repeated decoding of prepared transactions

From 129947ab2d0ba223862ed1c87be0f96b51645ba0 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Thu, 18 Feb 2021 20:18:16 -0500
Subject: [PATCH] Don't allow repeated decoding of prepared transactions.

Enforce full snapshot while decoding with two-phase enabled. This
allows the decoder to differentiate between prepared transaction that
were sent prior to restart and prepared transactions that were not sent
because they were prior to consistent snapshot.
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 src/backend/replication/logical/decode.c           |  5 ++-
 src/backend/replication/logical/logical.c          |  8 +++++
 src/backend/replication/logical/reorderbuffer.c    | 15 +++++++++
 src/backend/replication/logical/snapbuild.c        |  9 +++++
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/snapbuild.h                |  1 +
 8 files changed, 53 insertions(+), 52 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..c51870f 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..00d789d 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -789,10 +789,13 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 * SnapBuildProcessRunningXacts. But we need to process cache
 	 * invalidations if there are any for the reasons mentioned in
 	 * DecodeCommit.
+	 *
+	 * We need to mark the transaction as prepared, so that we don't resend it on 
+	 * COMMIT PREPARED.
 	 */
 	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
+		ReorderBufferMarkPrepare(ctx->reorder, xid);
 		ReorderBufferInvalidate(ctx->reorder, xid, buf->origptr);
 		return;
 	}
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 0977aec..d98bc92 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -431,6 +431,10 @@ CreateInitDecodingContext(const char *plugin,
 		startup_cb_wrapper(ctx, &ctx->options, true);
 	MemoryContextSwitchTo(old_context);
 
+	/* If two-phase is on, then only full snapshot can be used */
+	if (ctx->twophase)
+		SetSnapBuildType(ctx->snapshot_builder, true);
+
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
 	return ctx;
@@ -534,6 +538,10 @@ CreateDecodingContext(XLogRecPtr start_lsn,
 
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
+	/* If two-phase is on, then only full snapshot can be used */
+	if (ctx->twophase)
+		SetSnapBuildType(ctx->snapshot_builder, true);
+
 	ereport(LOG,
 			(errmsg("starting logical decoding for slot \"%s\"",
 					NameStr(slot->data.name)),
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 5a62ab8..4730cf0 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2638,6 +2638,21 @@ ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
 	txn->txn_flags |= RBTXN_SKIPPED_PREPARE;
 }
 
+/* Mark this transaction as prepared */
+void
+ReorderBufferMarkPrepare(ReorderBuffer *rb, TransactionId xid)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
+
+	/* unknown transaction, nothing to do */
+	if (txn == NULL)
+		return;
+
+	txn->txn_flags |= RBTXN_PREPARE;
+}
+
 /*
  * Prepare a two-phase transaction.
  *
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 752cf2d..5e6899e 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -357,6 +357,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Set snapshot type
+ */
+void
+SetSnapBuildType(SnapBuild *builder, bool need_full_snapshot)
+{
+	builder->building_full_snapshot = need_full_snapshot;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..8824e60 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -676,6 +676,7 @@ bool		ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 											 TimestampTz prepare_time,
 											 RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid);
+void		ReorderBufferMarkPrepare(ReorderBuffer *rb, TransactionId xid);
 void		ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid, char *gid);
 ReorderBufferTXN *ReorderBufferGetOldestTXN(ReorderBuffer *);
 TransactionId ReorderBufferGetOldestXmin(ReorderBuffer *rb);
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..786d0d4 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -69,6 +69,7 @@ extern void SnapBuildSnapDecRefcount(Snapshot snap);
 extern Snapshot SnapBuildInitialSnapshot(SnapBuild *builder);
 extern const char *SnapBuildExportSnapshot(SnapBuild *snapstate);
 extern void SnapBuildClearExportedSnapshot(void);
+extern void SetSnapBuildType(SnapBuild *builder, bool need_full_snapshot);
 
 extern SnapBuildState SnapBuildCurrentState(SnapBuild *snapstate);
 extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
-- 
1.8.3.1

