem>
-      <para>
-       The tuple to be deleted was not found. The delete will simply be
-       skipped in this scenario.
-      </para>
-     </listitem>
-    </varlistentry>
-   </variablelist>
-    Note that there are other conflict scenarios, such as exclusion constraint
-    violations. Currently, we do not provide additional details for them in the
-    log.
+   will simply be skipped. Please refer to
+   <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   for all the conflicts that will be logged when enabling <literal>detect_conflict</literal>.
   </para>
 
   <para>
@@ -1691,8 +1611,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  conflict insert_exists detected on relation "public.test"
-DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+ERROR:  duplicate key value violates unique constraint "test_pkey"
+DETAIL:  Key (c)=(1) already exists.
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1718,15 +1638,6 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
-   The additional details regarding conflicting rows, such as their origin and
-   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
-   log. But note that this information is only available when
-   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-   is enabled on the subscriber. Users can use this information to decide
-   whether to retain the local change or adopt the remote alteration. For
-   instance, the <literal>DETAIL</literal> line in the above log indicates that
-   the existing row was modified locally. Users can manually perform a
-   remote-change-win.
   </para>
 
   <para>
@@ -1740,6 +1651,23 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
    SKIP</command></link>.
   </para>
+
+  <para>
+   Enabling both <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>
+   and <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   on the subscriber can provide additional details regarding conflicting
+   rows, such as their origin and commit timestamp, in case of a unique
+   constraint violation conflict:
+<screen>
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+CONTEXT:  processing remote data for replication origin "pg_16389" during message type "INSERT" for replication target relation "public.test" in transaction 740, finished at 0/14F7EC0
+</screen>
+   Users can use this information to decide whether to retain the local change
+   or adopt the remote alteration. For instance, the <literal>DETAIL</literal>
+   line in the above log indicates that the existing row was modified locally.
+   Users can manually perform a remote-change-win.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index fdc648d007..dfbe25b59e 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -235,8 +235,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
       <link linkend="sql-createsubscription-params-with-password-required"><literal>password_required</literal></link>,
       <link linkend="sql-createsubscription-params-with-run-as-owner"><literal>run_as_owner</literal></link>,
       <link linkend="sql-createsubscription-params-with-origin"><literal>origin</literal></link>,
-      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>, and
-      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>.
+      <link linkend="sql-createsubscription-params-with-failover"><literal>failover</literal></link>,
+      <link linkend="sql-createsubscription-params-with-two-phase"><literal>two_phase</literal></link>, and
+      <link linkend="sql-createsubscription-params-with-detect-conflict"><literal>detect_conflict</literal></link>.
       Only a superuser can set <literal>password_required = false</literal>.
      </para>
 
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 740b7d9421..067131337f 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -428,6 +428,98 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          </para>
         </listitem>
        </varlistentry>
+
+      <varlistentry id="sql-createsubscription-params-with-detect-conflict">
+        <term><literal>detect_conflict</literal> (<type>boolean</type>)</term>
+        <listitem>
+         <para>
+          Specifies whether the subscription is enabled for conflict detection.
+          The default is <literal>false</literal>.
+         </para>
+         <para>
+          When conflict detection is enabled, additional logging is triggered
+          in the following scenarios:
+          <variablelist>
+           <varlistentry>
+            <term><literal>insert_exists</literal></term>
+            <listitem>
+             <para>
+              Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to log the origin and commit
+              timestamp details of the conflicting key,
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              should be enabled. In this case, an error will be raised until the
+              conflict is resolved manually.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_differ</literal></term>
+            <listitem>
+             <para>
+              Updating a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled on the subscriber. Currenly, the update is always
+              applied regardless of the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_exists</literal></term>
+            <listitem>
+             <para>
+              The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint. Note that to log the origin and commit
+              timestamp details of the conflicting key,
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              should be enabled on the subscriber. In this case, an error will be
+              raised until the conflict is resolved manually. Note that when
+              updating a partitioned table, if the updated row value satisfies
+              another partition constraint resulting in the row being inserted
+              into a new partition, the <literal>insert_exists</literal>
+              conflict may arise if the new row violates a <literal>NOT DEFERRABLE</literal>
+              unique constraint.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>update_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be updated was not found. The update will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_differ</literal></term>
+            <listitem>
+             <para>
+              Deleting a row that was previously modified by another origin.
+              Note that this conflict can only be detected when
+              <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+              is enabled on the subscriber. Currenly, the delete is always
+              applied regardless of the origin of the local row.
+             </para>
+            </listitem>
+           </varlistentry>
+           <varlistentry>
+            <term><literal>delete_missing</literal></term>
+            <listitem>
+             <para>
+              The tuple to be deleted was not found. The delete will simply be
+              skipped in this scenario.
+             </para>
+            </listitem>
+           </varlistentry>
+          </variablelist>
+          Note that there are other conflict scenarios, such as exclusion
+          constraint violations. Currently, we do not provide additional
+          details for them in the log.
+         </para>
+        </listitem>
+       </varlistentry>
       </variablelist></para>
 
     </listitem>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index 9efc9159f2..5a423f4fb0 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -72,6 +72,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->passwordrequired = subform->subpasswordrequired;
 	sub->runasowner = subform->subrunasowner;
 	sub->failover = subform->subfailover;
+	sub->detectconflict = subform->subdetectconflict;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttrNotNull(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..d084bfc48a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1356,7 +1356,8 @@ REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
 			  subpasswordrequired, subrunasowner, subfailover,
-              subslotname, subsynccommit, subpublications, suborigin)
+			  subdetectconflict, subslotname, subsynccommit,
+			  subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index d124bfe55c..a949d246df 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -14,6 +14,7 @@
 
 #include "postgres.h"
 
+#include "access/commit_ts.h"
 #include "access/htup_details.h"
 #include "access/table.h"
 #include "access/twophase.h"
@@ -71,8 +72,9 @@
 #define SUBOPT_PASSWORD_REQUIRED	0x00000800
 #define SUBOPT_RUN_AS_OWNER			0x00001000
 #define SUBOPT_FAILOVER				0x00002000
-#define SUBOPT_LSN					0x00004000
-#define SUBOPT_ORIGIN				0x00008000
+#define SUBOPT_DETECT_CONFLICT		0x00004000
+#define SUBOPT_LSN					0x00008000
+#define SUBOPT_ORIGIN				0x00010000
 
 /* check if the 'val' has 'bits' set */
 #define IsSet(val, bits)  (((val) & (bits)) == (bits))
@@ -98,6 +100,7 @@ typedef struct SubOpts
 	bool		passwordrequired;
 	bool		runasowner;
 	bool		failover;
+	bool		detectconflict;
 	char	   *origin;
 	XLogRecPtr	lsn;
 } SubOpts;
@@ -112,6 +115,7 @@ static List *merge_publications(List *oldpublist, List *newpublist, bool addpub,
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
 static void CheckAlterSubOption(Subscription *sub, const char *option,
 								bool slot_needs_update, bool isTopLevel);
+static void check_conflict_detection(void);
 
 
 /*
@@ -162,6 +166,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 		opts->runasowner = false;
 	if (IsSet(supported_opts, SUBOPT_FAILOVER))
 		opts->failover = false;
+	if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT))
+		opts->detectconflict = false;
 	if (IsSet(supported_opts, SUBOPT_ORIGIN))
 		opts->origin = pstrdup(LOGICALREP_ORIGIN_ANY);
 
@@ -307,6 +313,15 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			opts->specified_opts |= SUBOPT_FAILOVER;
 			opts->failover = defGetBoolean(defel);
 		}
+		else if (IsSet(supported_opts, SUBOPT_DETECT_CONFLICT) &&
+				 strcmp(defel->defname, "detect_conflict") == 0)
+		{
+			if (IsSet(opts->specified_opts, SUBOPT_DETECT_CONFLICT))
+				errorConflictingDefElem(defel, pstate);
+
+			opts->specified_opts |= SUBOPT_DETECT_CONFLICT;
+			opts->detectconflict = defGetBoolean(defel);
+		}
 		else if (IsSet(supported_opts, SUBOPT_ORIGIN) &&
 				 strcmp(defel->defname, "origin") == 0)
 		{
@@ -594,7 +609,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					  SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
 					  SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT |
 					  SUBOPT_DISABLE_ON_ERR | SUBOPT_PASSWORD_REQUIRED |
-					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER | SUBOPT_ORIGIN);
+					  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
+					  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 	parse_subscription_options(pstate, stmt->options, supported_opts, &opts);
 
 	/*
@@ -639,6 +655,9 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 				 errmsg("password_required=false is superuser-only"),
 				 errhint("Subscriptions with the password_required option set to false may only be created or modified by the superuser.")));
 
+	if (opts.detectconflict)
+		check_conflict_detection();
+
 	/*
 	 * If built with appropriate switch, whine when regression-testing
 	 * conventions for subscription names are violated.
@@ -701,6 +720,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subpasswordrequired - 1] = BoolGetDatum(opts.passwordrequired);
 	values[Anum_pg_subscription_subrunasowner - 1] = BoolGetDatum(opts.runasowner);
 	values[Anum_pg_subscription_subfailover - 1] = BoolGetDatum(opts.failover);
+	values[Anum_pg_subscription_subdetectconflict - 1] =
+		BoolGetDatum(opts.detectconflict);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
@@ -1196,7 +1217,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 								  SUBOPT_DISABLE_ON_ERR |
 								  SUBOPT_PASSWORD_REQUIRED |
 								  SUBOPT_RUN_AS_OWNER | SUBOPT_FAILOVER |
-								  SUBOPT_ORIGIN);
+								  SUBOPT_DETECT_CONFLICT | SUBOPT_ORIGIN);
 
 				parse_subscription_options(pstate, stmt->options,
 										   supported_opts, &opts);
@@ -1356,6 +1377,16 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 					replaces[Anum_pg_subscription_subfailover - 1] = true;
 				}
 
+				if (IsSet(opts.specified_opts, SUBOPT_DETECT_CONFLICT))
+				{
+					values[Anum_pg_subscription_subdetectconflict - 1] =
+						BoolGetDatum(opts.detectconflict);
+					replaces[Anum_pg_subscription_subdetectconflict - 1] = true;
+
+					if (opts.detectconflict)
+						check_conflict_detection();
+				}
+
 				if (IsSet(opts.specified_opts, SUBOPT_ORIGIN))
 				{
 					values[Anum_pg_subscription_suborigin - 1] =
@@ -2536,3 +2567,18 @@ defGetStreamingMode(DefElem *def)
 					def->defname)));
 	return LOGICALREP_STREAM_OFF;	/* keep compiler quiet */
 }
+
+/*
+ * Report a warning about incomplete conflict detection if
+ * track_commit_timestamp is disabled.
+ */
+static void
+check_conflict_detection(void)
+{
+	if (!track_commit_timestamp)
+		ereport(WARNING,
+				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				errmsg("conflict detection could be incomplete due to disabled track_commit_timestamp"),
+				errdetail("Conflicts update_differ and delete_differ cannot be detected, "
+						  "and the origin and commit timestamp for the local row will not be logged."));
+}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b09d780fc5..7e9fab5b06 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2459,8 +2459,10 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, true);
-	InitConflictIndexes(relinfo);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
+
+	if (MySubscription->detectconflict)
+		InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2648,7 +2650,7 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, true);
+	ExecOpenIndices(relinfo, MySubscription->detectconflict);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
@@ -2668,9 +2670,11 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Report the conflict if the tuple was modified by a different origin.
+		 * Report the conflict if conflict detection is enabled and the tuple
+		 * was modified by a different origin.
 		 */
-		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2682,7 +2686,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
-		InitConflictIndexes(relinfo);
+		if (MySubscription->detectconflict)
+			InitConflictIndexes(relinfo);
 
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
@@ -2695,8 +2700,9 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_UPDATE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -2824,9 +2830,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Report the conflict if the tuple was modified by a different origin.
+		 * Report the conflict if conflict detection is enabled and the tuple
+		 * was modified by a different origin.
 		 */
-		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+		if (MySubscription->detectconflict &&
+			GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
 			ReportApplyConflict(LOG, CT_DELETE_DIFFER, localrel, InvalidOid,
 								localxmin, localorigin, localts, NULL);
@@ -2843,8 +2851,9 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
 		 */
-		ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
-							InvalidTransactionId, InvalidRepOriginId, 0, NULL);
+		if (MySubscription->detectconflict)
+			ReportApplyConflict(LOG, CT_DELETE_MISSING, localrel, InvalidOid,
+								InvalidTransactionId, InvalidRepOriginId, 0, NULL);
 	}
 
 	/* Cleanup. */
@@ -3027,18 +3036,21 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
 					 */
-					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
-										partrel, InvalidOid,
-										InvalidTransactionId,
-										InvalidRepOriginId, 0, NULL);
+					if (MySubscription->detectconflict)
+						ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+											partrel, InvalidOid,
+											InvalidTransactionId,
+											InvalidRepOriginId, 0, NULL);
 
 					return;
 				}
 
 				/*
-				 * Report the conflict if the tuple was modified by a different origin.
+				 * Report the conflict if conflict detection is enabled and the
+				 * tuple was modified by a different origin.
 				 */
-				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+				if (MySubscription->detectconflict &&
+					GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)
 					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrel,
 										InvalidOid, localxmin, localorigin,
@@ -3070,8 +3082,10 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
-					ExecOpenIndices(partrelinfo, true);
-					InitConflictIndexes(partrelinfo);
+					ExecOpenIndices(partrelinfo, MySubscription->detectconflict);
+
+					if (MySubscription->detectconflict)
+						InitConflictIndexes(partrelinfo);
 
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 79190470f7..84f374ea6a 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4800,6 +4800,7 @@ getSubscriptions(Archive *fout)
 	int			i_suboriginremotelsn;
 	int			i_subenabled;
 	int			i_subfailover;
+	int			i_subdetectconflict;
 	int			i,
 				ntups;
 
@@ -4872,11 +4873,17 @@ getSubscriptions(Archive *fout)
 
 	if (fout->remoteVersion >= 170000)
 		appendPQExpBufferStr(query,
-							 " s.subfailover\n");
+							 " s.subfailover,\n");
 	else
 		appendPQExpBuffer(query,
-						  " false AS subfailover\n");
+						  " false AS subfailover,\n");
 
+	if (fout->remoteVersion >= 170000)
+		appendPQExpBufferStr(query,
+							 " s.subdetectconflict\n");
+	else
+		appendPQExpBuffer(query,
+						  " false AS subdetectconflict\n");
 	appendPQExpBufferStr(query,
 						 "FROM pg_subscription s\n");
 
@@ -4915,6 +4922,7 @@ getSubscriptions(Archive *fout)
 	i_suboriginremotelsn = PQfnumber(res, "suboriginremotelsn");
 	i_subenabled = PQfnumber(res, "subenabled");
 	i_subfailover = PQfnumber(res, "subfailover");
+	i_subdetectconflict = PQfnumber(res, "subdetectconflict");
 
 	subinfo = pg_malloc(ntups * sizeof(SubscriptionInfo));
 
@@ -4961,6 +4969,8 @@ getSubscriptions(Archive *fout)
 			pg_strdup(PQgetvalue(res, i, i_subenabled));
 		subinfo[i].subfailover =
 			pg_strdup(PQgetvalue(res, i, i_subfailover));
+		subinfo[i].subdetectconflict =
+			pg_strdup(PQgetvalue(res, i, i_subdetectconflict));
 
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(subinfo[i].dobj), fout);
@@ -5201,6 +5211,9 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subfailover, "t") == 0)
 		appendPQExpBufferStr(query, ", failover = true");
 
+	if (strcmp(subinfo->subdetectconflict, "t") == 0)
+		appendPQExpBufferStr(query, ", detect_conflict = true");
+
 	if (strcmp(subinfo->subsynccommit, "off") != 0)
 		appendPQExpBuffer(query, ", synchronous_commit = %s", fmtId(subinfo->subsynccommit));
 
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 4b2e5870a9..bbd7cbeff6 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -671,6 +671,7 @@ typedef struct _SubscriptionInfo
 	char	   *suborigin;
 	char	   *suboriginremotelsn;
 	char	   *subfailover;
+	char	   *subdetectconflict;
 } SubscriptionInfo;
 
 /*
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 7c9a1f234c..fef1ad0d70 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -6539,7 +6539,7 @@ describeSubscriptions(const char *pattern, bool verbose)
 	printQueryOpt myopt = pset.popt;
 	static const bool translate_columns[] = {false, false, false, false,
 		false, false, false, false, false, false, false, false, false, false,
-	false};
+	false, false};
 
 	if (pset.sversion < 100000)
 	{
@@ -6607,6 +6607,10 @@ describeSubscriptions(const char *pattern, bool verbose)
 			appendPQExpBuffer(&buf,
 							  ", subfailover AS \"%s\"\n",
 							  gettext_noop("Failover"));
+		if (pset.sversion >= 170000)
+			appendPQExpBuffer(&buf,
+							  ", subdetectconflict AS \"%s\"\n",
+							  gettext_noop("Detect conflict"));
 
 		appendPQExpBuffer(&buf,
 						  ",  subsynccommit AS \"%s\"\n"
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 024469474d..1c416cf527 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1946,9 +1946,10 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("(", "PUBLICATION");
 	/* ALTER SUBSCRIPTION <name> SET ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SET", "("))
-		COMPLETE_WITH("binary", "disable_on_error", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+		COMPLETE_WITH("binary", "detect_conflict", "disable_on_error",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 	/* ALTER SUBSCRIPTION <name> SKIP ( */
 	else if (HeadMatches("ALTER", "SUBSCRIPTION", MatchAny) && TailMatches("SKIP", "("))
 		COMPLETE_WITH("lsn");
@@ -3357,9 +3358,10 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE SUBSCRIPTION <name> ...  WITH ( <opt>" */
 	else if (HeadMatches("CREATE", "SUBSCRIPTION") && TailMatches("WITH", "("))
 		COMPLETE_WITH("binary", "connect", "copy_data", "create_slot",
-					  "disable_on_error", "enabled", "failover", "origin",
-					  "password_required", "run_as_owner", "slot_name",
-					  "streaming", "synchronous_commit", "two_phase");
+					  "detect_conflict", "disable_on_error", "enabled",
+					  "failover", "origin", "password_required",
+					  "run_as_owner", "slot_name", "streaming",
+					  "synchronous_commit", "two_phase");
 
 /* CREATE TRIGGER --- is allowed inside CREATE SCHEMA, so use TailMatches */
 
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 0aa14ec4a2..17daf11dc7 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -98,6 +98,9 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
 
+	bool		subdetectconflict;	/* True if replication should perform
+									 * conflict detection */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -151,6 +154,7 @@ typedef struct Subscription
 								 * (i.e. the main slot and the table sync
 								 * slots) in the upstream database are enabled
 								 * to be synchronized to the standbys. */
+	bool		detectconflict; /* True if conflict detection is enabled */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 17d48b1685..118f207df5 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -116,18 +116,18 @@ CREATE SUBSCRIPTION regress_testsub4 CONNECTION 'dbname=regress_doesnotexist' PU
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | none   | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
 \dRs+ regress_testsub4
-                                                                                                                 List of subscriptions
-       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
-------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                          List of subscriptions
+       Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub4 | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub3;
@@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
 ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | f                 | t             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
@@ -176,10 +176,10 @@ ERROR:  unrecognized subscription parameter: "create_slot"
 -- ok
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/12345');
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/12345
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/12345
 (1 row)
 
 -- ok - with lsn = NONE
@@ -188,10 +188,10 @@ ALTER SUBSCRIPTION regress_testsub SKIP (lsn = NONE);
 ALTER SUBSCRIPTION regress_testsub SKIP (lsn = '0/0');
 ERROR:  invalid WAL location (LSN): 0/0
 \dRs+
-                                                                                                                     List of subscriptions
-      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                              List of subscriptions
+      Name       |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 BEGIN;
@@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
 ERROR:  invalid value for parameter "synchronous_commit": "foobar"
 HINT:  Available values: local, remote_write, remote_apply, on, off.
 \dRs+
-                                                                                                                       List of subscriptions
-        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |           Conninfo           | Skip LSN 
----------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+------------------------------+----------
- regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | local              | dbname=regress_doesnotexist2 | 0/0
+                                                                                                                                List of subscriptions
+        Name         |           Owner           | Enabled |     Publication     | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |           Conninfo           | Skip LSN 
+---------------------+---------------------------+---------+---------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+------------------------------+----------
+ regress_testsub_foo | regress_subscription_user | f       | {testpub2,testpub3} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | local              | dbname=regress_doesnotexist2 | 0/0
 (1 row)
 
 -- rename back to keep the rest simple
@@ -255,19 +255,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | t      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (binary = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -279,27 +279,27 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | parallel  | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication already exists
@@ -314,10 +314,10 @@ ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refr
 ALTER SUBSCRIPTION regress_testsub ADD PUBLICATION testpub1, testpub2 WITH (refresh = false);
 ERROR:  publication "testpub1" is already in subscription "regress_testsub"
 \dRs+
-                                                                                                                        List of subscriptions
-      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                                 List of subscriptions
+      Name       |           Owner           | Enabled |         Publication         | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-----------------------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub,testpub1,testpub2} | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- fail - publication used more than once
@@ -332,10 +332,10 @@ ERROR:  publication "testpub3" is not in subscription "regress_testsub"
 -- ok - delete publications
 ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
@@ -371,19 +371,19 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 -- we can alter streaming when two_phase enabled
 ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -393,10 +393,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | on        | p                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
@@ -409,18 +409,54 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 WARNING:  subscription was created, but is not connected
 HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 \dRs+
-                                                                                                                List of subscriptions
-      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit |          Conninfo           | Skip LSN 
------------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+--------------------+-----------------------------+----------
- regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | off                | dbname=regress_doesnotexist | 0/0
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | t                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+ERROR:  detect_conflict requires a Boolean value
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | f               | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+WARNING:  conflict detection could be incomplete due to disabled track_commit_timestamp
+DETAIL:  Conflicts update_differ and delete_differ cannot be detected, and the origin and commit timestamp for the local row will not be logged.
+\dRs+
+                                                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Detect conflict | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+-------------------+---------------+----------+-----------------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | off       | d                | f                | any    | t                 | f             | f        | t               | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 007c9e7037..b3f2ab1684 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -287,6 +287,25 @@ ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 DROP SUBSCRIPTION regress_testsub;
 
+-- fail - detect_conflict must be boolean
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = foo);
+
+-- now it works, but will report a warning due to disabled track_commit_timestamp
+CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = false);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (detect_conflict = true);
+
+\dRs+
+
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
+DROP SUBSCRIPTION regress_testsub;
+
 -- let's do some tests with pg_create_subscription rather than superuser
 SET SESSION AUTHORIZATION regress_subscription_user3;
 
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 79cbed2e5b..78c0307165 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,6 +331,13 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET (detect_conflict = true)"
+);
+
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
 
 # Note that the current location of the log file is not grabbed immediately
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 896985d85b..a3effed937 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,6 +343,13 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = true)"
+);
+
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -377,6 +384,10 @@ ok( $logfile =~
 	  qr/conflict delete_missing detected on relation "public.tab1_def".*\n.*DETAIL:.* Did not find the row to be deleted./,
 	'delete target row is missing in tab1_def');
 
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub1 SET (detect_conflict = false)"
+);
+
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -762,6 +773,13 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
+# To check that subscriber handles cases where update/delete target tuple
+# is missing, detect_conflict is temporarily enabled to log conflicts
+# related to missing tuples.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = true)"
+);
+
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -800,6 +818,11 @@ ok( $logfile =~
 	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
 	'updating a tuple that was modified by a different origin');
 
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub_viaroot SET (detect_conflict = false)"
+);
+
 $node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_subscriber1->restart;
 
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index ac7c8bbe7c..b71d0c3400 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -111,7 +111,7 @@ my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub FOR TABLE tbl");
 $node_subscriber->safe_psql('postgres',
-	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on)"
+	"CREATE SUBSCRIPTION sub CONNECTION '$publisher_connstr' PUBLICATION pub WITH (disable_on_error = true, streaming = on, two_phase = on, detect_conflict = on)"
 );
 
 # Initial synchronization failure causes the subscription to be disabled.
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 5a22413464..6bc4474d15 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -149,7 +149,9 @@ is($result, qq(),
 # delete a row that was previously modified by a different source.
 ###############################################################################
 
-$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = true);
+	 DELETE FROM tab;");
 
 $node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
 
@@ -183,6 +185,9 @@ $node_B->wait_for_log(
 );
 
 # The remaining tests no longer test conflict detection.
+$node_B->safe_psql('postgres',
+	"ALTER SUBSCRIPTION $subname_BC SET (detect_conflict = false);");
+
 $node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
 $node_B->restart;
 
-- 
2.30.0.windows.2

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 57216d6c52..cd92f6a7d5 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1595,8 +1595,8 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
        unique constraint. Note that to log the origin and commit
        timestamp details of the conflicting key,
        <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
-       should be enabled. In this case, an error will be raised until the
-       conflict is resolved manually.
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
       </para>
      </listitem>
     </varlistentry>
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index 09b51706db..b8a6de5eca 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -549,8 +549,9 @@ CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
 			TransactionId xmin;
 
 			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
-			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc, uniqueidx,
-								xmin, origin, committs, conflictslot);
+			ReportApplyConflict(ERROR, type, resultRelInfo->ri_RelationDesc,
+								uniqueidx, xmin, origin, committs,
+								conflictslot);
 		}
 	}
 }
@@ -623,8 +624,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		 *
 		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
 		 * in heap and index in case of conflicts. But as conflicts shouldn't
-		 * be a frequent thing so we preferred to save the performance overhead
-		 * of extra scan before each insertion.
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
 		 */
 		if (conflict)
 			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index c69194244c..27e7cb1950 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -20,7 +20,7 @@
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 
-const char *const ConflictTypeNames[] = {
+static const char *const ConflictTypeNames[] = {
 	[CT_INSERT_EXISTS] = "insert_exists",
 	[CT_UPDATE_DIFFER] = "update_differ",
 	[CT_UPDATE_EXISTS] = "update_exists",
@@ -211,9 +211,15 @@ errdetail_apply_conflict(ConflictType type, Oid conflictidx,
 			}
 		case CT_DELETE_MISSING:
 			return errdetail("Did not find the row to be deleted.");
-	}
 
-	return 0;					/* silence compiler warning */
+		/*
+		 * XXX should we add a default behavior instead of just returning zero?
+		 * This style can detect mistakes of coding.
+		 */
+		default:
+			elog(ERROR, "unexpected conflict type: %d", (int) type);
+			return 0;		/* silence compiler warning */
+	}
 }
 
 /*
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index b09d780fc5..105af9775c 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2668,7 +2668,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Report the conflict if the tuple was modified by a different origin.
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
 		 */
 		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
@@ -2824,7 +2825,8 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		TimestampTz localts;
 
 		/*
-		 * Report the conflict if the tuple was modified by a different origin.
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
 		 */
 		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
 			localorigin != replorigin_session_origin)
@@ -3036,7 +3038,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				}
 
 				/*
-				 * Report the conflict if the tuple was modified by a different origin.
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
 				 */
 				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
 					localorigin != replorigin_session_origin)
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index e9ba6818fc..1d466c3cad 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -45,12 +45,16 @@ typedef enum
 	 */
 } ConflictType;
 
-extern bool GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
-									RepOriginId *localorigin, TimestampTz *localts);
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
 extern void ReportApplyConflict(int elevel, ConflictType type,
 								Relation localrel, Oid conflictidx,
-								TransactionId localxmin, RepOriginId localorigin,
-								TimestampTz localts, TupleTableSlot *conflictslot);
+								TransactionId localxmin,
+								RepOriginId localorigin,
+								TimestampTz localts,
+								TupleTableSlot *conflictslot);
 extern void InitConflictIndexes(ResultRelInfo *relInfo);
 
 #endif
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 896985d85b..e26f26acc5 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -786,10 +786,12 @@ ok( $logfile =~
 
 # Enable the track_commit_timestamp to detect the conflict when attempting
 # to update a row that was previously modified by a different origin.
-$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
 $node_subscriber1->restart;
 
-$node_subscriber1->safe_psql('postgres', "INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
 
@@ -800,7 +802,9 @@ ok( $logfile =~
 	  qr/conflict update_differ detected on relation "public.tab2_1".*\n.*DETAIL:.* Updating a row that was modified locally in transaction [0-9]+ at .*/,
 	'updating a tuple that was modified by a different origin');
 
-$node_subscriber1->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+# The remaining tests no longer test conflict detection.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = off');
 $node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the

From 17c0c5030e43b8338375c69f0c8f48edb883beaf Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v12] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 235 +++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 475 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 120 ++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  60 +++
 src/test/subscription/out                   |  29 ++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++
 src/tools/pgindent/typedefs.list            |   1 +
 19 files changed, 1055 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h
 create mode 100644 src/test/subscription/out

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..5e5dd4adaf 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict insert_exists detected on relation "public.test"
+DETAIL:  Key (c)=(1) already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..21a945923a 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint and logical replication
+ * tuple missing conflict error messages so only key columns of the index are
+ * checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..2758daa4e1 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,88 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, resultRelInfo, uniqueidx,
+								xmin, origin, committs, NULL, conflictslot,
+								slot, estate);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +585,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +603,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +678,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +696,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..65504483fb
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,475 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "catalog/index.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static char *build_tuple_value_desc(Relation localrel, TupleTableSlot *slot);
+static char *build_tuple_value_details(ResultRelInfo *relinfo,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   EState *estate);
+static char *build_index_value_desc(Relation localrel, Oid indexoid,
+									TupleTableSlot *slot,
+									EState *estate);
+static int	errdetail_apply_conflict(ConflictType type, ResultRelInfo *relinfo,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 EState *estate);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ *
+ * The 'indexoid' represents the OID of the replica identity index or the OID
+ * of the unique index that triggered the constraint violation error. The
+ * caller should ensure that the index with the OID 'indexoid' is locked.
+ *
+ * 'searchslot' should contain the tuple used to search for the local tuple to
+ * be updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localorigin' provide
+ * the transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * Refer to errdetail_apply_conflict for the content that will be included in
+ * the DETAIL line.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, ResultRelInfo *relinfo,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts,
+					TupleTableSlot *searchslot, TupleTableSlot *localslot,
+					TupleTableSlot *remoteslot,
+					EState *estate)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(type, relinfo, indexoid, localxmin,
+									 localorigin, localts, searchslot,
+									 localslot, remoteslot, estate));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises two parts:
+ * 1. Explanation of the conflict type, including the tuple value used to
+ *    search the existing local tuple provided for update or deletion, or the
+ *    tuple value causing the unique constraint violation.
+ * 2. Display of the complete existing local tuple and the remote new tuple, if
+ *    any. The remote old tuple is excluded as its information is covered in
+ *    the search tuple mentioned in part 1.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, ResultRelInfo *relinfo,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts,
+						 TupleTableSlot *searchslot, TupleTableSlot *localslot,
+						 TupleTableSlot *remoteslot, EState *estate)
+{
+	StringInfoData err_detail;
+	Relation	localrel = relinfo->ri_RelationDesc;
+	char	   *val_desc;
+	char	   *origin_name;
+	TupleTableSlot *slot = searchslot ? searchslot : localslot;
+
+	initStringInfo(&err_detail);
+
+	/*
+	 * If a valid index OID is provided, build the index value string.
+	 * Otherwise, construct the full tuple value for REPLICA IDENTITY FULL
+	 * cases. If the returned string is NULL, it indicates that the current
+	 * user lacks permissions to view all the columns involved.
+	 */
+	if (OidIsValid(indexoid))
+		val_desc = build_index_value_desc(localrel, indexoid, slot, estate);
+	else
+		val_desc = build_tuple_value_desc(localrel, slot);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			/*
+			 * User don't need SELECT permissions to apply an INSERT
+			 * operation, so 'val_desc' could be NULL in cases where
+			 * permission is lacking.
+			 */
+			if (val_desc && localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key %s already exists in unique index \"%s\", which was modified locally in transaction %u at %s."),
+									 val_desc, get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key %s already exists in unique index \"%s\", which was modified by origin \"%s\" in transaction %u at %s."),
+									 val_desc, get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin which modified the row has been dropped. This
+				 * situation may occur if the origin was created by a
+				 * different apply worker, but its associated subscription and
+				 * origin were dropped after updating the row, or if the
+				 * origin was manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key %s already exists in unique index \"%s\", which was modified by a non-existent origin in transaction %u at %s."),
+									 val_desc, get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else if (val_desc && !localts)
+				appendStringInfo(&err_detail, _("Key %s already exists in unique index \"%s\", which was modified in transaction %u."),
+								 val_desc, get_rel_name(indexoid), localxmin);
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\"."),
+								 get_rel_name(indexoid));
+			break;
+
+		case CT_UPDATE_DIFFER:
+
+			/*
+			 * Although users must have table-level SELECT permissions to
+			 * perform an UPDATE or DELETE operation, these privileges could
+			 * be revoked just before conflict reporting. Therefore, we cannot
+			 * assume we can get the valid val_desc.
+			 */
+			if (val_desc)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Updating the row containing %s that was modified locally in transaction %u at %s."),
+									 val_desc, localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Updating the row containing %s that was modified by a different origin \"%s\" in transaction %u at %s."),
+									 val_desc, origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					appendStringInfo(&err_detail, _("Updating the row containing %s that was modified by a non-existent origin in transaction %u at %s."),
+									 val_desc, localxmin, timestamptz_to_str(localts));
+			}
+			else
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			break;
+
+		case CT_UPDATE_MISSING:
+
+			/*
+			 * See the comments in the update_differ case to understand why
+			 * 'val_desc' could be NULL.
+			 */
+			if (val_desc)
+				appendStringInfo(&err_detail, _("Did not find the row containing %s to be updated."),
+								 val_desc);
+			else
+				appendStringInfo(&err_detail, _("Did not find the row to be updated."));
+
+			break;
+
+		case CT_DELETE_DIFFER:
+
+			/*
+			 * See the comments in the update_differ case to understand why
+			 * 'val_desc' could be NULL.
+			 */
+			if (val_desc)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Deleting the row containing %s that was modified by locally in transaction %u at %s."),
+									 val_desc, localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Deleting the row containing %s that was modified by a different origin \"%s\" in transaction %u at %s."),
+									 val_desc, origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					appendStringInfo(&err_detail, _("Deleting the row containing %s that was modified by a non-existent origin in transaction %u at %s."),
+									 val_desc, localxmin, timestamptz_to_str(localts));
+			}
+			else
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Deleting the row that was modified by locally in transaction %u at %s."),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+									 origin_name, localxmin, timestamptz_to_str(localts));
+
+				/* The origin which modified the row has been dropped */
+				else
+					appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			break;
+
+		case CT_DELETE_MISSING:
+
+			/*
+			 * See the comments in the update_differ case to understand why
+			 * 'val_desc' could be NULL.
+			 */
+			if (val_desc)
+				appendStringInfo(&err_detail, _("Did not find the row containing %s to be deleted."),
+								 val_desc);
+			else
+				appendStringInfo(&err_detail, _("Did not find the row to be deleted."));
+
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(relinfo, localslot, remoteslot,
+										 estate);
+
+	/*
+	 * Next, append the existing local tuple and remote tuple values after the
+	 * message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * A wrapper function of ExecBuildSlotValueDescription.
+ */
+static char *
+build_tuple_value_desc(Relation localrel, TupleTableSlot *slot)
+{
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	char	   *tuple_value;
+
+	tuple_value = ExecBuildSlotValueDescription(relid, slot, tupdesc,
+												NULL, 64);
+
+	return tuple_value;
+}
+
+/*
+ * Helper function to build the additional details after the main DETAIL line
+ * that describes the values of the existing local tuple and the remote tuple.
+ */
+static char *
+build_tuple_value_details(ResultRelInfo *relinfo,
+						  TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						  EState *estate)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	char	   *local_tuple_value = NULL;
+	char	   *remote_tuple_value = NULL;
+	StringInfoData tuple_value;
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies the new tuple, hence we pass NULL
+		 * for the existing local tuple.
+		 */
+		local_tuple_value = ExecBuildSlotValueDescription(relid, localslot,
+														  tupdesc, NULL, 64);
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		remote_tuple_value = ExecBuildSlotValueDescription(relid, remoteslot,
+														   tupdesc,
+														   modifiedCols, 64);
+	}
+
+	initStringInfo(&tuple_value);
+
+	if (local_tuple_value && !remote_tuple_value)
+		appendStringInfo(&tuple_value, _("Existing local tuple %s."),
+						 local_tuple_value);
+	else if (local_tuple_value && remote_tuple_value)
+		appendStringInfo(&tuple_value, _("Existing local tuple %s; remote tuple %s."),
+						 local_tuple_value, remote_tuple_value);
+	else if (!local_tuple_value && remote_tuple_value)
+		appendStringInfo(&tuple_value, _("Remote tuple %s."),
+						 remote_tuple_value);
+	else
+		return NULL;
+
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'indexoid' is locked.
+ */
+static char *
+build_index_value_desc(Relation localrel, Oid indexoid, TupleTableSlot *slot,
+					   EState *estate)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6dc54c7283..e70624d1b4 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,13 +2648,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2661,6 +2662,29 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, relinfo,
+								GetRelationIdentityOrPK(localrel),
+								localxmin, localorigin, localts, remoteslot,
+								localslot, newslot, estate);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2692,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2675,16 +2701,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, relinfo,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0,
+							remoteslot, NULL, newslot, estate);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2836,21 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, relinfo,
+								GetRelationIdentityOrPK(localrel), localxmin,
+								localorigin, localts, remoteslot, localslot,
+								NULL, estate);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2862,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, relinfo,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0,
+							remoteslot, NULL, NULL, estate);
 	}
 