From ed03c463175733072edf8afb8d120a1285a3194f Mon Sep 17 00:00:00 2001
From: Markus Wanner <markus.wanner@enterprisedb.com>
Date: Tue, 9 Feb 2021 16:16:13 +0100
Subject: [PATCH] Preserve ordering of PREPAREs vs COMMITs in logical decoding

Decouple decoding of the prepare phase of a two-phase transaction from
the final commit (or rollback) of a two-phase transaction, so that
these are more like atomic operations which preserve the ordering in
WAL.  And so that transactional changes of a PREPARE are not ever
provided to the output plugin unnecessarily.

Correct test expectations to expect no duplication.  Add a variant with
a ROLLBACK PREPARED to twophase_snapshot and illustrate the test case
with an explanatory diagram.
---
 contrib/test_decoding/expected/twophase.out   | 38 ++++---------
 .../expected/twophase_snapshot.out            | 40 ++++++++++++-
 .../expected/twophase_stream.out              | 28 +---------
 .../specs/twophase_snapshot.spec              | 56 ++++++++++++++++---
 doc/src/sgml/logicaldecoding.sgml             | 17 ++++--
 .../replication/logical/reorderbuffer.c       | 29 ----------
 6 files changed, 112 insertions(+), 96 deletions(-)

diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 5a62ab8bbc1..d0d805e5c0e 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2695,35 +2695,6 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	/* add the gid in the txn */
 	txn->gid = pstrdup(gid);
 
-	/*
-	 * It is possible that this transaction is not decoded at prepare time
-	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
-	 */
-	if (!rbtxn_prepared(txn) && is_commit)
-	{
-		txn->txn_flags |= RBTXN_PREPARE;
-
-		/*
-		 * The prepare info must have been updated in txn even if we skip
-		 * prepare.
-		 */
-		Assert(txn->final_lsn != InvalidXLogRecPtr);
-
-		/*
-		 * By this time the txn has the prepare record information and it is
-		 * important to use that so that downstream gets the accurate
-		 * information. If instead, we have passed commit information here
-		 * then downstream can behave as it has already replayed commit
-		 * prepared after the restart.
-		 */
-		ReorderBufferReplay(txn, rb, xid, txn->final_lsn, txn->end_lsn,
-							txn->commit_time, txn->origin_id, txn->origin_lsn);
-	}
-
 	txn->final_lsn = commit_lsn;
 	txn->end_lsn = end_lsn;
 	txn->commit_time = commit_time;
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index cf705ed9cda..15820883a43 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -821,11 +821,18 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       whenever the start of a prepared transaction has been decoded. The
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter can be used in this callback to
-      check if the plugin has already received this prepare in which case it
-      can skip the remaining changes of the transaction. This can only happen
-      if the user restarts the decoding after receiving the prepare for a
-      transaction but before receiving the commit prepared say because of some
-      error.
+      identify the transaction and later match it with invocations of
+      of <function>commit_prepared_cb</function>
+      or <function>rollback_prepared_cb</function>.
+     </para>
+
+     <para>
+      Note the start of a logical slot (by LSN) may fall in between
+      a <command>PREPARE</command> and its final <command>COMMIT
+      PREPARED</command> for the same transaction.  Similarly it is possible
+      for a decoder to restart in between.  Therefore, an output plugin needs
+      to be prepared to handle a final commit or rollback for a gid it has not
+      ever seen in its lifetime.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bedd1cf..c51870f8dd1 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d93876462..0b51ead97f7 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -32,10 +32,44 @@ step s2cp: COMMIT PREPARED 'test1';
 step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
 data           
 
-BEGIN          
-table public.do_write: INSERT: id[integer]:1
-PREPARE TRANSACTION 'test1'
 COMMIT PREPARED 'test1'
 ?column?       
 