 	/* Cleanup. */
@@ -2992,6 +3034,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3000,19 +3045,46 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										partrelinfo,
+										GetRelationIdentityOrPK(partrel),
+										InvalidTransactionId,
+										InvalidRepOriginId, 0,
+										remoteslot_part, NULL, newslot,
+										estate);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, partrelinfo,
+										GetRelationIdentityOrPK(partrel),
+										localxmin, localorigin, localts,
+										remoteslot_part, localslot, newslot,
+										estate);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3023,7 +3095,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3040,6 +3111,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3087,6 +3161,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..ca4a3fddba
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,60 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve rules
+	 * that are more complex than simple equality checks. These conflicts are
+	 * left for future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type,
+								ResultRelInfo *relinfo, Oid indexoid,
+								TransactionId localxmin,
+								RepOriginId localorigin,
+								TimestampTz localts,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								EState *estate);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/out b/src/test/subscription/out
new file mode 100644
index 0000000000..2b68e9264a
--- /dev/null
+++ b/src/test/subscription/out
@@ -0,0 +1,29 @@
+make -C ../../../src/backend generated-headers
+make[1]: Entering directory '/home/houzj/postgresql/src/backend'
+make -C ../include/catalog generated-headers
+make[2]: Entering directory '/home/houzj/postgresql/src/include/catalog'
+make[2]: Nothing to be done for 'generated-headers'.
+make[2]: Leaving directory '/home/houzj/postgresql/src/include/catalog'
+make -C nodes generated-header-symlinks
+make[2]: Entering directory '/home/houzj/postgresql/src/backend/nodes'
+make[2]: Nothing to be done for 'generated-header-symlinks'.
+make[2]: Leaving directory '/home/houzj/postgresql/src/backend/nodes'
+make -C utils generated-header-symlinks
+make[2]: Entering directory '/home/houzj/postgresql/src/backend/utils'
+make -C adt jsonpath_gram.h
+make[3]: Entering directory '/home/houzj/postgresql/src/backend/utils/adt'
+make[3]: 'jsonpath_gram.h' is up to date.
+make[3]: Leaving directory '/home/houzj/postgresql/src/backend/utils/adt'
+make[2]: Leaving directory '/home/houzj/postgresql/src/backend/utils'
+make[1]: Leaving directory '/home/houzj/postgresql/src/backend'
+rm -rf '/home/houzj/postgresql'/tmp_install
+/usr/bin/mkdir -p '/home/houzj/postgresql'/tmp_install/log
+make -C '../../..' DESTDIR='/home/houzj/postgresql'/tmp_install install >'/home/houzj/postgresql'/tmp_install/log/install.log 2>&1
+make -j1  checkprep >>'/home/houzj/postgresql'/tmp_install/log/install.log 2>&1
+PATH="/home/houzj/postgresql/tmp_install/home/houzj/pgsql/bin:/home/houzj/postgresql/src/test/subscription:$PATH" LD_LIBRARY_PATH="/home/houzj/postgresql/tmp_install/home/houzj/pgsql/lib" INITDB_TEMPLATE='/home/houzj/postgresql'/tmp_install/initdb-template  initdb --auth trust --no-sync --no-instructions --lc-messages=C --no-clean '/home/houzj/postgresql'/tmp_install/initdb-template >>'/home/houzj/postgresql'/tmp_install/log/initdb-template.log 2>&1
+echo "# +++ tap check in src/test/subscription +++" && rm -rf '/home/houzj/postgresql/src/test/subscription'/tmp_check && /usr/bin/mkdir -p '/home/houzj/postgresql/src/test/subscription'/tmp_check && cd . && TESTLOGDIR='/home/houzj/postgresql/src/test/subscription/tmp_check/log' TESTDATADIR='/home/houzj/postgresql/src/test/subscription/tmp_check' PATH="/home/houzj/postgresql/tmp_install/home/houzj/pgsql/bin:/home/houzj/postgresql/src/test/subscription:$PATH" LD_LIBRARY_PATH="/home/houzj/postgresql/tmp_install/home/houzj/pgsql/lib" INITDB_TEMPLATE='/home/houzj/postgresql'/tmp_install/initdb-template  PGPORT='65432' top_builddir='/home/houzj/postgresql/src/test/subscription/../../..' PG_REGRESS='/home/houzj/postgresql/src/test/subscription/../../../src/test/regress/pg_regress' /usr/bin/prove -I ../../../src/test/perl/ -I .  t/013_partition.pl
+# +++ tap check in src/test/subscription +++
+t/013_partition.pl .. ok
+All tests successful.
+Files=1, Tests=73,  4 wallclock secs ( 0.02 usr  0.00 sys +  0.59 cusr  0.21 csys =  0.82 CPU)
+Result: PASS
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..88083ef084 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(1\) to be updated.*\n.*Remote tuple \(1, quux\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Did not find the row containing \(25\) to be updated.*\n.*Remote tuple \(26\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(2\) to be deleted.*/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..1362f2bdc8 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(4\) to be updated.*\n.*Remote tuple \(null, 4, quux\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(1\) to be deleted.*/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(4\) to be deleted.*/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(10\) to be deleted.*/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(5\) to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\)./,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row containing \(a\)=\(1\) to be deleted.*/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row containing \(a\)=\(3\) that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..1b6f3822c3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key \(i\)=\(\d+\) already exists in unique index "tbl_pkey", which was modified by .*origin.* transaction \d+ at .*\n.*Existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..4438e1ecbf 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row containing \(a\)=\(32\) that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row containing \(a\)=\(33\) that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 547d14b3e7..6d424c8918 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From 63d70937ef695fbcfdc57765a7c63066da1f4bf2 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v13] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 235 ++++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 445 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 118 +++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  58 +++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 +++
 src/tools/pgindent/typedefs.list            |   1 +
 18 files changed, 992 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..3c279a1083 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict detected on relation "public.test: conflict=insert_exists"
+DETAIL:  Key already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Key (c)=(1); existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..21a945923a 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint and logical replication
+ * tuple missing conflict error messages so only key columns of the index are
+ * checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..c8d821ca47 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,88 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(ERROR, type, estate, resultRelInfo,
+								NULL, conflictslot, slot, uniqueidx, xmin,
+								origin, committs);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +585,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +603,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +678,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +696,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..8f7e5bfdd4
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,445 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "catalog/index.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static int	errdetail_apply_conflict(ConflictType type, EState *estate,
+									 ResultRelInfo *relinfo,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts);
+static char *build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+									   TupleTableSlot *searchslot,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   Oid indexoid);
+static char *build_index_value_desc(EState *estate, Relation localrel,
+									TupleTableSlot *slot, Oid indexoid);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * Report a conflict when applying remote changes.
+ *
+ * 'searchslot' should contain the tuple used to search for the local tuple to
+ * be updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
+ * transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * The 'indexoid' represents the OID of the replica identity index or the OID
+ * of the unique index that triggered the constraint violation error. Note that
+ * while other indexes may also be used (see
+ * IsIndexUsableForReplicaIdentityFull for details) to find the tuple when
+ * applying update or delete, such an index scan may not result in a unique
+ * tuple and we still compare the complete tuple in such cases, thus such index
+ * OIDs should not be passed here.
+ *
+ * The caller should ensure that the index with the OID 'indexoid' is locked.
+ *
+ * Refer to errdetail_apply_conflict for the content that will be included in
+ * the DETAIL line.
+ */
+void
+ReportApplyConflict(int elevel, ConflictType type, EState *estate,
+					ResultRelInfo *relinfo, TupleTableSlot *searchslot,
+					TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(type, estate, relinfo, searchslot,
+									 localslot, remoteslot, indexoid,
+									 localxmin, localorigin, localts));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises two parts:
+ * 1. Explanation of the conflict type, including the origin and commit
+ *    timestamp of the existing local tuple.
+ * 2. Display of conflicting key, existing local tuple, remote new tuple and
+ *    replica identity columns, if any. The remote old tuple is excluded as its
+ *    information is covered in the replica identity columns.
+ */
+static int
+errdetail_apply_conflict(ConflictType type, EState *estate,
+						 ResultRelInfo *relinfo, TupleTableSlot *searchslot,
+						 TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts)
+{
+	StringInfoData err_detail;
+	char	   *val_desc;
+	char	   *origin_name;
+
+	initStringInfo(&err_detail);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			if (localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified locally in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by origin \"%s\" in transaction %u at %s."),
+									 get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin which modified the row has been dropped. This
+				 * situation may occur if the origin was created by a
+				 * different apply worker, but its associated subscription and
+				 * origin were dropped after updating the row, or if the
+				 * origin was manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified in transaction %u."),
+								 get_rel_name(indexoid), localxmin);
+
+			break;
+
+		case CT_UPDATE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin which modified the row has been dropped */
+			else
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_UPDATE_MISSING:
+			appendStringInfo(&err_detail, _("Did not find the row to be updated."));
+			break;
+
+		case CT_DELETE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Deleting the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin which modified the row has been dropped */
+			else
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_DELETE_MISSING:
+			appendStringInfo(&err_detail, _("Did not find the row to be deleted."));
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(estate, relinfo, searchslot,
+										 localslot, remoteslot, indexoid);
+
+	/*
+	 * Next, append the key values, existing local tuple, remote tuple and
+	 * replica identity columns after the message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * Helper function to build the additional details after the main DETAIL line
+ * that describes the values of the conflicting key, existing local tuple,
+ * remote tuple and replica identity columns.
+ *
+ * If the return value is NULL, it indicates that the current user lacks
+ * permissions to view all the columns involved.
+ */
+static char *
+build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+						  TupleTableSlot *searchslot,
+						  TupleTableSlot *localslot,
+						  TupleTableSlot *remoteslot,
+						  Oid indexoid)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	StringInfoData tuple_value;
+	char	   *desc = NULL;
+
+	Assert(searchslot || localslot || remoteslot);
+
+	initStringInfo(&tuple_value);
+
+	/*
+	 * If 'searchslot' is NULL and 'indexoid' is valid, it indicates that we
+	 * are reporting the unique constraint violation conflict, in which case
+	 * the conflicting key values will be reported.
+	 */
+	if (OidIsValid(indexoid) && !searchslot)
+	{
+		Assert(localslot);
+
+		desc = build_index_value_desc(estate, localrel, localslot, indexoid);
+
+		if (desc)
+			appendStringInfo(&tuple_value, _("Key %s"), desc);
+	}
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies to the new tuple, hence we pass
+		 * NULL for the existing local tuple.
+		 */
+		desc = ExecBuildSlotValueDescription(relid, localslot, tupdesc,
+											 NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("existing local tuple %s"),
+								 desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Existing local tuple %s"),
+								 desc);
+			}
+		}
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		desc = ExecBuildSlotValueDescription(relid, remoteslot, tupdesc,
+											 modifiedCols, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("remote tuple %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Remote tuple %s"), desc);
+			}
+		}
+	}
+
+	if (searchslot)
+	{
+		/*
+		 * If a valid index OID is provided, build the replica identity key
+		 * value string. Otherwise, construct the full tuple value for REPLICA
+		 * IDENTITY FULL cases.
+		 */
+		if (OidIsValid(indexoid))
+			desc = build_index_value_desc(estate, localrel, searchslot, indexoid);
+		else
+			desc = ExecBuildSlotValueDescription(relid, searchslot, tupdesc, NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("replica identity %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Replica identity %s"), desc);
+			}
+		}
+	}
+
+	if (tuple_value.len == 0)
+		return NULL;
+
+	appendStringInfoChar(&tuple_value, '.');
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'indexoid' is locked.
+ */
+static char *
+build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
+					   Oid indexoid)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6dc54c7283..23e837cfb1 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,13 +2648,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2661,6 +2662,29 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(LOG, CT_UPDATE_DIFFER, estate, relinfo,
+								remoteslot, localslot, newslot,
+								GetRelationIdentityOrPK(localrel),
+								localxmin, localorigin, localts);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2692,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2675,16 +2701,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_UPDATE_MISSING, estate, relinfo,
+							remoteslot, NULL, newslot,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2836,21 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(LOG, CT_DELETE_DIFFER, estate, relinfo,
+								remoteslot, localslot, NULL,
+								GetRelationIdentityOrPK(localrel), localxmin,
+								localorigin, localts);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2862,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(LOG, CT_DELETE_MISSING, estate, relinfo,
+							remoteslot, NULL, NULL,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2992,6 +3034,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3000,19 +3045,44 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(LOG, CT_UPDATE_MISSING,
+										estate, partrelinfo,
+										remoteslot_part, NULL, newslot,
+										GetRelationIdentityOrPK(partrel),
+										InvalidTransactionId,
+										InvalidRepOriginId, 0);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(LOG, CT_UPDATE_DIFFER, estate, partrelinfo,
+										remoteslot_part, localslot, newslot,
+										GetRelationIdentityOrPK(partrel),
+										localxmin, localorigin, localts);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3023,7 +3093,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3040,6 +3109,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3087,6 +3159,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..24fc8c8e64
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve rules
+	 * that are more complex than simple equality checks. These conflicts are
+	 * left for future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(int elevel, ConflictType type, EState *estate,
+								ResultRelInfo *relinfo,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								Oid indexoid, TransactionId localxmin,
+								RepOriginId localorigin, TimestampTz localts);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..e1759c4b2c 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Did not find the row to be updated.*\n.*Remote tuple \(1, quux\); replica identity \(a\)=\(1\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Did not find the row to be updated.*\n.*Remote tuple \(26\); replica identity \(25\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row to be deleted.*\n.*Replica identity \(a\)=\(2\)/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..21825d4792 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Did not find the row to be updated.*\n.*Remote tuple \(null, 4, quux\); replica identity \(a\)=\(4\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row to be deleted.*\n.*Replica identity \(a\)=\(4\)/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row to be deleted.*\n.*Replica identity \(a\)=\(10\)/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Did not find the row to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\); replica identity \(a\)=\(5\)/,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Did not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\); replica identity \(a\)=\(3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..2f099a74f3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key already exists in unique index "tbl_pkey", modified by .*origin.* transaction \d+ at .*\n.*Key \(i\)=\(\d+\); existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..01536a13e7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\); replica identity \(a\)=\(32\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\); replica identity \(a\)=\(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 547d14b3e7..6d424c8918 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 8f7e5bfdd4..4995651644 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -79,10 +79,11 @@ GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
 }
 
 /*
- * Report a conflict when applying remote changes.
+ * This function is used to report a conflict while applying replication
+ * changes.
  *
- * 'searchslot' should contain the tuple used to search for the local tuple to
- * be updated or deleted.
+ * 'searchslot' should contain the tuple used to search the local tuple to be
+ * updated or deleted.
  *
  * 'localslot' should contain the existing local tuple, if any, that conflicts
  * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
@@ -91,17 +92,17 @@ GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
  * 'remoteslot' should contain the remote new tuple, if any.
  *
  * The 'indexoid' represents the OID of the replica identity index or the OID
- * of the unique index that triggered the constraint violation error. Note that
- * while other indexes may also be used (see
+ * of the unique index that triggered the constraint violation error. We use
+ * this to report the key values for conflicting tuple.
+ *
+ * Note that while other indexes may also be used (see
  * IsIndexUsableForReplicaIdentityFull for details) to find the tuple when
  * applying update or delete, such an index scan may not result in a unique
  * tuple and we still compare the complete tuple in such cases, thus such index
  * OIDs should not be passed here.
  *
- * The caller should ensure that the index with the OID 'indexoid' is locked.
- *
- * Refer to errdetail_apply_conflict for the content that will be included in
- * the DETAIL line.
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can display the conflicting key value.
  */
 void
 ReportApplyConflict(int elevel, ConflictType type, EState *estate,
@@ -157,10 +158,10 @@ InitConflictIndexes(ResultRelInfo *relInfo)
 /*
  * Add an errdetail() line showing conflict detail.
  *
- * The DETAIL line comprises two parts:
+ * The DETAIL line comprises of two parts:
  * 1. Explanation of the conflict type, including the origin and commit
  *    timestamp of the existing local tuple.
- * 2. Display of conflicting key, existing local tuple, remote new tuple and
+ * 2. Display of conflicting key, existing local tuple, remote new tuple, and
  *    replica identity columns, if any. The remote old tuple is excluded as its
  *    information is covered in the replica identity columns.
  */
@@ -196,11 +197,11 @@ errdetail_apply_conflict(ConflictType type, EState *estate,
 									 localxmin, timestamptz_to_str(localts));
 
 				/*
-				 * The origin which modified the row has been dropped. This
-				 * situation may occur if the origin was created by a
-				 * different apply worker, but its associated subscription and
-				 * origin were dropped after updating the row, or if the
-				 * origin was manually dropped by the user.
+				 * The origin that modified this row has been removed. This
+				 * can happen if the origin was created by a different apply
+				 * worker and its associated subscription and origin were
+				 * dropped after updating the row, or if the origin was
+				 * manually dropped by the user.
 				 */
 				else
 					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
@@ -221,7 +222,7 @@ errdetail_apply_conflict(ConflictType type, EState *estate,
 				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
 								 origin_name, localxmin, timestamptz_to_str(localts));
 
-			/* The origin which modified the row has been dropped */
+			/* The origin that modified this row has been removed. */
 			else
 				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
 								 localxmin, timestamptz_to_str(localts));
@@ -229,7 +230,7 @@ errdetail_apply_conflict(ConflictType type, EState *estate,
 			break;
 
 		case CT_UPDATE_MISSING:
-			appendStringInfo(&err_detail, _("Did not find the row to be updated."));
+			appendStringInfo(&err_detail, _("Could not find the row to be updated."));
 			break;
 
 		case CT_DELETE_DIFFER:
@@ -240,7 +241,7 @@ errdetail_apply_conflict(ConflictType type, EState *estate,
 				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
 								 origin_name, localxmin, timestamptz_to_str(localts));
 
-			/* The origin which modified the row has been dropped */
+			/* The origin that modified this row has been removed. */
 			else
 				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
 								 localxmin, timestamptz_to_str(localts));
@@ -248,7 +249,7 @@ errdetail_apply_conflict(ConflictType type, EState *estate,
 			break;
 
 		case CT_DELETE_MISSING:
-			appendStringInfo(&err_detail, _("Did not find the row to be deleted."));
+			appendStringInfo(&err_detail, _("Could not find the row to be deleted."));
 			break;
 	}
 
@@ -268,12 +269,11 @@ errdetail_apply_conflict(ConflictType type, EState *estate,
 }
 
 /*
- * Helper function to build the additional details after the main DETAIL line
- * that describes the values of the conflicting key, existing local tuple,
- * remote tuple and replica identity columns.
+ * Helper function to build the additional details for conflicting key,
+ * existing local tuple, remote tuple, and replica identity columns.
  *
  * If the return value is NULL, it indicates that the current user lacks
- * permissions to view all the columns involved.
+ * permissions to view the columns involved.
  */
 static char *
 build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,

From a645b491a716a59a59a80edb28e0da53cbd996f4 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v14] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 235 +++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 453 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 118 ++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  58 +++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++
 src/tools/pgindent/typedefs.list            |   1 +
 18 files changed, 1000 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..3c279a1083 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict detected on relation "public.test": conflict=insert_exists
+DETAIL:  Key already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Key (c)=(1); existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..21a945923a 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint and logical replication
+ * tuple missing conflict error messages so only key columns of the index are
+ * checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..54e871cedb 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,88 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(estate, resultRelInfo, ERROR, type,
+								NULL, conflictslot, slot, uniqueidx, xmin,
+								origin, committs);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +585,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +603,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +678,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +696,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..0f51564aa2
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,453 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Functionality for detecting and logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for detecting and logging conflicts on
+ * the subscriber during logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "catalog/index.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "storage/lmgr.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static int	errdetail_apply_conflict(EState *estate,
+									 ResultRelInfo *relinfo,
+									 ConflictType type,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts);
+static char *build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+									   ConflictType type,
+									   TupleTableSlot *searchslot,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   Oid indexoid);
+static char *build_index_value_desc(EState *estate, Relation localrel,
+									TupleTableSlot *slot, Oid indexoid);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * This function is used to report a conflict while applying replication
+ * changes.
+ *
+ * 'searchslot' should contain the tuple used to search the local tuple to be
+ * updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
+ * transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * The 'indexoid' represents the OID of the replica identity index or the OID
+ * of the unique index that triggered the constraint violation error. We use
+ * this to report the key values for conflicting tuple.
+ *
+ * Note that while other indexes may also be used (see
+ * IsIndexUsableForReplicaIdentityFull for details) to find the tuple when
+ * applying update or delete, such an index scan may not result in a unique
+ * tuple and we still compare the complete tuple in such cases, thus such index
+ * OIDs should not be passed here.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can display the conflicting key value.
+ */
+void
+ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
+					ConflictType type, TupleTableSlot *searchslot,
+					TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	Assert(!OidIsValid(indexoid) ||
+		   CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	ereport(elevel,
+			errcode(ERRCODE_INTEGRITY_CONSTRAINT_VIOLATION),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(estate, relinfo, type, searchslot,
+									 localslot, remoteslot, indexoid,
+									 localxmin, localorigin, localts));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises of two parts:
+ * 1. Explanation of the conflict type, including the origin and commit
+ *    timestamp of the existing local tuple.
+ * 2. Display of conflicting key, existing local tuple, remote new tuple, and
+ *    replica identity columns, if any. The remote old tuple is excluded as its
+ *    information is covered in the replica identity columns.
+ */
+static int
+errdetail_apply_conflict(EState *estate, ResultRelInfo *relinfo,
+						 ConflictType type, TupleTableSlot *searchslot,
+						 TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts)
+{
+	StringInfoData err_detail;
+	char	   *val_desc;
+	char	   *origin_name;
+
+	initStringInfo(&err_detail);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			if (localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified locally in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by origin \"%s\" in transaction %u at %s."),
+									 get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin that modified this row has been removed. This
+				 * can happen if the origin was created by a different apply
+				 * worker and its associated subscription and origin were
+				 * dropped after updating the row, or if the origin was
+				 * manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified in transaction %u."),
+								 get_rel_name(indexoid), localxmin);
+
+			break;
+
+		case CT_UPDATE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_UPDATE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be updated."));
+			break;
+
+		case CT_DELETE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Deleting the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_DELETE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be deleted."));
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(estate, relinfo, type, searchslot,
+										 localslot, remoteslot, indexoid);
+
+	/*
+	 * Next, append the key values, existing local tuple, remote tuple and
+	 * replica identity columns after the message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * Helper function to build the additional details for conflicting key,
+ * existing local tuple, remote tuple, and replica identity columns.
+ *
+ * If the return value is NULL, it indicates that the current user lacks
+ * permissions to view the columns involved.
+ */
+static char *
+build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+						  ConflictType type,
+						  TupleTableSlot *searchslot,
+						  TupleTableSlot *localslot,
+						  TupleTableSlot *remoteslot,
+						  Oid indexoid)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	StringInfoData tuple_value;
+	char	   *desc = NULL;
+
+	Assert(searchslot || localslot || remoteslot);
+
+	initStringInfo(&tuple_value);
+
+	/*
+	 * Report the conflicting key values in the case of a unique constraint
+	 * violation.
+	 */
+	if (type == CT_INSERT_EXISTS || type == CT_UPDATE_EXISTS)
+	{
+		Assert(OidIsValid(indexoid) && localslot);
+
+		desc = build_index_value_desc(estate, localrel, localslot, indexoid);
+
+		if (desc)
+			appendStringInfo(&tuple_value, _("Key %s"), desc);
+	}
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies to the new tuple, hence we pass
+		 * NULL for the existing local tuple.
+		 */
+		desc = ExecBuildSlotValueDescription(relid, localslot, tupdesc,
+											 NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("existing local tuple %s"),
+								 desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Existing local tuple %s"),
+								 desc);
+			}
+		}
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		desc = ExecBuildSlotValueDescription(relid, remoteslot, tupdesc,
+											 modifiedCols, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("remote tuple %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Remote tuple %s"), desc);
+			}
+		}
+	}
+
+	if (searchslot)
+	{
+		/*
+		 * If a valid index OID is provided, build the replica identity key
+		 * value string. Otherwise, construct the full tuple value for REPLICA
+		 * IDENTITY FULL cases.
+		 */
+		if (OidIsValid(indexoid))
+			desc = build_index_value_desc(estate, localrel, searchslot, indexoid);
+		else
+			desc = ExecBuildSlotValueDescription(relid, searchslot, tupdesc, NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("replica identity %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Replica identity %s"), desc);
+			}
+		}
+	}
+
+	if (tuple_value.len == 0)
+		return NULL;
+
+	appendStringInfoChar(&tuple_value, '.');
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller should ensure that the index with the OID 'indexoid' is locked.
+ */
+static char *
+build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
+					   Oid indexoid)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	Assert(CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6dc54c7283..eec8c8a292 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,13 +2648,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2661,6 +2662,29 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_DIFFER,
+								remoteslot, localslot, newslot,
+								GetRelationIdentityOrPK(localrel),
+								localxmin, localorigin, localts);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2692,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2675,16 +2701,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_MISSING,
+							remoteslot, NULL, newslot,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2836,21 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_DIFFER,
+								remoteslot, localslot, NULL,
+								GetRelationIdentityOrPK(localrel), localxmin,
+								localorigin, localts);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2862,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_MISSING,
+							remoteslot, NULL, NULL,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2992,6 +3034,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3000,19 +3045,44 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(estate, partrelinfo,
+										LOG, CT_UPDATE_MISSING,
+										remoteslot_part, NULL, newslot,
+										GetRelationIdentityOrPK(partrel),
+										InvalidTransactionId,
+										InvalidRepOriginId, 0);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(estate, partrelinfo, LOG, CT_UPDATE_DIFFER,
+										remoteslot_part, localslot, newslot,
+										GetRelationIdentityOrPK(partrel),
+										localxmin, localorigin, localts);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3023,7 +3093,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3040,6 +3109,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3087,6 +3159,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..971dfa98dc
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflict detection and log
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could be encountered when applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve rules
+	 * that are more complex than simple equality checks. These conflicts are
+	 * left for future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(EState *estate, ResultRelInfo *relinfo,
+								int elevel, ConflictType type,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								Oid indexoid, TransactionId localxmin,
+								RepOriginId localorigin, TimestampTz localts);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..b4c9befa3a 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(1, quux\); replica identity \(a\)=\(1\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(26\); replica identity \(25\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(2\)/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..cf91542ed0 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(null, 4, quux\); replica identity \(a\)=\(4\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(4\)/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(10\)/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\); replica identity \(a\)=\(5\)/,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\); replica identity \(a\)=\(3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..2f099a74f3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key already exists in unique index "tbl_pkey", modified by .*origin.* transaction \d+ at .*\n.*Key \(i\)=\(\d+\); existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..01536a13e7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\); replica identity \(a\)=\(32\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\); replica identity \(a\)=\(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 547d14b3e7..6d424c8918 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 0f51564aa2..c56814cf50 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -1,14 +1,14 @@
 /*-------------------------------------------------------------------------
  * conflict.c
- *	   Functionality for detecting and logging conflicts.
+ *	   Support routines for logging conflicts.
  *
  * Copyright (c) 2024, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
  *	  src/backend/replication/logical/conflict.c
  *
- * This file contains the code for detecting and logging conflicts on
- * the subscriber during logical replication.
+ * This file contains the code for logging conflicts on the subscriber during
+ * logical replication.
  *-------------------------------------------------------------------------
  */
 
@@ -105,7 +105,7 @@ GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
  * OIDs should not be passed here.
  *
  * The caller must ensure that the index with the OID 'indexoid' is locked so
- * that we can display the conflicting key value.
+ * that we can fetch and display the conflicting key value.
  */
 void
 ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
@@ -403,7 +403,8 @@ build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
  * Helper functions to construct a string describing the contents of an index
  * entry. See BuildIndexValueDescription for details.
  *
- * The caller should ensure that the index with the OID 'indexoid' is locked.
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
  */
 static char *
 build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 971dfa98dc..02cb84da7e 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -1,6 +1,6 @@
 /*-------------------------------------------------------------------------
  * conflict.h
- *	   Exports for conflict detection and log
+ *	   Exports for conflicts logging.
  *
  * Copyright (c) 2024, PostgreSQL Global Development Group
  *
@@ -13,7 +13,7 @@
 #include "utils/timestamp.h"
 
 /*
- * Conflict types that could be encountered when applying remote changes.
+ * Conflict types that could occur while applying remote changes.
  */
 typedef enum
 {
@@ -36,9 +36,9 @@ typedef enum
 	CT_DELETE_MISSING,
 
 	/*
-	 * Other conflicts, such as exclusion constraint violations, involve rules
-	 * that are more complex than simple equality checks. These conflicts are
-	 * left for future improvements.
+	 * Other conflicts, such as exclusion constraint violations, involve more
+	 * complex rules than simple equality checks. These conflicts are left for
+	 * future improvements.
 	 */
 } ConflictType;
 

From 71d5fdad1b181689aa7f42bef4f845fa5d3d46df Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v15] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 235 +++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 482 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 118 ++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  58 +++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++
 src/tools/pgindent/typedefs.list            |   1 +
 18 files changed, 1029 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..885a2d70ae 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict detected on relation "public.test": conflict=insert_exists
+DETAIL:  Key already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Key (c)=(1); existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..21a945923a 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint and logical replication
+ * tuple missing conflict error messages so only key columns of the index are
+ * checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..54e871cedb 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,88 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *slot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, slot, &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(estate, resultRelInfo, ERROR, type,
+								NULL, conflictslot, slot, uniqueidx, xmin,
+								origin, committs);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +585,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +603,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +678,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +696,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..0baecbc8d2
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,482 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Support routines for logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for logging conflicts on the subscriber during
+ * logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "catalog/index.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "storage/lmgr.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static int	errcode_apply_conflict(ConflictType type);
+static int	errdetail_apply_conflict(EState *estate,
+									 ResultRelInfo *relinfo,
+									 ConflictType type,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts);
+static char *build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+									   ConflictType type,
+									   TupleTableSlot *searchslot,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   Oid indexoid);
+static char *build_index_value_desc(EState *estate, Relation localrel,
+									TupleTableSlot *slot, Oid indexoid);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * This function is used to report a conflict while applying replication
+ * changes.
+ *
+ * 'searchslot' should contain the tuple used to search the local tuple to be
+ * updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
+ * transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * The 'indexoid' represents the OID of the replica identity index or the OID
+ * of the unique index that triggered the constraint violation error. We use
+ * this to report the key values for conflicting tuple.
+ *
+ * Note that while other indexes may also be used (see
+ * IsIndexUsableForReplicaIdentityFull for details) to find the tuple when
+ * applying update or delete, such an index scan may not result in a unique
+ * tuple and we still compare the complete tuple in such cases, thus such index
+ * OIDs should not be passed here.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+void
+ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
+					ConflictType type, TupleTableSlot *searchslot,
+					TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	Assert(!OidIsValid(indexoid) ||
+		   CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	ereport(elevel,
+			errcode_apply_conflict(type),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(estate, relinfo, type, searchslot,
+									 localslot, remoteslot, indexoid,
+									 localxmin, localorigin, localts));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add SQLSTATE error code to the current conflict report.
+ */
+static int
+errcode_apply_conflict(ConflictType type)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			return errcode(ERRCODE_UNIQUE_VIOLATION);
+		case CT_UPDATE_DIFFER:
+		case CT_UPDATE_MISSING:
+		case CT_DELETE_DIFFER:
+		case CT_DELETE_MISSING:
+			return errcode(ERRCODE_T_R_SERIALIZATION_FAILURE);
+	}
+
+	Assert(false);
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises of two parts:
+ * 1. Explanation of the conflict type, including the origin and commit
+ *    timestamp of the existing local tuple.
+ * 2. Display of conflicting key, existing local tuple, remote new tuple, and
+ *    replica identity columns, if any. The remote old tuple is excluded as its
+ *    information is covered in the replica identity columns.
+ */
+static int
+errdetail_apply_conflict(EState *estate, ResultRelInfo *relinfo,
+						 ConflictType type, TupleTableSlot *searchslot,
+						 TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts)
+{
+	StringInfoData err_detail;
+	char	   *val_desc;
+	char	   *origin_name;
+
+	initStringInfo(&err_detail);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			if (localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified locally in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by origin \"%s\" in transaction %u at %s."),
+									 get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin that modified this row has been removed. This
+				 * can happen if the origin was created by a different apply
+				 * worker and its associated subscription and origin were
+				 * dropped after updating the row, or if the origin was
+				 * manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified in transaction %u."),
+								 get_rel_name(indexoid), localxmin);
+
+			break;
+
+		case CT_UPDATE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_UPDATE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be updated."));
+			break;
+
+		case CT_DELETE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Deleting the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_DELETE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be deleted."));
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(estate, relinfo, type, searchslot,
+										 localslot, remoteslot, indexoid);
+
+	/*
+	 * Next, append the key values, existing local tuple, remote tuple and
+	 * replica identity columns after the message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * Helper function to build the additional details for conflicting key,
+ * existing local tuple, remote tuple, and replica identity columns.
+ *
+ * If the return value is NULL, it indicates that the current user lacks
+ * permissions to view the columns involved.
+ */
+static char *
+build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+						  ConflictType type,
+						  TupleTableSlot *searchslot,
+						  TupleTableSlot *localslot,
+						  TupleTableSlot *remoteslot,
+						  Oid indexoid)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	StringInfoData tuple_value;
+	char	   *desc = NULL;
+
+	Assert(searchslot || localslot || remoteslot);
+
+	initStringInfo(&tuple_value);
+
+	/*
+	 * Report the conflicting key values in the case of a unique constraint
+	 * violation.
+	 */
+	if (type == CT_INSERT_EXISTS || type == CT_UPDATE_EXISTS)
+	{
+		Assert(OidIsValid(indexoid) && localslot);
+
+		desc = build_index_value_desc(estate, localrel, localslot, indexoid);
+
+		if (desc)
+			appendStringInfo(&tuple_value, _("Key %s"), desc);
+	}
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies to the new tuple, hence we pass
+		 * NULL for the existing local tuple.
+		 */
+		desc = ExecBuildSlotValueDescription(relid, localslot, tupdesc,
+											 NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("existing local tuple %s"),
+								 desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Existing local tuple %s"),
+								 desc);
+			}
+		}
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 *
+		 * Generated columns are not considered here because they are
+		 * generated locally on the subscriber.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		desc = ExecBuildSlotValueDescription(relid, remoteslot, tupdesc,
+											 modifiedCols, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("remote tuple %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Remote tuple %s"), desc);
+			}
+		}
+	}
+
+	if (searchslot)
+	{
+		Assert(type != CT_INSERT_EXISTS && type != CT_UPDATE_EXISTS);
+
+		/*
+		 * If a valid index OID is provided, build the replica identity key
+		 * value string. Otherwise, construct the full tuple value for REPLICA
+		 * IDENTITY FULL cases.
+		 */
+		if (OidIsValid(indexoid))
+			desc = build_index_value_desc(estate, localrel, searchslot, indexoid);
+		else
+			desc = ExecBuildSlotValueDescription(relid, searchslot, tupdesc, NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("replica identity %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Replica identity %s"), desc);
+			}
+		}
+	}
+
+	if (tuple_value.len == 0)
+		return NULL;
+
+	appendStringInfoChar(&tuple_value, '.');
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+static char *
+build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
+					   Oid indexoid)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	Assert(CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6dc54c7283..eec8c8a292 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2458,7 +2459,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2646,13 +2648,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2661,6 +2662,29 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_DIFFER,
+								remoteslot, localslot, newslot,
+								GetRelationIdentityOrPK(localrel),
+								localxmin, localorigin, localts);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2668,6 +2692,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2675,16 +2701,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_MISSING,
+							remoteslot, NULL, newslot,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2807,6 +2836,21 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_DIFFER,
+								remoteslot, localslot, NULL,
+								GetRelationIdentityOrPK(localrel), localxmin,
+								localorigin, localts);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2818,13 +2862,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_MISSING,
+							remoteslot, NULL, NULL,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2992,6 +3034,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3000,19 +3045,44 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(estate, partrelinfo,
+										LOG, CT_UPDATE_MISSING,
+										remoteslot_part, NULL, newslot,
+										GetRelationIdentityOrPK(partrel),
+										InvalidTransactionId,
+										InvalidRepOriginId, 0);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(estate, partrelinfo, LOG, CT_UPDATE_DIFFER,
+										remoteslot_part, localslot, newslot,
+										GetRelationIdentityOrPK(partrel),
+										localxmin, localorigin, localts);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3023,7 +3093,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3040,6 +3109,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3087,6 +3159,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..02cb84da7e
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflicts logging.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could occur while applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve more
+	 * complex rules than simple equality checks. These conflicts are left for
+	 * future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(EState *estate, ResultRelInfo *relinfo,
+								int elevel, ConflictType type,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								Oid indexoid, TransactionId localxmin,
+								RepOriginId localorigin, TimestampTz localts);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..b4c9befa3a 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(1, quux\); replica identity \(a\)=\(1\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(26\); replica identity \(25\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(2\)/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..cf91542ed0 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(null, 4, quux\); replica identity \(a\)=\(4\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(4\)/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(10\)/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\); replica identity \(a\)=\(5\)/,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\); replica identity \(a\)=\(3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..2f099a74f3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key already exists in unique index "tbl_pkey", modified by .*origin.* transaction \d+ at .*\n.*Key \(i\)=\(\d+\); existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..01536a13e7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\); replica identity \(a\)=\(32\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\); replica identity \(a\)=\(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 8de9978ad8..b0878d9ca8 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.31.1

From 42c46a54f9eaea4542381475f7af129d269b4899 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v16] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 236 +++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 486 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 118 ++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  58 +++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++
 src/tools/pgindent/typedefs.list            |   1 +
 18 files changed, 1034 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..885a2d70ae 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict detected on relation "public.test": conflict=insert_exists
+DETAIL:  Key already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Key (c)=(1); existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..934d180dca 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint and logical replication
+ * conflict error messages so only key columns of the index are
+ * checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..ee8d5e72d3 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,89 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'slot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *searchslot, TupleTableSlot *remoteslot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, remoteslot,
+							  &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(estate, resultRelInfo, ERROR, type,
+								searchslot, conflictslot, remoteslot,
+								uniqueidx, xmin, origin, committs);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +586,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +604,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, NULL, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +679,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +697,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, searchslot, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..55a7558403
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,486 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Support routines for logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for logging conflicts on the subscriber during
+ * logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "catalog/index.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "storage/lmgr.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static int	errcode_apply_conflict(ConflictType type);
+static int	errdetail_apply_conflict(EState *estate,
+									 ResultRelInfo *relinfo,
+									 ConflictType type,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts);
+static char *build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+									   ConflictType type,
+									   TupleTableSlot *searchslot,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   Oid indexoid);
+static char *build_index_value_desc(EState *estate, Relation localrel,
+									TupleTableSlot *slot, Oid indexoid);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * This function is used to report a conflict while applying replication
+ * changes.
+ *
+ * 'searchslot' should contain the tuple used to search the local tuple to be
+ * updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
+ * transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * The 'indexoid' represents the OID of the replica identity index or the OID
+ * of the unique index that triggered the constraint violation error. We use
+ * this to report the key values for conflicting tuple.
+ *
+ * Note that while other indexes may also be used (see
+ * IsIndexUsableForReplicaIdentityFull for details) to find the tuple when
+ * applying update or delete, such an index scan may not result in a unique
+ * tuple and we still compare the complete tuple in such cases, thus such index
+ * OIDs should not be passed here.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+void
+ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
+					ConflictType type, TupleTableSlot *searchslot,
+					TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	Assert(!OidIsValid(indexoid) ||
+		   CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	ereport(elevel,
+			errcode_apply_conflict(type),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(estate, relinfo, type, searchslot,
+									 localslot, remoteslot, indexoid,
+									 localxmin, localorigin, localts));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add SQLSTATE error code to the current conflict report.
+ */
+static int
+errcode_apply_conflict(ConflictType type)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			return errcode(ERRCODE_UNIQUE_VIOLATION);
+		case CT_UPDATE_DIFFER:
+		case CT_UPDATE_MISSING:
+		case CT_DELETE_DIFFER:
+		case CT_DELETE_MISSING:
+			return errcode(ERRCODE_T_R_SERIALIZATION_FAILURE);
+	}
+
+	Assert(false);
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises of two parts:
+ * 1. Explanation of the conflict type, including the origin and commit
+ *    timestamp of the existing local tuple.
+ * 2. Display of conflicting key, existing local tuple, remote new tuple, and
+ *    replica identity columns, if any. The remote old tuple is excluded as its
+ *    information is covered in the replica identity columns.
+ */
+static int
+errdetail_apply_conflict(EState *estate, ResultRelInfo *relinfo,
+						 ConflictType type, TupleTableSlot *searchslot,
+						 TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts)
+{
+	StringInfoData err_detail;
+	char	   *val_desc;
+	char	   *origin_name;
+
+	initStringInfo(&err_detail);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			if (localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified locally in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by origin \"%s\" in transaction %u at %s."),
+									 get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin that modified this row has been removed. This
+				 * can happen if the origin was created by a different apply
+				 * worker and its associated subscription and origin were
+				 * dropped after updating the row, or if the origin was
+				 * manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified in transaction %u."),
+								 get_rel_name(indexoid), localxmin);
+
+			break;
+
+		case CT_UPDATE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_UPDATE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be updated."));
+			break;
+
+		case CT_DELETE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Deleting the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_DELETE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be deleted."));
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(estate, relinfo, type, searchslot,
+										 localslot, remoteslot, indexoid);
+
+	/*
+	 * Next, append the key values, existing local tuple, remote tuple and
+	 * replica identity columns after the message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * Helper function to build the additional details for conflicting key,
+ * existing local tuple, remote tuple, and replica identity columns.
+ *
+ * If the return value is NULL, it indicates that the current user lacks
+ * permissions to view the columns involved.
+ */
+static char *
+build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+						  ConflictType type,
+						  TupleTableSlot *searchslot,
+						  TupleTableSlot *localslot,
+						  TupleTableSlot *remoteslot,
+						  Oid indexoid)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	StringInfoData tuple_value;
+	char	   *desc = NULL;
+
+	Assert(searchslot || localslot || remoteslot);
+
+	initStringInfo(&tuple_value);
+
+	/*
+	 * Report the conflicting key values in the case of a unique constraint
+	 * violation.
+	 */
+	if (type == CT_INSERT_EXISTS || type == CT_UPDATE_EXISTS)
+	{
+		Assert(OidIsValid(indexoid) && localslot);
+
+		desc = build_index_value_desc(estate, localrel, localslot, indexoid);
+
+		if (desc)
+			appendStringInfo(&tuple_value, _("Key %s"), desc);
+	}
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies to the new tuple, hence we pass
+		 * NULL for the existing local tuple.
+		 */
+		desc = ExecBuildSlotValueDescription(relid, localslot, tupdesc,
+											 NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("existing local tuple %s"),
+								 desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Existing local tuple %s"),
+								 desc);
+			}
+		}
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 *
+		 * Generated columns are not considered here because they are
+		 * generated locally on the subscriber.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		desc = ExecBuildSlotValueDescription(relid, remoteslot, tupdesc,
+											 modifiedCols, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("remote tuple %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Remote tuple %s"), desc);
+			}
+		}
+	}
+
+	if (searchslot)
+	{
+		Assert(type != CT_INSERT_EXISTS);
+
+		/*
+		 * If a valid index OID is provided, build the replica identity key
+		 * value string. Otherwise, construct the full tuple value for REPLICA
+		 * IDENTITY FULL cases.
+		 */
+		if (OidIsValid(indexoid))
+			desc = build_index_value_desc(estate, localrel, searchslot, indexoid);
+		else
+			desc = ExecBuildSlotValueDescription(relid, searchslot, tupdesc, NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, OidIsValid(indexoid)
+								 ? _("replica identity %s")
+								 : _("replica identity full %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, OidIsValid(indexoid)
+								 ? _("Replica identity %s")
+								 : _("Replica identity full %s"), desc);
+			}
+		}
+	}
+
+	if (tuple_value.len == 0)
+		return NULL;
+
+	appendStringInfoChar(&tuple_value, '.');
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+static char *
+build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
+					   Oid indexoid)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	Assert(CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 245e9be6f2..39fc062881 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2481,7 +2482,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2669,13 +2671,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2684,6 +2685,29 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_DIFFER,
+								remoteslot, localslot, newslot,
+								GetRelationIdentityOrPK(localrel),
+								localxmin, localorigin, localts);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2691,6 +2715,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2698,16 +2724,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_MISSING,
+							remoteslot, NULL, newslot,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2830,6 +2859,21 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_DIFFER,
+								remoteslot, localslot, NULL,
+								GetRelationIdentityOrPK(localrel), localxmin,
+								localorigin, localts);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2841,13 +2885,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_MISSING,
+							remoteslot, NULL, NULL,
+							GetRelationIdentityOrPK(localrel),
+							InvalidTransactionId, InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -3015,6 +3057,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3023,19 +3068,44 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(estate, partrelinfo,
+										LOG, CT_UPDATE_MISSING,
+										remoteslot_part, NULL, newslot,
+										GetRelationIdentityOrPK(partrel),
+										InvalidTransactionId,
+										InvalidRepOriginId, 0);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(estate, partrelinfo, LOG, CT_UPDATE_DIFFER,
+										remoteslot_part, localslot, newslot,
+										GetRelationIdentityOrPK(partrel),
+										localxmin, localorigin, localts);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3046,7 +3116,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3063,6 +3132,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3110,6 +3182,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..02cb84da7e
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflicts logging.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could occur while applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve more
+	 * complex rules than simple equality checks. These conflicts are left for
+	 * future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(EState *estate, ResultRelInfo *relinfo,
+								int elevel, ConflictType type,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								Oid indexoid, TransactionId localxmin,
+								RepOriginId localorigin, TimestampTz localts);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..d377e7ae2b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(1, quux\); replica identity \(a\)=\(1\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(26\); replica identity full \(25\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(2\)/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..cf91542ed0 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(null, 4, quux\); replica identity \(a\)=\(4\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(4\)/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(10\)/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\); replica identity \(a\)=\(5\)/,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\); replica identity \(a\)=\(3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..2f099a74f3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key already exists in unique index "tbl_pkey", modified by .*origin.* transaction \d+ at .*\n.*Key \(i\)=\(\d+\); existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..01536a13e7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\); replica identity \(a\)=\(32\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\); replica identity \(a\)=\(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 547d14b3e7..6d424c8918 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From c4901b60d58abac922a3606839f216a2c4c052ba Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v17] Detect and log conflicts in logical replication

This patch enables the logical replication worker to provide additional logging
information in the following conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled.