 stop           
+
+starting permutation: s2b s2txid s1init s3b s3txid s2c s2b s2insert s2p s3c s1insert s1start s2rp s1start
+step s2b: BEGIN;
+step s2txid: SELECT pg_current_xact_id() IS NULL;
+?column?       
+
+f              
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s3b: BEGIN;
+step s3txid: SELECT pg_current_xact_id() IS NULL;
+?column?       
+
+f              
+step s2c: COMMIT;
+step s2b: BEGIN;
+step s2insert: INSERT INTO do_write DEFAULT VALUES;
+step s2p: PREPARE TRANSACTION 'test1';
+step s3c: COMMIT;
+step s1init: <... completed>
+?column?       
+
+init           
+step s1insert: INSERT INTO do_write DEFAULT VALUES;
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+data           
+
+BEGIN          
+table public.do_write: INSERT: id[integer]:2
+COMMIT         
+step s2rp: ROLLBACK PREPARED 'test1';
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+data           
+
+ROLLBACK PREPARED 'test1'
+?column?       
+
+stop           
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd365..d54e640b409 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e700404e0e..f4df24e7353 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -28,6 +28,7 @@ step "s2c" { COMMIT; }
 step "s2insert" { INSERT INTO do_write DEFAULT VALUES; }
 step "s2p" { PREPARE TRANSACTION 'test1'; }
 step "s2cp" { COMMIT PREPARED 'test1'; }
+step "s2rp" { ROLLBACK PREPARED 'test1'; }
 
 
 session "s3"
@@ -37,17 +38,56 @@ step "s3b" { BEGIN; }
 step "s3txid" { SELECT pg_current_xact_id() IS NULL; }
 step "s3c" { COMMIT; }
 
-# Force building of a consistent snapshot between a PREPARE and COMMIT PREPARED
-# and ensure that the whole transaction is decoded at the time of COMMIT
-# PREPARED.
+# Force building of a consistent snapshot between a PREPARE and COMMIT
+# PREPARED, where the changes together with the prepare are decoded
+# while the transaction still is in progress at the point in time the
+# consistent snapshot was taken.
 #
 # 's1init' step will initialize the replication slot and cause logical decoding
 # to wait in initial starting point till the in-progress transaction in s2 is
 # committed. 's2c' step will cause logical decoding to go to initial consistent
 # point and wait for in-progress transaction s3 to commit. 's3c' step will cause
-# logical decoding to find a consistent point while the transaction s2 is
-# prepared and not yet committed. This will cause the first s1start to skip
-# prepared transaction s2 as that will be before consistent point. The second
-# s1start will allow decoding of skipped prepare along with commit prepared done
-# as part of s2cp.
+# logical decoding to find a consistent point while the transaction in s2 is
+# prepared but not yet committed.
+#
+# In this case, the prepare of the two-phase transaction is considered
+# to have happened prior to the creation of the logical slot.  A
+# replica or any kind of consumer that is synchronized up to this
+# specific point in time should already know about that prepared
+# transaction (by gid) and be ready to process a final "commit
+# prepared" or "rollback prepared" for it.
+#
+# The following diagram shows the timeline of events.  The '|' (pipe)
+# stands for a transaction in progress that's neither committed nor
+# prepared, while '.' (dot) stands for a prepared, but still
+# uncommitted transaction.
+#
+#              s2b
+#   s1init      |            <---- Start to state SNAPBUILD_BUILDING_SNAPSHOT with
+#     |         |                  one transaction in progress (by s2).
+#     |         |       s3b
+#     |         |        |         The commit in s2 allows s1 to enter
+#     |        s2c       |   <---- SNAPBUILD_FULL_SNAPSHOT with a different
+#     |                  |         transaction still in progress (by s3).
+#     |        s2b       |
+#     |      s2insert    |         The two-phase transaction to test started in s2,
+#     |         |        |   <---- so s2 and s3 now both have a transaction in
+#     |        s2p       |         progress.
+#     |         .        |
+#     |         .       s3c        Immediately after the commit in s3, s1 is allowed
+#     o         .            <---- to proceed to SNAPSHOT_CONSISTENT and terminate
+#               .                  the creation of the logical slot.
+#               .
+#               .                  minimal transaction by s1, the first that starts
+#  s1insert     .            <---- after the slot creation has completed, the
+#               .                  prepared transaction in s2 still in progress
+#  s1start      .
+#              s2cp                since the transaction in s2 started before
+#  s1start                   <---- the consistent point, none of its changes must be
+#                                  decoded.  The final commit prepared must still
+#                                  be delivered.
+
 permutation "s2b" "s2txid" "s1init" "s3b" "s3txid" "s2c" "s2b" "s2insert" "s2p" "s3c" "s1insert" "s1start" "s2cp" "s1start"
+
+# Equivalent test case with ROLLBACK PREPARED instead.
+permutation "s2b" "s2txid" "s1init" "s3b" "s3txid" "s2c" "s2b" "s2insert" "s2p" "s3c" "s1insert" "s1start" "s2rp" "s1start"
-- 
2.30.0