We do not offer additional logging for exclusion constraints violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts may not be straightforward. Therefore, we
leave this area for future improvements.
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 236 +++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 489 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 115 ++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  58 +++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++
 src/tools/pgindent/typedefs.list            |   1 +
 18 files changed, 1034 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..885a2d70ae 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict detected on relation "public.test": conflict=insert_exists
+DETAIL:  Key already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Key (c)=(1); existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..347e295a52 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint error messages and
+ * logical replication conflict error messages so only key columns of the index
+ * are checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..1086cbc962 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,89 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'remoteslot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *searchslot, TupleTableSlot *remoteslot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, remoteslot,
+							  &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(estate, resultRelInfo, ERROR, type,
+								searchslot, conflictslot, remoteslot,
+								uniqueidx, xmin, origin, committs);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +586,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +604,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, NULL, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +679,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +697,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, searchslot, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..6c3c8b25e9
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,489 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Support routines for logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for logging conflicts on the subscriber during
+ * logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "catalog/index.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "replication/logicalrelation.h"
+#include "storage/lmgr.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static int	errcode_apply_conflict(ConflictType type);
+static int	errdetail_apply_conflict(EState *estate,
+									 ResultRelInfo *relinfo,
+									 ConflictType type,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts);
+static char *build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+									   ConflictType type,
+									   TupleTableSlot *searchslot,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   Oid indexoid);
+static char *build_index_value_desc(EState *estate, Relation localrel,
+									TupleTableSlot *slot, Oid indexoid);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * This function is used to report a conflict while applying replication
+ * changes.
+ *
+ * 'searchslot' should contain the tuple used to search the local tuple to be
+ * updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
+ * transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * The 'indexoid' represents the OID of the unique index that triggered the
+ * constraint violation error. We use this to report the key values for
+ * conflicting tuple.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+void
+ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
+					ConflictType type, TupleTableSlot *searchslot,
+					TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	Assert(!OidIsValid(indexoid) ||
+		   CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	ereport(elevel,
+			errcode_apply_conflict(type),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(estate, relinfo, type, searchslot,
+									 localslot, remoteslot, indexoid,
+									 localxmin, localorigin, localts));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add SQLSTATE error code to the current conflict report.
+ */
+static int
+errcode_apply_conflict(ConflictType type)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			return errcode(ERRCODE_UNIQUE_VIOLATION);
+		case CT_UPDATE_DIFFER:
+		case CT_UPDATE_MISSING:
+		case CT_DELETE_DIFFER:
+		case CT_DELETE_MISSING:
+			return errcode(ERRCODE_T_R_SERIALIZATION_FAILURE);
+	}
+
+	Assert(false);
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises of two parts:
+ * 1. Explanation of the conflict type, including the origin and commit
+ *    timestamp of the existing local tuple.
+ * 2. Display of conflicting key, existing local tuple, remote new tuple, and
+ *    replica identity columns, if any. The remote old tuple is excluded as its
+ *    information is covered in the replica identity columns.
+ */
+static int
+errdetail_apply_conflict(EState *estate, ResultRelInfo *relinfo,
+						 ConflictType type, TupleTableSlot *searchslot,
+						 TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts)
+{
+	StringInfoData err_detail;
+	char	   *val_desc;
+	char	   *origin_name;
+
+	initStringInfo(&err_detail);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			if (localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified locally in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by origin \"%s\" in transaction %u at %s."),
+									 get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin that modified this row has been removed. This
+				 * can happen if the origin was created by a different apply
+				 * worker and its associated subscription and origin were
+				 * dropped after updating the row, or if the origin was
+				 * manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified in transaction %u."),
+								 get_rel_name(indexoid), localxmin);
+
+			break;
+
+		case CT_UPDATE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_UPDATE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be updated."));
+			break;
+
+		case CT_DELETE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Deleting the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_DELETE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be deleted."));
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(estate, relinfo, type, searchslot,
+										 localslot, remoteslot, indexoid);
+
+	/*
+	 * Next, append the key values, existing local tuple, remote tuple and
+	 * replica identity columns after the message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * Helper function to build the additional details for conflicting key,
+ * existing local tuple, remote tuple, and replica identity columns.
+ *
+ * If the return value is NULL, it indicates that the current user lacks
+ * permissions to view the columns involved.
+ */
+static char *
+build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+						  ConflictType type,
+						  TupleTableSlot *searchslot,
+						  TupleTableSlot *localslot,
+						  TupleTableSlot *remoteslot,
+						  Oid indexoid)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	StringInfoData tuple_value;
+	char	   *desc = NULL;
+
+	Assert(searchslot || localslot || remoteslot);
+
+	initStringInfo(&tuple_value);
+
+	/*
+	 * Report the conflicting key values in the case of a unique constraint
+	 * violation.
+	 */
+	if (type == CT_INSERT_EXISTS || type == CT_UPDATE_EXISTS)
+	{
+		Assert(OidIsValid(indexoid) && localslot);
+
+		desc = build_index_value_desc(estate, localrel, localslot, indexoid);
+
+		if (desc)
+			appendStringInfo(&tuple_value, _("Key %s"), desc);
+	}
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies to the new tuple, hence we pass
+		 * NULL for the existing local tuple.
+		 */
+		desc = ExecBuildSlotValueDescription(relid, localslot, tupdesc,
+											 NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("existing local tuple %s"),
+								 desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Existing local tuple %s"),
+								 desc);
+			}
+		}
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 *
+		 * Note that generated columns are formed locally on the subscriber.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		desc = ExecBuildSlotValueDescription(relid, remoteslot, tupdesc,
+											 modifiedCols, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("remote tuple %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Remote tuple %s"), desc);
+			}
+		}
+	}
+
+	if (searchslot)
+	{
+		/*
+		 * Get the replica identity index. Note that while other indexes may
+		 * also be used (see IsIndexUsableForReplicaIdentityFull for details)
+		 * to find the tuple when applying update or delete, such an index
+		 * scan may not result in a unique tuple and we still compare the
+		 * complete tuple in such cases, thus such indexes are not used here.
+		 */
+		Oid			replica_index = GetRelationIdentityOrPK(localrel);
+
+		Assert(type != CT_INSERT_EXISTS);
+
+		/*
+		 * If the table has a valid replica identity index, build the index
+		 * key value string. Otherwise, construct the full tuple value for
+		 * REPLICA IDENTITY FULL cases.
+		 */
+		if (OidIsValid(replica_index))
+			desc = build_index_value_desc(estate, localrel, searchslot, replica_index);
+		else
+			desc = ExecBuildSlotValueDescription(relid, searchslot, tupdesc, NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, OidIsValid(replica_index)
+								 ? _("replica identity %s")
+								 : _("replica identity full %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, OidIsValid(replica_index)
+								 ? _("Replica identity %s")
+								 : _("Replica identity full %s"), desc);
+			}
+		}
+	}
+
+	if (tuple_value.len == 0)
+		return NULL;
+
+	appendStringInfoChar(&tuple_value, '.');
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+static char *
+build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
+					   Oid indexoid)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	Assert(CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 245e9be6f2..cdea6295d8 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2481,7 +2482,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2669,13 +2671,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2684,6 +2685,28 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_DIFFER,
+								remoteslot, localslot, newslot,
+								InvalidOid, localxmin, localorigin, localts);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2691,6 +2714,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2698,16 +2723,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_MISSING,
+							remoteslot, NULL, newslot,
+							InvalidOid, InvalidTransactionId,
+							InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2830,6 +2858,20 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_DIFFER,
+								remoteslot, localslot, NULL,
+								InvalidOid, localxmin, localorigin, localts);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2841,13 +2883,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_MISSING,
+							remoteslot, NULL, NULL,
+							InvalidOid, InvalidTransactionId,
+							InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -3015,6 +3055,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3023,19 +3066,43 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(estate, partrelinfo,
+										LOG, CT_UPDATE_MISSING,
+										remoteslot_part, NULL, newslot,
+										InvalidOid, InvalidTransactionId,
+										InvalidRepOriginId, 0);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(estate, partrelinfo, LOG, CT_UPDATE_DIFFER,
+										remoteslot_part, localslot, newslot,
+										InvalidOid, localxmin, localorigin,
+										localts);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3046,7 +3113,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3063,6 +3129,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3110,6 +3179,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..02cb84da7e
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflicts logging.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could occur while applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve more
+	 * complex rules than simple equality checks. These conflicts are left for
+	 * future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(EState *estate, ResultRelInfo *relinfo,
+								int elevel, ConflictType type,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								Oid indexoid, TransactionId localxmin,
+								RepOriginId localorigin, TimestampTz localts);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..d377e7ae2b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(1, quux\); replica identity \(a\)=\(1\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(26\); replica identity full \(25\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(2\)/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..cf91542ed0 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(null, 4, quux\); replica identity \(a\)=\(4\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(4\)/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(10\)/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\); replica identity \(a\)=\(5\)/,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\); replica identity \(a\)=\(3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..2f099a74f3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key already exists in unique index "tbl_pkey", modified by .*origin.* transaction \d+ at .*\n.*Key \(i\)=\(\d+\); existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..01536a13e7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\); replica identity \(a\)=\(32\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\); replica identity \(a\)=\(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 547d14b3e7..6d424c8918 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.30.0.windows.2

From b5d9ef840c78d5897aaf00a202146b9b38884851 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Thu, 1 Aug 2024 13:36:22 +0800
Subject: [PATCH v18] Log the conflicts while applying changes in logical
 replication.

This patch provides the additional logging information in the following
conflict scenarios while applying changes:

insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.

For insert_exists and update_exists conflicts, the log can include the origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.

update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled on the subscriber.

We do not offer additional logging for exclusion constraint violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts won't be straightforward. This area can be
further enhanced if required.

Author: Hou Zhijie
Reviewed-by: Shveta Malik, Amit Kapila, Hayato Kuroda, Dilip Kumar
Discussion: https://postgr.es/m/OS0PR01MB5716352552DFADB8E9AD1D8994C92@OS0PR01MB5716.jpnprd01.prod.outlook.com
---
 doc/src/sgml/logical-replication.sgml       | 103 ++++-
 src/backend/access/index/genam.c            |   5 +-
 src/backend/catalog/index.c                 |   5 +-
 src/backend/executor/execIndexing.c         |  17 +-
 src/backend/executor/execMain.c             |   7 +-
 src/backend/executor/execReplication.c      | 236 +++++++---
 src/backend/executor/nodeModifyTable.c      |   5 +-
 src/backend/replication/logical/Makefile    |   1 +
 src/backend/replication/logical/conflict.c  | 488 ++++++++++++++++++++
 src/backend/replication/logical/meson.build |   1 +
 src/backend/replication/logical/worker.c    | 115 ++++-
 src/include/executor/executor.h             |   5 +
 src/include/replication/conflict.h          |  58 +++
 src/test/subscription/t/001_rep_changes.pl  |  18 +-
 src/test/subscription/t/013_partition.pl    |  53 +--
 src/test/subscription/t/029_on_error.pl     |  11 +-
 src/test/subscription/t/030_origin.pl       |  47 ++
 src/tools/pgindent/typedefs.list            |   1 +
 18 files changed, 1033 insertions(+), 143 deletions(-)
 create mode 100644 src/backend/replication/logical/conflict.c
 create mode 100644 src/include/replication/conflict.h

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index a23a3d57e2..885a2d70ae 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1579,8 +1579,91 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    node.  If incoming data violates any constraints the replication will
    stop.  This is referred to as a <firstterm>conflict</firstterm>.  When
    replicating <command>UPDATE</command> or <command>DELETE</command>
-   operations, missing data will not produce a conflict and such operations
-   will simply be skipped.
+   operations, missing data is also considered as a
+   <firstterm>conflict</firstterm>, but does not result in an error and such
+   operations will simply be skipped.
+  </para>
+
+  <para>
+   Additional logging is triggered in the following <firstterm>conflict</firstterm>
+   cases:
+   <variablelist>
+    <varlistentry>
+     <term><literal>insert_exists</literal></term>
+     <listitem>
+      <para>
+       Inserting a row that violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_differ</literal></term>
+     <listitem>
+      <para>
+       Updating a row that was previously modified by another origin.
+       Note that this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the update is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_exists</literal></term>
+     <listitem>
+      <para>
+       The updated value of a row violates a <literal>NOT DEFERRABLE</literal>
+       unique constraint. Note that to log the origin and commit
+       timestamp details of the conflicting key,
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       should be enabled on the subscriber. In this case, an error will be
+       raised until the conflict is resolved manually. Note that when updating a
+       partitioned table, if the updated row value satisfies another partition
+       constraint resulting in the row being inserted into a new partition, the
+       <literal>insert_exists</literal> conflict may arise if the new row
+       violates a <literal>NOT DEFERRABLE</literal> unique constraint.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>update_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be updated was not found. The update will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_differ</literal></term>
+     <listitem>
+      <para>
+       Deleting a row that was previously modified by another origin. Note that
+       this conflict can only be detected when
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       is enabled on the subscriber. Currenly, the delete is always applied
+       regardless of the origin of the local row.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term><literal>delete_missing</literal></term>
+     <listitem>
+      <para>
+       The tuple to be deleted was not found. The delete will simply be
+       skipped in this scenario.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+    Note that there are other conflict scenarios, such as exclusion constraint
+    violations. Currently, we do not provide additional details for them in the
+    log.
   </para>
 
   <para>
@@ -1597,7 +1680,7 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   A conflict will produce an error and will stop the replication; it must be
+   A conflict that produces an error will stop the replication; it must be
    resolved manually by the user.  Details about the conflict can be found in
    the subscriber's server log.
   </para>
@@ -1609,8 +1692,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
    an error, the replication won't proceed, and the logical replication worker will
    emit the following kind of message to the subscriber's server log:
 <screen>
-ERROR:  duplicate key value violates unique constraint "test_pkey"
-DETAIL:  Key (c)=(1) already exists.
+ERROR:  conflict detected on relation "public.test": conflict=insert_exists
+DETAIL:  Key already exists in unique index "t_pkey", which was modified locally in transaction 740 at 2024-06-26 10:47:04.727375+08.
+Key (c)=(1); existing local tuple (1, 'local'); remote tuple (1, 'remote').
 CONTEXT:  processing remote data for replication origin "pg_16395" during "INSERT" for replication target relation "public.test" in transaction 725 finished at 0/14C0378
 </screen>
    The LSN of the transaction that contains the change violating the constraint and
@@ -1636,6 +1720,15 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    Please note that skipping the whole transaction includes skipping changes that
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
+   The additional details regarding conflicting rows, such as their origin and
+   commit timestamp can be seen in the <literal>DETAIL</literal> line of the
+   log. But note that this information is only available when
+   <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+   is enabled on the subscriber. Users can use this information to decide
+   whether to retain the local change or adopt the remote alteration. For
+   instance, the <literal>DETAIL</literal> line in the above log indicates that
+   the existing row was modified locally. Users can manually perform a
+   remote-change-win.
   </para>
 
   <para>
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index de751e8e4a..43c95d6109 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -154,8 +154,9 @@ IndexScanEnd(IndexScanDesc scan)
  *
  * Construct a string describing the contents of an index entry, in the
  * form "(key_name, ...)=(key_value, ...)".  This is currently used
- * for building unique-constraint and exclusion-constraint error messages,
- * so only key columns of the index are checked and printed.
+ * for building unique-constraint, exclusion-constraint error messages, and
+ * logical replication conflict error messages so only key columns of the index
+ * are checked and printed.
  *
  * Note that if the user does not have permissions to view all of the
  * columns involved then a NULL is returned.  Returning a partial key seems
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a819b4197c..33759056e3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2631,8 +2631,9 @@ CompareIndexInfo(const IndexInfo *info1, const IndexInfo *info2,
  *			Add extra state to IndexInfo record
  *
  * For unique indexes, we usually don't want to add info to the IndexInfo for
- * checking uniqueness, since the B-Tree AM handles that directly.  However,
- * in the case of speculative insertion, additional support is required.
+ * checking uniqueness, since the B-Tree AM handles that directly.  However, in
+ * the case of speculative insertion and conflict detection in logical
+ * replication, additional support is required.
  *
  * Do this processing here rather than in BuildIndexInfo() to not incur the
  * overhead in the common non-speculative cases.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 9f05b3654c..403a3f4055 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -207,8 +207,9 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
 		ii = BuildIndexInfo(indexDesc);
 
 		/*
-		 * If the indexes are to be used for speculative insertion, add extra
-		 * information required by unique index entries.
+		 * If the indexes are to be used for speculative insertion or conflict
+		 * detection in logical replication, add extra information required by
+		 * unique index entries.
 		 */
 		if (speculative && ii->ii_Unique)
 			BuildSpeculativeIndexInfo(indexDesc, ii);
@@ -519,14 +520,18 @@ ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
  *
  *		Note that this doesn't lock the values in any way, so it's
  *		possible that a conflicting tuple is inserted immediately
- *		after this returns.  But this can be used for a pre-check
- *		before insertion.
+ *		after this returns.  This can be used for either a pre-check
+ *		before insertion or a re-check after finding a conflict.
+ *
+ *		'tupleid' should be the TID of the tuple that has been recently
+ *		inserted (or can be invalid if we haven't inserted a new tuple yet).
+ *		This tuple will be excluded from conflict checking.
  * ----------------------------------------------------------------
  */
 bool
 ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 						  EState *estate, ItemPointer conflictTid,
-						  List *arbiterIndexes)
+						  ItemPointer tupleid, List *arbiterIndexes)
 {
 	int			i;
 	int			numIndices;
@@ -629,7 +634,7 @@ ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
 		satisfiesConstraint =
 			check_exclusion_or_unique_constraint(heapRelation, indexRelation,
-												 indexInfo, &invalidItemPtr,
+												 indexInfo, tupleid,
 												 values, isnull, estate, false,
 												 CEOUC_WAIT, true,
 												 conflictTid);
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7c92d63c..29e186fa73 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -88,11 +88,6 @@ static bool ExecCheckPermissionsModified(Oid relOid, Oid userid,
 										 Bitmapset *modifiedCols,
 										 AclMode requiredPerms);
 static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
-static char *ExecBuildSlotValueDescription(Oid reloid,
-										   TupleTableSlot *slot,
-										   TupleDesc tupdesc,
-										   Bitmapset *modifiedCols,
-										   int maxfieldlen);
 static void EvalPlanQualStart(EPQState *epqstate, Plan *planTree);
 
 /* end of local decls */
@@ -2210,7 +2205,7 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  * column involved, that subset will be returned with a key identifying which
  * columns they are.
  */
-static char *
+char *
 ExecBuildSlotValueDescription(Oid reloid,
 							  TupleTableSlot *slot,
 							  TupleDesc tupdesc,
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index d0a89cd577..1086cbc962 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -23,6 +23,7 @@
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/nodeModifyTable.h"
+#include "replication/conflict.h"
 #include "replication/logicalrelation.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -166,6 +167,51 @@ build_replindex_scan_key(ScanKey skey, Relation rel, Relation idxrel,
 	return skey_attoff;
 }
 
+
+/*
+ * Helper function to check if it is necessary to re-fetch and lock the tuple
+ * due to concurrent modifications. This function should be called after
+ * invoking table_tuple_lock.
+ */
+static bool
+should_refetch_tuple(TM_Result res, TM_FailureData *tmfd)
+{
+	bool		refetch = false;
+
+	switch (res)
+	{
+		case TM_Ok:
+			break;
+		case TM_Updated:
+			/* XXX: Improve handling here */
+			if (ItemPointerIndicatesMovedPartitions(&tmfd->ctid))
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
+			else
+				ereport(LOG,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("concurrent update, retrying")));
+			refetch = true;
+			break;
+		case TM_Deleted:
+			/* XXX: Improve handling here */
+			ereport(LOG,
+					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+					 errmsg("concurrent delete, retrying")));
+			refetch = true;
+			break;
+		case TM_Invisible:
+			elog(ERROR, "attempted to lock invisible tuple");
+			break;
+		default:
+			elog(ERROR, "unexpected table_tuple_lock status: %u", res);
+			break;
+	}
+
+	return refetch;
+}
+
 /*
  * Search the relation 'rel' for tuple using the index.
  *
@@ -260,34 +306,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	index_endscan(scan);
@@ -444,34 +464,8 @@ retry:
 
 		PopActiveSnapshot();
 