From fb03795b01583a6d26ded9674f4e2173b16d7cd8 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Tue, 23 Feb 2021 23:13:53 -0500
Subject: [PATCH v1] Avoid repeated decoding of prepared transactions.

Prepared transactions were decoded again after a restart on COMMIT PREPARED
when two-phase commits were enabled. This was done to avoid missing a prepared
transaction that is not part of initial snapshot. Now, this missing PREPARE is identified
by defining a new LSN called snapshot_was_exported_at_lsn and stored in the
slot and snapbuild structures. Prepared transactions that were prior this LSN
will be replayed on a COMMIT PREPARED.

This commit also changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 72 +++++++++-------------
 .../test_decoding/expected/twophase_snapshot.out   |  6 +-
 contrib/test_decoding/expected/twophase_stream.out | 38 +++---------
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +-
 contrib/test_decoding/sql/twophase.sql             | 34 +++++-----
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +--
 contrib/test_decoding/test_decoding.c              | 18 ++----
 doc/src/sgml/logicaldecoding.sgml                  | 15 ++---
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/decode.c           | 11 +++-
 src/backend/replication/logical/logical.c          | 13 +++-
 src/backend/replication/logical/logicalfuncs.c     |  8 +++
 src/backend/replication/logical/reorderbuffer.c    | 28 ++-------
 src/backend/replication/logical/snapbuild.c        | 19 +++++-
 src/backend/replication/repl_gram.y                | 14 ++++-
 src/backend/replication/repl_scanner.l             |  1 +
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 10 ++-
 src/backend/replication/walsender.c                |  6 +-
 src/include/catalog/pg_proc.dat                    |  8 +--
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/reorderbuffer.h            |  2 +
 src/include/replication/slot.h                     | 14 ++++-
 src/include/replication/snapbuild.h                |  4 +-
 24 files changed, 178 insertions(+), 162 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..8d61107 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,21 +32,17 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -55,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -78,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -93,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -102,19 +98,16 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -146,7 +139,7 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -158,15 +151,11 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -178,7 +167,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -188,28 +177,25 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -222,7 +208,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,33 +59,11 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -103,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -111,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index 894e4f5..17ada0f 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -71,11 +71,11 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -87,26 +87,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..28c876d 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,12 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
+
+	/*
+	 * Disable two-phase here, it will be set in the core if it was
+	 * enabled whole creating the slot.
+	 */
+	ctx->twophase = false;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index cf705ed..562a7cb 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -179,7 +179,7 @@ postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +188,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -201,7 +201,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -210,7 +210,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
@@ -822,10 +822,7 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter can be used in this callback to
       check if the plugin has already received this prepare in which case it
-      can skip the remaining changes of the transaction. This can only happen
-      if the user restarts the decoding after receiving the prepare for a
-      transaction but before receiving the commit prepared say because of some
-      error.
+      can either error out or skip the remaining changes of the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..f6c5fc5 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1318,6 +1318,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..1be4715 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -663,6 +663,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	XLogRecPtr	origin_lsn = InvalidXLogRecPtr;
 	TimestampTz commit_time = parsed->xact_time;
 	RepOriginId origin_id = XLogRecGetOrigin(buf->record);
+	XLogRecPtr  snapshot_was_exported_at_lsn = InvalidXLogRecPtr;
 	int			i;
 