-		switch (res)
-		{
-			case TM_Ok:
-				break;
-			case TM_Updated:
-				/* XXX: Improve handling here */
-				if (ItemPointerIndicatesMovedPartitions(&tmfd.ctid))
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("tuple to be locked was already moved to another partition due to concurrent update, retrying")));
-				else
-					ereport(LOG,
-							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-							 errmsg("concurrent update, retrying")));
-				goto retry;
-			case TM_Deleted:
-				/* XXX: Improve handling here */
-				ereport(LOG,
-						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
-						 errmsg("concurrent delete, retrying")));
-				goto retry;
-			case TM_Invisible:
-				elog(ERROR, "attempted to lock invisible tuple");
-				break;
-			default:
-				elog(ERROR, "unexpected table_tuple_lock status: %u", res);
-				break;
-		}
+		if (should_refetch_tuple(res, &tmfd))
+			goto retry;
 	}
 
 	table_endscan(scan);
@@ -480,6 +474,89 @@ retry:
 	return found;
 }
 
+/*
+ * Find the tuple that violates the passed unique index (conflictindex).
+ *
+ * If the conflicting tuple is found return true, otherwise false.
+ *
+ * We lock the tuple to avoid getting it deleted before the caller can fetch
+ * the required information. Note that if the tuple is deleted before a lock
+ * is acquired, we will retry to find the conflicting tuple again.
+ */
+static bool
+FindConflictTuple(ResultRelInfo *resultRelInfo, EState *estate,
+				  Oid conflictindex, TupleTableSlot *slot,
+				  TupleTableSlot **conflictslot)
+{
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	ItemPointerData conflictTid;
+	TM_FailureData tmfd;
+	TM_Result	res;
+
+	*conflictslot = NULL;
+
+retry:
+	if (ExecCheckIndexConstraints(resultRelInfo, slot, estate,
+								  &conflictTid, &slot->tts_tid,
+								  list_make1_oid(conflictindex)))
+	{
+		if (*conflictslot)
+			ExecDropSingleTupleTableSlot(*conflictslot);
+
+		*conflictslot = NULL;
+		return false;
+	}
+
+	*conflictslot = table_slot_create(rel, NULL);
+
+	PushActiveSnapshot(GetLatestSnapshot());
+
+	res = table_tuple_lock(rel, &conflictTid, GetLatestSnapshot(),
+						   *conflictslot,
+						   GetCurrentCommandId(false),
+						   LockTupleShare,
+						   LockWaitBlock,
+						   0 /* don't follow updates */ ,
+						   &tmfd);
+
+	PopActiveSnapshot();
+
+	if (should_refetch_tuple(res, &tmfd))
+		goto retry;
+
+	return true;
+}
+
+/*
+ * Check all the unique indexes in 'recheckIndexes' for conflict with the
+ * tuple in 'remoteslot' and report if found.
+ */
+static void
+CheckAndReportConflict(ResultRelInfo *resultRelInfo, EState *estate,
+					   ConflictType type, List *recheckIndexes,
+					   TupleTableSlot *searchslot, TupleTableSlot *remoteslot)
+{
+	/* Check all the unique indexes for a conflict */
+	foreach_oid(uniqueidx, resultRelInfo->ri_onConflictArbiterIndexes)
+	{
+		TupleTableSlot *conflictslot;
+
+		if (list_member_oid(recheckIndexes, uniqueidx) &&
+			FindConflictTuple(resultRelInfo, estate, uniqueidx, remoteslot,
+							  &conflictslot))
+		{
+			RepOriginId origin;
+			TimestampTz committs;
+			TransactionId xmin;
+
+			GetTupleTransactionInfo(conflictslot, &xmin, &origin, &committs);
+			ReportApplyConflict(estate, resultRelInfo, ERROR, type,
+								searchslot, conflictslot, remoteslot,
+								uniqueidx, xmin, origin, committs);
+		}
+	}
+}
+
 /*
  * Insert tuple represented in the slot to the relation, update the indexes,
  * and execute any constraints and per-row triggers.
@@ -509,6 +586,8 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 	if (!skip_tuple)
 	{
 		List	   *recheckIndexes = NIL;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -525,10 +604,33 @@ ExecSimpleRelationInsert(ResultRelInfo *resultRelInfo,
 		/* OK, store the tuple and create index entries for it */
 		simple_table_tuple_insert(resultRelInfo->ri_RelationDesc, slot);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0)
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, false, false,
-												   NULL, NIL, false);
+												   slot, estate, false,
+												   conflictindexes ? true : false,
+												   &conflict,
+												   conflictindexes, false);
+
+		/*
+		 * Checks the conflict indexes to fetch the conflicting local tuple
+		 * and reports the conflict. We perform this check here, instead of
+		 * performing an additional index scan before the actual insertion and
+		 * reporting the conflict if any conflicting tuples are found. This is
+		 * to avoid the overhead of executing the extra scan for each INSERT
+		 * operation, even when no conflict arises, which could introduce
+		 * significant overhead to replication, particularly in cases where
+		 * conflicts are rare.
+		 *
+		 * XXX OTOH, this could lead to clean-up effort for dead tuples added
+		 * in heap and index in case of conflicts. But as conflicts shouldn't
+		 * be a frequent thing so we preferred to save the performance
+		 * overhead of extra scan before each insertion.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_INSERT_EXISTS,
+								   recheckIndexes, NULL, slot);
 
 		/* AFTER ROW INSERT Triggers */
 		ExecARInsertTriggers(estate, resultRelInfo, slot,
@@ -577,6 +679,8 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 	{
 		List	   *recheckIndexes = NIL;
 		TU_UpdateIndexes update_indexes;
+		List	   *conflictindexes;
+		bool		conflict = false;
 
 		/* Compute stored generated columns */
 		if (rel->rd_att->constr &&
@@ -593,12 +697,24 @@ ExecSimpleRelationUpdate(ResultRelInfo *resultRelInfo,
 		simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,
 								  &update_indexes);
 
+		conflictindexes = resultRelInfo->ri_onConflictArbiterIndexes;
+
 		if (resultRelInfo->ri_NumIndices > 0 && (update_indexes != TU_None))
 			recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
-												   slot, estate, true, false,
-												   NULL, NIL,
+												   slot, estate, true,
+												   conflictindexes ? true : false,
+												   &conflict, conflictindexes,
 												   (update_indexes == TU_Summarizing));
 
+		/*
+		 * Refer to the comments above the call to CheckAndReportConflict() in
+		 * ExecSimpleRelationInsert to understand why this check is done at
+		 * this point.
+		 */
+		if (conflict)
+			CheckAndReportConflict(resultRelInfo, estate, CT_UPDATE_EXISTS,
+								   recheckIndexes, searchslot, slot);
+
 		/* AFTER ROW UPDATE Triggers */
 		ExecARUpdateTriggers(estate, resultRelInfo,
 							 NULL, NULL,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 4913e49319..8bf4c80d4a 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1019,9 +1019,11 @@ ExecInsert(ModifyTableContext *context,
 			/* Perform a speculative insertion. */
 			uint32		specToken;
 			ItemPointerData conflictTid;
+			ItemPointerData invalidItemPtr;
 			bool		specConflict;
 			List	   *arbiterIndexes;
 
+			ItemPointerSetInvalid(&invalidItemPtr);
 			arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
 			/*
@@ -1041,7 +1043,8 @@ ExecInsert(ModifyTableContext *context,
 			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
-										   &conflictTid, arbiterIndexes))
+										   &conflictTid, &invalidItemPtr,
+										   arbiterIndexes))
 			{
 				/* committed conflict tuple found */
 				if (onconflict == ONCONFLICT_UPDATE)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index ba03eeff1c..1e08bbbd4e 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -16,6 +16,7 @@ override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
 	applyparallelworker.o \
+	conflict.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
new file mode 100644
index 0000000000..fe46e69438
--- /dev/null
+++ b/src/backend/replication/logical/conflict.c
@@ -0,0 +1,488 @@
+/*-------------------------------------------------------------------------
+ * conflict.c
+ *	   Support routines for logging conflicts.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/conflict.c
+ *
+ * This file contains the code for logging conflicts on the subscriber during
+ * logical replication.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/commit_ts.h"
+#include "access/tableam.h"
+#include "executor/executor.h"
+#include "replication/conflict.h"
+#include "replication/logicalrelation.h"
+#include "storage/lmgr.h"
+#include "utils/lsyscache.h"
+
+static const char *const ConflictTypeNames[] = {
+	[CT_INSERT_EXISTS] = "insert_exists",
+	[CT_UPDATE_DIFFER] = "update_differ",
+	[CT_UPDATE_EXISTS] = "update_exists",
+	[CT_UPDATE_MISSING] = "update_missing",
+	[CT_DELETE_DIFFER] = "delete_differ",
+	[CT_DELETE_MISSING] = "delete_missing"
+};
+
+static int	errcode_apply_conflict(ConflictType type);
+static int	errdetail_apply_conflict(EState *estate,
+									 ResultRelInfo *relinfo,
+									 ConflictType type,
+									 TupleTableSlot *searchslot,
+									 TupleTableSlot *localslot,
+									 TupleTableSlot *remoteslot,
+									 Oid indexoid, TransactionId localxmin,
+									 RepOriginId localorigin,
+									 TimestampTz localts);
+static char *build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+									   ConflictType type,
+									   TupleTableSlot *searchslot,
+									   TupleTableSlot *localslot,
+									   TupleTableSlot *remoteslot,
+									   Oid indexoid);
+static char *build_index_value_desc(EState *estate, Relation localrel,
+									TupleTableSlot *slot, Oid indexoid);
+
+/*
+ * Get the xmin and commit timestamp data (origin and timestamp) associated
+ * with the provided local tuple.
+ *
+ * Return true if the commit timestamp data was found, false otherwise.
+ */
+bool
+GetTupleTransactionInfo(TupleTableSlot *localslot, TransactionId *xmin,
+						RepOriginId *localorigin, TimestampTz *localts)
+{
+	Datum		xminDatum;
+	bool		isnull;
+
+	xminDatum = slot_getsysattr(localslot, MinTransactionIdAttributeNumber,
+								&isnull);
+	*xmin = DatumGetTransactionId(xminDatum);
+	Assert(!isnull);
+
+	/*
+	 * The commit timestamp data is not available if track_commit_timestamp is
+	 * disabled.
+	 */
+	if (!track_commit_timestamp)
+	{
+		*localorigin = InvalidRepOriginId;
+		*localts = 0;
+		return false;
+	}
+
+	return TransactionIdGetCommitTsData(*xmin, localts, localorigin);
+}
+
+/*
+ * This function is used to report a conflict while applying replication
+ * changes.
+ *
+ * 'searchslot' should contain the tuple used to search the local tuple to be
+ * updated or deleted.
+ *
+ * 'localslot' should contain the existing local tuple, if any, that conflicts
+ * with the remote tuple. 'localxmin', 'localorigin', and 'localts' provide the
+ * transaction information related to this existing local tuple.
+ *
+ * 'remoteslot' should contain the remote new tuple, if any.
+ *
+ * The 'indexoid' represents the OID of the unique index that triggered the
+ * constraint violation error. We use this to report the key values for
+ * conflicting tuple.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+void
+ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
+					ConflictType type, TupleTableSlot *searchslot,
+					TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+					Oid indexoid, TransactionId localxmin,
+					RepOriginId localorigin, TimestampTz localts)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+
+	Assert(!OidIsValid(indexoid) ||
+		   CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	ereport(elevel,
+			errcode_apply_conflict(type),
+			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
+				   get_namespace_name(RelationGetNamespace(localrel)),
+				   RelationGetRelationName(localrel),
+				   ConflictTypeNames[type]),
+			errdetail_apply_conflict(estate, relinfo, type, searchslot,
+									 localslot, remoteslot, indexoid,
+									 localxmin, localorigin, localts));
+}
+
+/*
+ * Find all unique indexes to check for a conflict and store them into
+ * ResultRelInfo.
+ */
+void
+InitConflictIndexes(ResultRelInfo *relInfo)
+{
+	List	   *uniqueIndexes = NIL;
+
+	for (int i = 0; i < relInfo->ri_NumIndices; i++)
+	{
+		Relation	indexRelation = relInfo->ri_IndexRelationDescs[i];
+
+		if (indexRelation == NULL)
+			continue;
+
+		/* Detect conflict only for unique indexes */
+		if (!relInfo->ri_IndexRelationInfo[i]->ii_Unique)
+			continue;
+
+		/* Don't support conflict detection for deferrable index */
+		if (!indexRelation->rd_index->indimmediate)
+			continue;
+
+		uniqueIndexes = lappend_oid(uniqueIndexes,
+									RelationGetRelid(indexRelation));
+	}
+
+	relInfo->ri_onConflictArbiterIndexes = uniqueIndexes;
+}
+
+/*
+ * Add SQLSTATE error code to the current conflict report.
+ */
+static int
+errcode_apply_conflict(ConflictType type)
+{
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			return errcode(ERRCODE_UNIQUE_VIOLATION);
+		case CT_UPDATE_DIFFER:
+		case CT_UPDATE_MISSING:
+		case CT_DELETE_DIFFER:
+		case CT_DELETE_MISSING:
+			return errcode(ERRCODE_T_R_SERIALIZATION_FAILURE);
+	}
+
+	Assert(false);
+	return 0;					/* silence compiler warning */
+}
+
+/*
+ * Add an errdetail() line showing conflict detail.
+ *
+ * The DETAIL line comprises of two parts:
+ * 1. Explanation of the conflict type, including the origin and commit
+ *    timestamp of the existing local tuple.
+ * 2. Display of conflicting key, existing local tuple, remote new tuple, and
+ *    replica identity columns, if any. The remote old tuple is excluded as its
+ *    information is covered in the replica identity columns.
+ */
+static int
+errdetail_apply_conflict(EState *estate, ResultRelInfo *relinfo,
+						 ConflictType type, TupleTableSlot *searchslot,
+						 TupleTableSlot *localslot, TupleTableSlot *remoteslot,
+						 Oid indexoid, TransactionId localxmin,
+						 RepOriginId localorigin, TimestampTz localts)
+{
+	StringInfoData err_detail;
+	char	   *val_desc;
+	char	   *origin_name;
+
+	initStringInfo(&err_detail);
+
+	/* First, construct a detailed message describing the type of conflict */
+	switch (type)
+	{
+		case CT_INSERT_EXISTS:
+		case CT_UPDATE_EXISTS:
+			Assert(OidIsValid(indexoid));
+
+			if (localts)
+			{
+				if (localorigin == InvalidRepOriginId)
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified locally in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+				else if (replorigin_by_oid(localorigin, true, &origin_name))
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by origin \"%s\" in transaction %u at %s."),
+									 get_rel_name(indexoid), origin_name,
+									 localxmin, timestamptz_to_str(localts));
+
+				/*
+				 * The origin that modified this row has been removed. This
+				 * can happen if the origin was created by a different apply
+				 * worker and its associated subscription and origin were
+				 * dropped after updating the row, or if the origin was
+				 * manually dropped by the user.
+				 */
+				else
+					appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified by a non-existent origin in transaction %u at %s."),
+									 get_rel_name(indexoid),
+									 localxmin, timestamptz_to_str(localts));
+			}
+			else
+				appendStringInfo(&err_detail, _("Key already exists in unique index \"%s\", modified in transaction %u."),
+								 get_rel_name(indexoid), localxmin);
+
+			break;
+
+		case CT_UPDATE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Updating the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Updating the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_UPDATE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be updated."));
+			break;
+
+		case CT_DELETE_DIFFER:
+			if (localorigin == InvalidRepOriginId)
+				appendStringInfo(&err_detail, _("Deleting the row that was modified locally in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+			else if (replorigin_by_oid(localorigin, true, &origin_name))
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a different origin \"%s\" in transaction %u at %s."),
+								 origin_name, localxmin, timestamptz_to_str(localts));
+
+			/* The origin that modified this row has been removed. */
+			else
+				appendStringInfo(&err_detail, _("Deleting the row that was modified by a non-existent origin in transaction %u at %s."),
+								 localxmin, timestamptz_to_str(localts));
+
+			break;
+
+		case CT_DELETE_MISSING:
+			appendStringInfo(&err_detail, _("Could not find the row to be deleted."));
+			break;
+	}
+
+	Assert(err_detail.len > 0);
+
+	val_desc = build_tuple_value_details(estate, relinfo, type, searchslot,
+										 localslot, remoteslot, indexoid);
+
+	/*
+	 * Next, append the key values, existing local tuple, remote tuple and
+	 * replica identity columns after the message.
+	 */
+	if (val_desc)
+		appendStringInfo(&err_detail, "\n%s", val_desc);
+
+	return errdetail_internal("%s", err_detail.data);
+}
+
+/*
+ * Helper function to build the additional details for conflicting key,
+ * existing local tuple, remote tuple, and replica identity columns.
+ *
+ * If the return value is NULL, it indicates that the current user lacks
+ * permissions to view the columns involved.
+ */
+static char *
+build_tuple_value_details(EState *estate, ResultRelInfo *relinfo,
+						  ConflictType type,
+						  TupleTableSlot *searchslot,
+						  TupleTableSlot *localslot,
+						  TupleTableSlot *remoteslot,
+						  Oid indexoid)
+{
+	Relation	localrel = relinfo->ri_RelationDesc;
+	Oid			relid = RelationGetRelid(localrel);
+	TupleDesc	tupdesc = RelationGetDescr(localrel);
+	StringInfoData tuple_value;
+	char	   *desc = NULL;
+
+	Assert(searchslot || localslot || remoteslot);
+
+	initStringInfo(&tuple_value);
+
+	/*
+	 * Report the conflicting key values in the case of a unique constraint
+	 * violation.
+	 */
+	if (type == CT_INSERT_EXISTS || type == CT_UPDATE_EXISTS)
+	{
+		Assert(OidIsValid(indexoid) && localslot);
+
+		desc = build_index_value_desc(estate, localrel, localslot, indexoid);
+
+		if (desc)
+			appendStringInfo(&tuple_value, _("Key %s"), desc);
+	}
+
+	if (localslot)
+	{
+		/*
+		 * The 'modifiedCols' only applies to the new tuple, hence we pass
+		 * NULL for the existing local tuple.
+		 */
+		desc = ExecBuildSlotValueDescription(relid, localslot, tupdesc,
+											 NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("existing local tuple %s"),
+								 desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Existing local tuple %s"),
+								 desc);
+			}
+		}
+	}
+
+	if (remoteslot)
+	{
+		Bitmapset  *modifiedCols;
+
+		/*
+		 * Although logical replication doesn't maintain the bitmap for the
+		 * columns being inserted, we still use it to create 'modifiedCols'
+		 * for consistency with other calls to ExecBuildSlotValueDescription.
+		 *
+		 * Note that generated columns are formed locally on the subscriber.
+		 */
+		modifiedCols = bms_union(ExecGetInsertedCols(relinfo, estate),
+								 ExecGetUpdatedCols(relinfo, estate));
+		desc = ExecBuildSlotValueDescription(relid, remoteslot, tupdesc,
+											 modifiedCols, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, _("remote tuple %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, _("Remote tuple %s"), desc);
+			}
+		}
+	}
+
+	if (searchslot)
+	{
+		/*
+		 * Note that while index other than replica identity may be used (see
+		 * IsIndexUsableForReplicaIdentityFull for details) to find the tuple
+		 * when applying update or delete, such an index scan may not result in
+		 * a unique tuple and we still compare the complete tuple in such
+		 * cases, thus such indexes are not used here.
+		 */
+		Oid			replica_index = GetRelationIdentityOrPK(localrel);
+
+		Assert(type != CT_INSERT_EXISTS);
+
+		/*
+		 * If the table has a valid replica identity index, build the index
+		 * key value string. Otherwise, construct the full tuple value for
+		 * REPLICA IDENTITY FULL cases.
+		 */
+		if (OidIsValid(replica_index))
+			desc = build_index_value_desc(estate, localrel, searchslot, replica_index);
+		else
+			desc = ExecBuildSlotValueDescription(relid, searchslot, tupdesc, NULL, 64);
+
+		if (desc)
+		{
+			if (tuple_value.len > 0)
+			{
+				appendStringInfoString(&tuple_value, "; ");
+				appendStringInfo(&tuple_value, OidIsValid(replica_index)
+								 ? _("replica identity %s")
+								 : _("replica identity full %s"), desc);
+			}
+			else
+			{
+				appendStringInfo(&tuple_value, OidIsValid(replica_index)
+								 ? _("Replica identity %s")
+								 : _("Replica identity full %s"), desc);
+			}
+		}
+	}
+
+	if (tuple_value.len == 0)
+		return NULL;
+
+	appendStringInfoChar(&tuple_value, '.');
+	return tuple_value.data;
+}
+
+/*
+ * Helper functions to construct a string describing the contents of an index
+ * entry. See BuildIndexValueDescription for details.
+ *
+ * The caller must ensure that the index with the OID 'indexoid' is locked so
+ * that we can fetch and display the conflicting key value.
+ */
+static char *
+build_index_value_desc(EState *estate, Relation localrel, TupleTableSlot *slot,
+					   Oid indexoid)
+{
+	char	   *index_value;
+	Relation	indexDesc;
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	TupleTableSlot *tableslot = slot;
+
+	if (!tableslot)
+		return NULL;
+
+	Assert(CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
+
+	indexDesc = index_open(indexoid, NoLock);
+
+	/*
+	 * If the slot is a virtual slot, copy it into a heap tuple slot as
+	 * FormIndexDatum only works with heap tuple slots.
+	 */
+	if (TTS_IS_VIRTUAL(slot))
+	{
+		tableslot = table_slot_create(localrel, &estate->es_tupleTable);
+		tableslot = ExecCopySlot(tableslot, slot);
+	}
+
+	/*
+	 * Initialize ecxt_scantuple for potential use in FormIndexDatum when
+	 * index expressions are present.
+	 */
+	GetPerTupleExprContext(estate)->ecxt_scantuple = tableslot;
+
+	/*
+	 * The values/nulls arrays passed to BuildIndexValueDescription should be
+	 * the results of FormIndexDatum, which are the "raw" input to the index
+	 * AM.
+	 */
+	FormIndexDatum(BuildIndexInfo(indexDesc), tableslot, estate, values, isnull);
+
+	index_value = BuildIndexValueDescription(indexDesc, values, isnull);
+
+	index_close(indexDesc, NoLock);
+
+	return index_value;
+}
diff --git a/src/backend/replication/logical/meson.build b/src/backend/replication/logical/meson.build
index 3dec36a6de..3d36249d8a 100644
--- a/src/backend/replication/logical/meson.build
+++ b/src/backend/replication/logical/meson.build
@@ -2,6 +2,7 @@
 
 backend_sources += files(
   'applyparallelworker.c',
+  'conflict.c',
   'decode.c',
   'launcher.c',
   'logical.c',
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 245e9be6f2..cdea6295d8 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -167,6 +167,7 @@
 #include "postmaster/bgworker.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/walwriter.h"
+#include "replication/conflict.h"
 #include "replication/logicallauncher.h"
 #include "replication/logicalproto.h"
 #include "replication/logicalrelation.h"
@@ -2481,7 +2482,8 @@ apply_handle_insert_internal(ApplyExecutionData *edata,
 	EState	   *estate = edata->estate;
 
 	/* We must open indexes here. */
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
+	InitConflictIndexes(relinfo);
 
 	/* Do the insert. */
 	TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_INSERT);
@@ -2669,13 +2671,12 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	MemoryContext oldctx;
 
 	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-	ExecOpenIndices(relinfo, false);
+	ExecOpenIndices(relinfo, true);
 
 	found = FindReplTupleInLocalRel(edata, localrel,
 									&relmapentry->remoterel,
 									localindexoid,
 									remoteslot, &localslot);
-	ExecClearTuple(remoteslot);
 
 	/*
 	 * Tuple found.
@@ -2684,6 +2685,28 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	 */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+		{
+			TupleTableSlot *newslot;
+
+			/* Store the new tuple for conflict reporting */
+			newslot = table_slot_create(localrel, &estate->es_tupleTable);
+			slot_store_data(newslot, relmapentry, newtup);
+
+			ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_DIFFER,
+								remoteslot, localslot, newslot,
+								InvalidOid, localxmin, localorigin, localts);
+		}
+
 		/* Process and store remote tuple in the slot */
 		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
@@ -2691,6 +2714,8 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 
 		EvalPlanQualSetSlot(&epqstate, remoteslot);
 
+		InitConflictIndexes(relinfo);
+
 		/* Do the actual update. */
 		TargetPrivilegesCheck(relinfo->ri_RelationDesc, ACL_UPDATE);
 		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
@@ -2698,16 +2723,19 @@ apply_handle_update_internal(ApplyExecutionData *edata,
 	}
 	else
 	{
+		TupleTableSlot *newslot = localslot;
+
+		/* Store the new tuple for conflict reporting */
+		slot_store_data(newslot, relmapentry, newtup);
+
 		/*
 		 * The tuple to be updated could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be updated "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_UPDATE_MISSING,
+							remoteslot, NULL, newslot,
+							InvalidOid, InvalidTransactionId,
+							InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -2830,6 +2858,20 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 	/* If found delete it. */
 	if (found)
 	{
+		RepOriginId localorigin;
+		TransactionId localxmin;
+		TimestampTz localts;
+
+		/*
+		 * Report the conflict if the tuple was modified by a different
+		 * origin.
+		 */
+		if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+			localorigin != replorigin_session_origin)
+			ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_DIFFER,
+								remoteslot, localslot, NULL,
+								InvalidOid, localxmin, localorigin, localts);
+
 		EvalPlanQualSetSlot(&epqstate, localslot);
 
 		/* Do the actual delete. */
@@ -2841,13 +2883,11 @@ apply_handle_delete_internal(ApplyExecutionData *edata,
 		/*
 		 * The tuple to be deleted could not be found.  Do nothing except for
 		 * emitting a log message.
-		 *
-		 * XXX should this be promoted to ereport(LOG) perhaps?
 		 */
-		elog(DEBUG1,
-			 "logical replication did not find row to be deleted "
-			 "in replication target relation \"%s\"",
-			 RelationGetRelationName(localrel));
+		ReportApplyConflict(estate, relinfo, LOG, CT_DELETE_MISSING,
+							remoteslot, NULL, NULL,
+							InvalidOid, InvalidTransactionId,
+							InvalidRepOriginId, 0);
 	}
 
 	/* Cleanup. */
@@ -3015,6 +3055,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				Relation	partrel_new;
 				bool		found;
 				EPQState	epqstate;
+				RepOriginId localorigin;
+				TransactionId localxmin;
+				TimestampTz localts;
 
 				/* Get the matching local tuple from the partition. */
 				found = FindReplTupleInLocalRel(edata, partrel,
@@ -3023,19 +3066,43 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 												remoteslot_part, &localslot);
 				if (!found)
 				{
+					TupleTableSlot *newslot = localslot;
+
+					/* Store the new tuple for conflict reporting */
+					slot_store_data(newslot, part_entry, newtup);
+
 					/*
 					 * The tuple to be updated could not be found.  Do nothing
 					 * except for emitting a log message.
-					 *
-					 * XXX should this be promoted to ereport(LOG) perhaps?
 					 */
-					elog(DEBUG1,
-						 "logical replication did not find row to be updated "
-						 "in replication target relation's partition \"%s\"",
-						 RelationGetRelationName(partrel));
+					ReportApplyConflict(estate, partrelinfo,
+										LOG, CT_UPDATE_MISSING,
+										remoteslot_part, NULL, newslot,
+										InvalidOid, InvalidTransactionId,
+										InvalidRepOriginId, 0);
+
 					return;
 				}
 
+				/*
+				 * Report the conflict if the tuple was modified by a
+				 * different origin.
+				 */
+				if (GetTupleTransactionInfo(localslot, &localxmin, &localorigin, &localts) &&
+					localorigin != replorigin_session_origin)
+				{
+					TupleTableSlot *newslot;
+
+					/* Store the new tuple for conflict reporting */
+					newslot = table_slot_create(partrel, &estate->es_tupleTable);
+					slot_store_data(newslot, part_entry, newtup);
+
+					ReportApplyConflict(estate, partrelinfo, LOG, CT_UPDATE_DIFFER,
+										remoteslot_part, localslot, newslot,
+										InvalidOid, localxmin, localorigin,
+										localts);
+				}
+
 				/*
 				 * Apply the update to the local tuple, putting the result in
 				 * remoteslot_part.
@@ -3046,7 +3113,6 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 				MemoryContextSwitchTo(oldctx);
 
 				EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1, NIL);
-				ExecOpenIndices(partrelinfo, false);
 
 				/*
 				 * Does the updated tuple still satisfy the current
@@ -3063,6 +3129,9 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 					 * work already done above to find the local tuple in the
 					 * partition.
 					 */
+					ExecOpenIndices(partrelinfo, true);
+					InitConflictIndexes(partrelinfo);
+
 					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc,
 										  ACL_UPDATE);
@@ -3110,6 +3179,8 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 											 get_namespace_name(RelationGetNamespace(partrel_new)),
 											 RelationGetRelationName(partrel_new));
 
+					ExecOpenIndices(partrelinfo, false);
+
 					/* DELETE old tuple found in the old partition. */
 					EvalPlanQualSetSlot(&epqstate, localslot);
 					TargetPrivilegesCheck(partrelinfo->ri_RelationDesc, ACL_DELETE);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 9770752ea3..f1905f697e 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -228,6 +228,10 @@ extern void ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
 										TupleTableSlot *slot, EState *estate);
 extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 								 TupleTableSlot *slot, EState *estate);
+extern char *ExecBuildSlotValueDescription(Oid reloid, TupleTableSlot *slot,
+										   TupleDesc tupdesc,
+										   Bitmapset *modifiedCols,
+										   int maxfieldlen);
 extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
 extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
 extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
@@ -636,6 +640,7 @@ extern List *ExecInsertIndexTuples(ResultRelInfo *resultRelInfo,
 extern bool ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo,
 									  TupleTableSlot *slot,
 									  EState *estate, ItemPointer conflictTid,
+									  ItemPointer tupleid,
 									  List *arbiterIndexes);
 extern void check_exclusion_constraint(Relation heap, Relation index,
 									   IndexInfo *indexInfo,
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
new file mode 100644
index 0000000000..02cb84da7e
--- /dev/null
+++ b/src/include/replication/conflict.h
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ * conflict.h
+ *	   Exports for conflicts logging.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONFLICT_H
+#define CONFLICT_H
+
+#include "nodes/execnodes.h"
+#include "utils/timestamp.h"
+
+/*
+ * Conflict types that could occur while applying remote changes.
+ */
+typedef enum
+{
+	/* The row to be inserted violates unique constraint */
+	CT_INSERT_EXISTS,
+
+	/* The row to be updated was modified by a different origin */
+	CT_UPDATE_DIFFER,
+
+	/* The updated row value violates unique constraint */
+	CT_UPDATE_EXISTS,
+
+	/* The row to be updated is missing */
+	CT_UPDATE_MISSING,
+
+	/* The row to be deleted was modified by a different origin */
+	CT_DELETE_DIFFER,
+
+	/* The row to be deleted is missing */
+	CT_DELETE_MISSING,
+
+	/*
+	 * Other conflicts, such as exclusion constraint violations, involve more
+	 * complex rules than simple equality checks. These conflicts are left for
+	 * future improvements.
+	 */
+} ConflictType;
+
+extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
+									TransactionId *xmin,
+									RepOriginId *localorigin,
+									TimestampTz *localts);
+extern void ReportApplyConflict(EState *estate, ResultRelInfo *relinfo,
+								int elevel, ConflictType type,
+								TupleTableSlot *searchslot,
+								TupleTableSlot *localslot,
+								TupleTableSlot *remoteslot,
+								Oid indexoid, TransactionId localxmin,
+								RepOriginId localorigin, TimestampTz localts);
+extern void InitConflictIndexes(ResultRelInfo *relInfo);
+
+#endif
diff --git a/src/test/subscription/t/001_rep_changes.pl b/src/test/subscription/t/001_rep_changes.pl
index 471e981962..d377e7ae2b 100644
--- a/src/test/subscription/t/001_rep_changes.pl
+++ b/src/test/subscription/t/001_rep_changes.pl
@@ -331,13 +331,8 @@ is( $result, qq(1|bar
 2|baz),
 	'update works with REPLICA IDENTITY FULL and a primary key');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber->append_conf('postgresql.conf', "log_min_messages = debug1");
-$node_subscriber->reload;
-
 $node_subscriber->safe_psql('postgres', "DELETE FROM tab_full_pk");
+$node_subscriber->safe_psql('postgres', "DELETE FROM tab_full WHERE a = 25");
 
 # Note that the current location of the log file is not grabbed immediately
 # after reloading the configuration, but after sending one SQL command to
@@ -346,16 +341,21 @@ my $log_location = -s $node_subscriber->logfile;
 
 $node_publisher->safe_psql('postgres',
 	"UPDATE tab_full_pk SET b = 'quux' WHERE a = 1");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab_full SET a = a + 1 WHERE a = 25");
 $node_publisher->safe_psql('postgres', "DELETE FROM tab_full_pk WHERE a = 2");
 
 $node_publisher->wait_for_catchup('tap_sub');
 
 my $logfile = slurp_file($node_subscriber->logfile, $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(1, quux\); replica identity \(a\)=\(1\)/m,
+	'update target row is missing');
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab_full": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(26\); replica identity full \(25\)/m,
 	'update target row is missing');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab_full_pk"/,
+	  qr/conflict detected on relation "public.tab_full_pk": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(2\)/m,
 	'delete target row is missing');
 
 $node_subscriber->append_conf('postgresql.conf',
@@ -517,7 +517,7 @@ is($result, qq(1052|1|1002),
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(a), max(a) FROM tab_full");
-is($result, qq(21|0|100), 'check replicated insert after alter publication');
+is($result, qq(19|0|100), 'check replicated insert after alter publication');
 
 # check restart on rename
 $oldpid = $node_publisher->safe_psql('postgres',
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
index 29580525a9..cf91542ed0 100644
--- a/src/test/subscription/t/013_partition.pl
+++ b/src/test/subscription/t/013_partition.pl
@@ -343,13 +343,6 @@ $result =
   $node_subscriber2->safe_psql('postgres', "SELECT a FROM tab1 ORDER BY 1");
 is($result, qq(), 'truncate of tab1 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab1 VALUES (1, 'foo'), (4, 'bar'), (10, 'baz')");
 
@@ -372,22 +365,18 @@ $node_publisher->wait_for_catchup('sub2');
 
 my $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(null, 4, quux\); replica identity \(a\)=\(4\)/,
 	'update target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_1"/,
+	  qr/conflict detected on relation "public.tab1_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab1_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_2_2"/,
+	  qr/conflict detected on relation "public.tab1_2_2": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(4\)/,
 	'delete target row is missing in tab1_2_2');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab1_def"/,
+	  qr/conflict detected on relation "public.tab1_def": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(10\)/,
 	'delete target row is missing in tab1_def');
 
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
-
 # Tests for replication using root table identity and schema
 
 # publisher
@@ -773,13 +762,6 @@ pub_tab2|3|yyy
 pub_tab2|5|zzz
 xxx_c|6|aaa), 'inserts into tab2 replicated');
 
-# Check that subscriber handles cases where update/delete target tuple
-# is missing.  We have to look for the DEBUG1 log messages about that,
-# so temporarily bump up the log verbosity.
-$node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = debug1");
-$node_subscriber1->reload;
-
 $node_subscriber1->safe_psql('postgres', "DELETE FROM tab2");
 
 # Note that the current location of the log file is not grabbed immediately
@@ -796,15 +778,34 @@ $node_publisher->wait_for_catchup('sub2');
 
 $logfile = slurp_file($node_subscriber1->logfile(), $log_location);
 ok( $logfile =~
-	  qr/logical replication did not find row to be updated in replication target relation's partition "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_missing.*\n.*DETAIL:.* Could not find the row to be updated.*\n.*Remote tuple \(pub_tab2, quux, 5\); replica identity \(a\)=\(5\)/,
 	'update target row is missing in tab2_1');
 ok( $logfile =~
-	  qr/logical replication did not find row to be deleted in replication target relation "tab2_1"/,
+	  qr/conflict detected on relation "public.tab2_1": conflict=delete_missing.*\n.*DETAIL:.* Could not find the row to be deleted.*\n.*Replica identity \(a\)=\(1\)/,
 	'delete target row is missing in tab2_1');
 
+# Enable the track_commit_timestamp to detect the conflict when attempting
+# to update a row that was previously modified by a different origin.
+$node_subscriber1->append_conf('postgresql.conf',
+	'track_commit_timestamp = on');
+$node_subscriber1->restart;
+
+$node_subscriber1->safe_psql('postgres',
+	"INSERT INTO tab2 VALUES (3, 'yyy')");
+$node_publisher->safe_psql('postgres',
+	"UPDATE tab2 SET b = 'quux' WHERE a = 3");
+
+$node_publisher->wait_for_catchup('sub_viaroot');
+
+$logfile = slurp_file($node_subscriber1->logfile(), $log_location);
+ok( $logfile =~
+	  qr/conflict detected on relation "public.tab2_1": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified locally in transaction [0-9]+ at .*\n.*Existing local tuple \(yyy, null, 3\); remote tuple \(pub_tab2, quux, 3\); replica identity \(a\)=\(3\)/,
+	'updating a tuple that was modified by a different origin');
+
+# The remaining tests no longer test conflict detection.
 $node_subscriber1->append_conf('postgresql.conf',
-	"log_min_messages = warning");
-$node_subscriber1->reload;
+	'track_commit_timestamp = off');
+$node_subscriber1->restart;
 
 # Test that replication continues to work correctly after altering the
 # partition of a partitioned target table.
diff --git a/src/test/subscription/t/029_on_error.pl b/src/test/subscription/t/029_on_error.pl
index 0ab57a4b5b..2f099a74f3 100644
--- a/src/test/subscription/t/029_on_error.pl
+++ b/src/test/subscription/t/029_on_error.pl
@@ -30,7 +30,7 @@ sub test_skip_lsn
 	# ERROR with its CONTEXT when retrieving this information.
 	my $contents = slurp_file($node_subscriber->logfile, $offset);
 	$contents =~
-	  qr/duplicate key value violates unique constraint "tbl_pkey".*\n.*DETAIL:.*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
+	  qr/conflict detected on relation "public.tbl".*\n.*DETAIL:.* Key already exists in unique index "tbl_pkey", modified by .*origin.* transaction \d+ at .*\n.*Key \(i\)=\(\d+\); existing local tuple .*; remote tuple .*\n.*CONTEXT:.* for replication target relation "public.tbl" in transaction \d+, finished at ([[:xdigit:]]+\/[[:xdigit:]]+)/m
 	  or die "could not get error-LSN";
 	my $lsn = $1;
 
@@ -83,6 +83,7 @@ $node_subscriber->append_conf(
 	'postgresql.conf',
 	qq[
 max_prepared_transactions = 10
+track_commit_timestamp = on
 ]);
 $node_subscriber->start;
 
@@ -93,6 +94,7 @@ $node_publisher->safe_psql(
 	'postgres',
 	qq[
 CREATE TABLE tbl (i INT, t BYTEA);
+ALTER TABLE tbl REPLICA IDENTITY FULL;
 INSERT INTO tbl VALUES (1, NULL);
 ]);
 $node_subscriber->safe_psql(
@@ -144,13 +146,14 @@ COMMIT;
 test_skip_lsn($node_publisher, $node_subscriber,
 	"(2, NULL)", "2", "test skipping transaction");
 
-# Test for PREPARE and COMMIT PREPARED. Insert the same data to tbl and
-# PREPARE the transaction, raising an error. Then skip the transaction.
+# Test for PREPARE and COMMIT PREPARED. Update the data and PREPARE the
+# transaction, raising an error on the subscriber due to violation of the
+# unique constraint on tbl. Then skip the transaction.
 $node_publisher->safe_psql(
 	'postgres',
 	qq[
 BEGIN;
-INSERT INTO tbl VALUES (1, NULL);
+UPDATE tbl SET i = 2;
 PREPARE TRANSACTION 'gtx';
 COMMIT PREPARED 'gtx';
 ]);
diff --git a/src/test/subscription/t/030_origin.pl b/src/test/subscription/t/030_origin.pl
index 056561f008..01536a13e7 100644
--- a/src/test/subscription/t/030_origin.pl
+++ b/src/test/subscription/t/030_origin.pl
@@ -27,9 +27,14 @@ my $stderr;
 my $node_A = PostgreSQL::Test::Cluster->new('node_A');
 $node_A->init(allows_streaming => 'logical');
 $node_A->start;
+
 # node_B
 my $node_B = PostgreSQL::Test::Cluster->new('node_B');
 $node_B->init(allows_streaming => 'logical');
+
+# Enable the track_commit_timestamp to detect the conflict when attempting to
+# update a row that was previously modified by a different origin.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $node_B->start;
 
 # Create table on node_A
@@ -139,6 +144,48 @@ is($result, qq(),
 	'Remote data originating from another node (not the publisher) is not replicated when origin parameter is none'
 );
 
+###############################################################################
+# Check that the conflict can be detected when attempting to update or
+# delete a row that was previously modified by a different source.
+###############################################################################
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (32);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(32), 'The node_A data replicated to node_B');
+
+# The update should update the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "UPDATE tab SET a = 33 WHERE a = 32;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=update_differ.*\n.*DETAIL:.* Updating the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(32\); remote tuple \(33\); replica identity \(a\)=\(32\)/
+);
+
+$node_B->safe_psql('postgres', "DELETE FROM tab;");
+$node_A->safe_psql('postgres', "INSERT INTO tab VALUES (33);");
+
+$node_A->wait_for_catchup($subname_BA);
+$node_B->wait_for_catchup($subname_AB);
+
+$result = $node_B->safe_psql('postgres', "SELECT * FROM tab ORDER BY 1;");
+is($result, qq(33), 'The node_A data replicated to node_B');
+
+# The delete should remove the row on node B that was inserted by node A.
+$node_C->safe_psql('postgres', "DELETE FROM tab WHERE a = 33;");
+
+$node_B->wait_for_log(
+	qr/conflict detected on relation "public.tab": conflict=delete_differ.*\n.*DETAIL:.* Deleting the row that was modified by a different origin ".*" in transaction [0-9]+ at .*\n.*Existing local tuple \(33\); replica identity \(a\)=\(33\)/
+);
+
+# The remaining tests no longer test conflict detection.
+$node_B->append_conf('postgresql.conf', 'track_commit_timestamp = off');
+$node_B->restart;
+
 ###############################################################################
 # Specifying origin = NONE indicates that the publisher should only replicate the
 # changes that are generated locally from node_B, but in this case since the
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 547d14b3e7..6d424c8918 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -467,6 +467,7 @@ ConditionVariableMinimallyPadded
 ConditionalStack
 ConfigData
 ConfigVariable
+ConflictType
 ConnCacheEntry
 ConnCacheKey
 ConnParams
-- 
2.28.0.windows.1

From a453371d0c706f8cbc8e177629309fc9922612f7 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Tue, 20 Aug 2024 15:02:17 +0800
Subject: [PATCH v19 2/2] Collect statistics about conflicts in logical
 replication

This commit adds columns in view pg_stat_subscription_stats to show
information about the conflict which occur during the application of
logical replication changes. Currently, the following columns are added.

insert_exists_count:
	Number of times a row insertion violated a NOT DEFERRABLE unique constraint.
update_differ_count:
	Number of times an update was performed on a row that was previously modified by another origin.
update_exists_count:
	Number of times that the updated value of a row violates a NOT DEFERRABLE unique constraint.
update_missing_count:
	Number of times that the tuple to be updated is missing.
delete_differ_count:
	Number of times a delete was performed on a row that was previously modified by another origin.
delete_missing_count:
	Number of times that the tuple to be deleted is missing.

The update_differ and delete_differ conflicts can be detected only when
track_commit_timestamp is enabled.
---
 doc/src/sgml/logical-replication.sgml         |   5 +-
 doc/src/sgml/monitoring.sgml                  |  70 ++++++++-
 src/backend/catalog/system_views.sql          |   6 +
 src/backend/replication/logical/conflict.c    |   5 +-
 .../utils/activity/pgstat_subscription.c      |  17 ++
 src/backend/utils/adt/pgstatfuncs.c           |  33 +++-
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/pgstat.h                          |   4 +
 src/include/replication/conflict.h            |   7 +
 src/test/regress/expected/rules.out           |   8 +-
 src/test/subscription/t/026_stats.pl          | 145 ++++++++++++++++--
 11 files changed, 280 insertions(+), 26 deletions(-)

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 8cbd8624a5..2ede190ac8 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1585,8 +1585,9 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
   </para>
 
   <para>
-   Additional logging is triggered in the following <firstterm>conflict</firstterm>
-   cases:
+   Additional logging is triggered and the conflict statistics are collected (displayed in the
+   <link linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link> view)
+   in the following <firstterm>conflict</firstterm> cases:
    <variablelist>
     <varlistentry>
      <term><literal>insert_exists</literal></term>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 55417a6fa9..c787591d33 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -507,7 +507,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
      <row>
       <entry><structname>pg_stat_subscription_stats</structname><indexterm><primary>pg_stat_subscription_stats</primary></indexterm></entry>
-      <entry>One row per subscription, showing statistics about errors.
+      <entry>One row per subscription, showing statistics about errors and conflicts.
       See <link linkend="monitoring-pg-stat-subscription-stats">
       <structname>pg_stat_subscription_stats</structname></link> for details.
       </entry>
@@ -2171,6 +2171,74 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>insert_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a row insertion violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times an update was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       option is enabled on the subscriber
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_exists_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the updated value of a row violated a
+       <literal>NOT DEFERRABLE</literal> unique constraint while applying
+       changes
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>update_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be updated was not found while applying
+       changes
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_differ_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a delete was performed on a row that was previously
+       modified by another source while applying changes. This conflict is
+       counted only when the
+       <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+       option is enabled on the subscriber
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>delete_missing_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times that the tuple to be deleted was not found while applying
+       changes
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 19cabc9a47..fcdd199117 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1365,6 +1365,12 @@ CREATE VIEW pg_stat_subscription_stats AS
         s.subname,
         ss.apply_error_count,
         ss.sync_error_count,
+        ss.insert_exists_count,
+        ss.update_differ_count,
+        ss.update_exists_count,
+        ss.update_missing_count,
+        ss.delete_differ_count,
+        ss.delete_missing_count,
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index 0bc7959980..02f7892cb2 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -17,8 +17,9 @@
 #include "access/commit_ts.h"
 #include "access/tableam.h"
 #include "executor/executor.h"
+#include "pgstat.h"
 #include "replication/conflict.h"
-#include "replication/logicalrelation.h"
+#include "replication/worker_internal.h"
 #include "storage/lmgr.h"
 #include "utils/lsyscache.h"
 
@@ -114,6 +115,8 @@ ReportApplyConflict(EState *estate, ResultRelInfo *relinfo, int elevel,
 	Assert(!OidIsValid(indexoid) ||
 		   CheckRelationOidLockedByMe(indexoid, RowExclusiveLock, true));
 
+	pgstat_report_subscription_conflict(MySubscription->oid, type);
+
 	ereport(elevel,
 			errcode_apply_conflict(type),
 			errmsg("conflict detected on relation \"%s.%s\": conflict=%s",
diff --git a/src/backend/utils/activity/pgstat_subscription.c b/src/backend/utils/activity/pgstat_subscription.c
index d9af8de658..e06c92727e 100644
--- a/src/backend/utils/activity/pgstat_subscription.c
+++ b/src/backend/utils/activity/pgstat_subscription.c
@@ -39,6 +39,21 @@ pgstat_report_subscription_error(Oid subid, bool is_apply_error)
 		pending->sync_error_count++;
 }
 
+/*
+ * Report a subscription conflict.
+ */
+void
+pgstat_report_subscription_conflict(Oid subid, ConflictType type)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStat_BackendSubEntry *pending;
+
+	entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_SUBSCRIPTION,
+										  InvalidOid, subid, NULL);
+	pending = entry_ref->pending;
+	pending->conflict_count[type]++;
+}
+
 /*
  * Report creating the subscription.
  */
@@ -101,6 +116,8 @@ pgstat_subscription_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 #define SUB_ACC(fld) shsubent->stats.fld += localent->fld
 	SUB_ACC(apply_error_count);
 	SUB_ACC(sync_error_count);
+	for (int i = 0; i < CONFLICT_NUM_TYPES; i++)
+		SUB_ACC(conflict_count[i]);
 #undef SUB_ACC
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3221137123..870aee8e7b 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1966,13 +1966,14 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	4
+#define PG_STAT_GET_SUBSCRIPTION_STATS_COLS	10
 	Oid			subid = PG_GETARG_OID(0);
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBSCRIPTION_STATS_COLS] = {0};
 	PgStat_StatSubEntry *subentry;
 	PgStat_StatSubEntry allzero;
+	int			i = 0;
 
 	/* Get subscription stats */
 	subentry = pgstat_fetch_stat_subscription(subid);
@@ -1985,7 +1986,19 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "sync_error_count",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "insert_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "update_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "update_exists_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "update_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "delete_differ_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "delete_missing_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -1997,19 +2010,25 @@ pg_stat_get_subscription_stats(PG_FUNCTION_ARGS)
 	}
 
 	/* subid */
-	values[0] = ObjectIdGetDatum(subid);
+	values[i++] = ObjectIdGetDatum(subid);
 
 	/* apply_error_count */
-	values[1] = Int64GetDatum(subentry->apply_error_count);
+	values[i++] = Int64GetDatum(subentry->apply_error_count);
 
 	/* sync_error_count */
-	values[2] = Int64GetDatum(subentry->sync_error_count);
+	values[i++] = Int64GetDatum(subentry->sync_error_count);
+
+	/* conflict count */
+	for (int nconflict = 0; nconflict < CONFLICT_NUM_TYPES; nconflict++)
+		values[i++] = Int64GetDatum(subentry->conflict_count[nconflict]);
 
 	/* stats_reset */
 	if (subentry->stat_reset_timestamp == 0)
-		nulls[3] = true;
+		nulls[i] = true;
 	else
-		values[3] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+		values[i] = TimestampTzGetDatum(subentry->stat_reset_timestamp);
+
+	Assert(i + 1 == PG_STAT_GET_SUBSCRIPTION_STATS_COLS);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 4abc6d9526..3d5c2957c9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5538,9 +5538,9 @@
 { oid => '6231', descr => 'statistics: information about subscription stats',
   proname => 'pg_stat_get_subscription_stats', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,int8,int8,timestamptz}',
-  proargmodes => '{i,o,o,o,o}',
-  proargnames => '{subid,subid,apply_error_count,sync_error_count,stats_reset}',
+  proallargtypes => '{oid,oid,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,apply_error_count,sync_error_count,insert_exists_count,update_differ_count,update_exists_count,update_missing_count,delete_differ_count,delete_missing_count,stats_reset}',
   prosrc => 'pg_stat_get_subscription_stats' },
 { oid => '6118', descr => 'statistics: information about subscription',
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index f63159c55c..adb91f5ab2 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -15,6 +15,7 @@
 #include "datatype/timestamp.h"
 #include "portability/instr_time.h"
 #include "postmaster/pgarch.h"	/* for MAX_XFN_CHARS */
+#include "replication/conflict.h"
 #include "utils/backend_progress.h" /* for backward compatibility */
 #include "utils/backend_status.h"	/* for backward compatibility */
 #include "utils/relcache.h"
@@ -165,6 +166,7 @@ typedef struct PgStat_BackendSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 } PgStat_BackendSubEntry;
 
 /* ----------
@@ -423,6 +425,7 @@ typedef struct PgStat_StatSubEntry
 {
 	PgStat_Counter apply_error_count;
 	PgStat_Counter sync_error_count;
+	PgStat_Counter conflict_count[CONFLICT_NUM_TYPES];
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatSubEntry;
 
@@ -725,6 +728,7 @@ extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  */
 
 extern void pgstat_report_subscription_error(Oid subid, bool is_apply_error);
+extern void pgstat_report_subscription_conflict(Oid subid, ConflictType conflict);
 extern void pgstat_create_subscription(Oid subid);
 extern void pgstat_drop_subscription(Oid subid);
 extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid);
diff --git a/src/include/replication/conflict.h b/src/include/replication/conflict.h
index 02cb84da7e..7232c8889b 100644
--- a/src/include/replication/conflict.h
+++ b/src/include/replication/conflict.h
@@ -14,6 +14,11 @@
 
 /*
  * Conflict types that could occur while applying remote changes.
+ *
+ * This enum is used in statistics collection (see
+ * PgStat_StatSubEntry::conflict_count) as well, therefore, when adding new
+ * values or reordering existing ones, ensure to review and potentially adjust
+ * the corresponding statistics collection codes.
  */
 typedef enum
 {
@@ -42,6 +47,8 @@ typedef enum
 	 */
 } ConflictType;
 
+#define CONFLICT_NUM_TYPES (CT_DELETE_MISSING + 1)
+
 extern bool GetTupleTransactionInfo(TupleTableSlot *localslot,
 									TransactionId *xmin,
 									RepOriginId *localorigin,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 862433ee52..1985d2ffad 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2139,9 +2139,15 @@ pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
     ss.sync_error_count,
+    ss.insert_exists_count,
+    ss.update_differ_count,
+    ss.update_exists_count,
+    ss.update_missing_count,
+    ss.delete_differ_count,
+    ss.delete_missing_count,
     ss.stats_reset
    FROM pg_subscription s,
-    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, stats_reset);
+    LATERAL pg_stat_get_subscription_stats(s.oid) ss(subid, apply_error_count, sync_error_count, insert_exists_count, update_differ_count, update_exists_count, update_missing_count, delete_differ_count, delete_missing_count, stats_reset);
 pg_stat_sys_indexes| SELECT relid,
     indexrelid,
     schemaname,
diff --git a/src/test/subscription/t/026_stats.pl b/src/test/subscription/t/026_stats.pl
index fb3e5629b3..47735282a9 100644
--- a/src/test/subscription/t/026_stats.pl
+++ b/src/test/subscription/t/026_stats.pl
@@ -16,6 +16,15 @@ $node_publisher->start;
 # Create subscriber node.
 my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
 $node_subscriber->init;
+
+# Enable track_commit_timestamp to detect origin-differ conflicts in logical
+# replication. Reduce wal_retrieve_retry_interval to 1ms to accelerate the
+# restart of the logical replication worker after encountering a conflict.
+$node_subscriber->append_conf(
+	'postgresql.conf', q{
+track_commit_timestamp = on
+wal_retrieve_retry_interval = 1ms
+});
 $node_subscriber->start;
 
 
@@ -30,6 +39,7 @@ sub create_sub_pub_w_errors
 		qq[
 	BEGIN;
 	CREATE TABLE $table_name(a int);
+	ALTER TABLE $table_name REPLICA IDENTITY FULL;
 	INSERT INTO $table_name VALUES (1);
 	COMMIT;
 	]);
@@ -95,7 +105,7 @@ sub create_sub_pub_w_errors
 	$node_subscriber->poll_query_until(
 		$db,
 		qq[
-	SELECT apply_error_count > 0
+	SELECT apply_error_count > 0 AND insert_exists_count > 0
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub_name'
 	])
@@ -105,6 +115,89 @@ sub create_sub_pub_w_errors
 	# Truncate test table so that apply worker can continue.
 	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
 
+	# Insert a row on the subscriber.
+	$node_subscriber->safe_psql($db, qq(INSERT INTO $table_name VALUES (2)));
+
+   # Update the test table on the publisher. This operation will raise an
+   # error on the subscriber due to a violation of the unique constraint on
+   # the test table.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the subscriber to report an update_exists conflict.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_exists_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_exists conflict for subscription '$sub_name');
+
+	# Truncate test table to ensure the upcoming update operation is skipped
+	# and the test can continue.
+	$node_subscriber->safe_psql($db, qq(TRUNCATE $table_name));
+
+	# Delete data from the test table on the publisher. This delete operation
+	# should be skipped on the subscriber since the table is already empty.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	# Wait for the subscriber to report tuple missing conflict.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_missing_count > 0 AND delete_missing_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for tuple missing conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_publisher->safe_psql($db, qq(INSERT INTO $table_name VALUES (1)));
+	$node_publisher->wait_for_catchup($sub_name);
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (1);
+	));
+
+	# Update the data in the test table on the publisher. This should generate
+	# a conflict because it attempts to update a row on the subscriber that has
+	# been modified by a different origin.
+	$node_publisher->safe_psql($db, qq(UPDATE $table_name SET a = 2;));
+
+	# Wait for the subscriber to report an update_differ conflict.
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT update_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for update_differ conflict for subscription '$sub_name');
+
+	# Prepare data for further tests.
+	$node_subscriber->safe_psql($db, qq(
+		TRUNCATE $table_name;
+		INSERT INTO $table_name VALUES (2);
+	));
+
+	# Delete data from the test table on the publisher. This should generate a
+	# conflict because it attempts to delete a row on the subscriber that has
+	# been modified by a different origin.
+	$node_publisher->safe_psql($db, qq(DELETE FROM $table_name;));
+
+	$node_subscriber->poll_query_until(
+		$db,
+		qq[
+	SELECT delete_differ_count > 0
+	FROM pg_stat_subscription_stats
+	WHERE subname = '$sub_name'
+	])
+	  or die
+	  qq(Timed out while waiting for delete_differ conflict for subscription '$sub_name');
+
 	return ($pub_name, $sub_name);
 }
 
@@ -128,12 +221,18 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_exists_count > 0,
+	update_missing_count > 0,
+	delete_differ_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
-	qq(Check that apply errors and sync errors are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
+	qq(t|t|t|t|t|t|t|t|t),
+	qq(Check that apply errors, sync errors, and conflicts are both > 0 and stats_reset is NULL for subscription '$sub1_name'.)
 );
 
 # Reset a single subscription
@@ -146,12 +245,18 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_exists_count = 0,
+	update_missing_count = 0,
+	delete_differ_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
-	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
+	qq(t|t|t|t|t|t|t|t|t),
+	qq(Confirm that apply errors, sync errors, and conflicts are both 0 and stats_reset is not NULL after reset for subscription '$sub1_name'.)
 );
 
 # Get reset timestamp
@@ -186,12 +291,18 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count > 0,
 	sync_error_count > 0,
+	insert_exists_count > 0,
+	update_differ_count > 0,
+	update_exists_count > 0,
+	update_missing_count > 0,
+	delete_differ_count > 0,
+	delete_missing_count > 0,
 	stats_reset IS NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
-	qq(Confirm that apply errors and sync errors are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
+	qq(t|t|t|t|t|t|t|t|t),
+	qq(Confirm that apply errors, sync errors, and conflicts are both > 0 and stats_reset is NULL for sub '$sub2_name'.)
 );
 
 # Reset all subscriptions
@@ -203,24 +314,36 @@ is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_exists_count = 0,
+	update_missing_count = 0,
+	delete_differ_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub1_name')
 	),
-	qq(t|t|t),
-	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
+	qq(t|t|t|t|t|t|t|t|t),
+	qq(Confirm that apply errors, sync errors, and conflicts are both 0 and stats_reset is not NULL for sub '$sub1_name' after reset.)
 );
 
 is( $node_subscriber->safe_psql(
 		$db,
 		qq(SELECT apply_error_count = 0,
 	sync_error_count = 0,
+	insert_exists_count = 0,
+	update_differ_count = 0,
+	update_exists_count = 0,
+	update_missing_count = 0,
+	delete_differ_count = 0,
+	delete_missing_count = 0,
 	stats_reset IS NOT NULL
 	FROM pg_stat_subscription_stats
 	WHERE subname = '$sub2_name')
 	),
-	qq(t|t|t),
-	qq(Confirm that apply errors and sync errors are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
+	qq(t|t|t|t|t|t|t|t|t),
+	qq(Confirm that apply errors, sync errors, and conflicts are both 0 and stats_reset is not NULL for sub '$sub2_name' after reset.)
 );
 
 $reset_time1 = $node_subscriber->safe_psql($db,
-- 
2.30.0.windows.2

From c327b27e01bb2f5ab290d4b70fa990d328d84f13 Mon Sep 17 00:00:00 2001
From: Hou Zhijie <houzj.fnst@cn.fujitsu.com>
Date: Tue, 13 Aug 2024 16:08:36 +0800
Subject: [PATCH v19 1/2] Doc: explain the log format of logical replication
 conflict

This commit adds a detailed explanation of the log format for logical
replication conflicts to the documentation. It aims to help users better
understand conflict logs.
---
 doc/src/sgml/logical-replication.sgml | 69 +++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 885a2d70ae..8cbd8624a5 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1666,6 +1666,75 @@ test_sub=# SELECT * FROM t1 ORDER BY id;
     log.
   </para>
 
+  <para>
+   The log format for logical replication conflicts is as follows:
+<screen>
+LOG:  conflict detected on relation "schemaname.tablename": conflict=<literal>conflict_type</literal>
+DETAIL:  <literal>detailed explaination</literal>.
+<literal>Key</literal> (column_name, ...)=(column_name, ...); <literal>existing local tuple</literal> (column_name, ...)=(column_name, ...); <literal>remote tuple</literal> (column_name, ...)=(column_name, ...); <literal>replica identity</literal> (column_name, ...)=(column_name, ...).
+</screen>
+   The log provides the following information:
+   <itemizedlist>
+    <listitem>
+     <para>
+      The <literal>LOG</literal> line includes the name of the local relation
+      involved in the conflict and the <literal>conflict_type</literal> (e.g.,
+      <literal>insert_exists</literal>, <literal>update_exists</literal>).
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      The origin, transaction ID, and commit timestamp of the transaction that
+      modified the existing local tuple, if available, are included in the
+      <literal>detailed explanation</literal> section of the first sentence in
+      the <literal>DETAIL</literal> line.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      The <literal>key</literal> section in the second sentence of the
+      <literal>DETAIL</literal> line includes the key values of the tuple that
+      already exists in the local relation for <literal>insert_exists</literal>
+      or <literal>update_exists</literal> conflicts.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      The <literal>existing local tuple</literal> section in the second
+      sentence of the <literal>DETAIL</literal> line includes the local tuple
+      if its origin differs from the remote tuple in cases of
+      <literal>update_differ</literal> or <literal>delete_differ</literal>
+      conflicts, or if the key value conflicts with the remote tuple in cases
+      of <literal>insert_exists</literal> or <literal>update_exists</literal>
+      conflicts.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      The <literal>remote tuple</literal> section of the second sentence in the
+      <literal>DETAIL</literal> line includes the new tuple from the remote
+      insert or update operation that caused the conflict. Note that for an
+      update operation, the column value of the new tuple may be NULL if the
+      value is unchanged.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      The <literal>replica identity</literal> section of the second sentence in
+      the <literal>DETAIL</literal> line includes the replica identity key
+      values that used to search for the existing local tuple to be updated or
+      deleted. This may include the full tuple value if the local relation is
+      marked with <literal>REPLICA IDENTITY FULL</literal>.
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+
   <para>
    Logical replication operations are performed with the privileges of the role
    which owns the subscription.  Permissions failures on target tables will
-- 
2.30.0.windows.2