 	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
@@ -715,7 +716,14 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (two_phase)
 	{
+		/*
+		 * Get the LSN at which the snapshot for this slot was exported.
+		 * ReorderBufferFinishPrepared will decide based on this if the
+		 * transaction should be replayed on COMMIT PREPARED.
+		 */
+		snapshot_was_exported_at_lsn = SnapBuildExportLSNAt(ctx->snapshot_builder);
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									snapshot_was_exported_at_lsn,
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -774,7 +782,6 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	/* We can't start streaming unless a consistent state is reached. */
 	if (SnapBuildCurrentState(builder) < SNAPBUILD_CONSISTENT)
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		return;
 	}
 
@@ -792,7 +799,6 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		ReorderBufferInvalidate(ctx->reorder, xid, buf->origptr);
 		return;
 	}
@@ -854,6 +860,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..8555f5e 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.snapshot_was_exported_at_lsn);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,17 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+
+	/*
+	 * The snapshot_was_exported_at_lsn point is required in two-phase
+	 * commits to handle prepared transactions that were not part of this
+	 * snapshot at export time. PREPAREs prior to this point need special
+	 * handling if two-phase commits are enabled.
+	 * The snapshot_was_exported_at_lsn is only updated once when
+	 * the slot is created and is not modified on restarts unlike the
+	 * confirmed_flush point.
+	 */
+	slot->data.snapshot_was_exported_at_lsn = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index f7e0558..4a919d1 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -239,6 +239,14 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 									LogicalOutputPrepareWrite,
 									LogicalOutputWrite, NULL);
 
+		/* If twophase is set on the slot at create time, then
+		 * make sure the field in the context is also updated
+		 */
+		if (MyReplicationSlot->data.twophase)
+		{
+			ctx->twophase = true;
+		}
+
 		/*
 		 * After the sanity checks in CreateDecodingContext, make sure the
 		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..9a95a15 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2623,21 +2623,6 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 	return true;
 }
 
-/* Remember that we have skipped prepare */
-void
-ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
-{
-	ReorderBufferTXN *txn;
-
-	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
-
-	/* unknown transaction, nothing to do */
-	if (txn == NULL)
-		return;
-
-	txn->txn_flags |= RBTXN_SKIPPED_PREPARE;
-}
-
 /*
  * Prepare a two-phase transaction.
  *
@@ -2672,6 +2657,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr snapshot_was_exported_at_lsn,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2696,14 +2682,12 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	txn->gid = pstrdup(gid);
 
 	/*
-	 * It is possible that this transaction is not decoded at prepare time
-	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * It is possible that this transaction was not decoded at prepare time
+	 * because by that time we didn't have a consistent snapshot.
+	 * In which case we need to replay the prepared transaction here because
+	 * downstream would not have seen this transaction yet.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < snapshot_was_exported_at_lsn) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..7622b1d 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,12 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * In two-phase commits, if the PREPARE is prior to this LSN, then the
+	 * whole transaction needs to be replayed at COMMIT PREPARED.
+	 */
+	XLogRecPtr  snapshot_was_exported_at_lsn;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +275,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr snapshot_was_exported_at_lsn)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +304,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->snapshot_was_exported_at_lsn = snapshot_was_exported_at_lsn;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +365,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildExportLSNAt(SnapBuild *builder)
+{
+	return builder->snapshot_was_exported_at_lsn;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index eb283a8..aeec791 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -84,6 +84,7 @@ static SQLCmd *make_sqlcmd(void);
 %token K_SLOT
 %token K_RESERVE_WAL
 %token K_TEMPORARY
+%token K_TWOPHASE
 %token K_EXPORT_SNAPSHOT
 %token K_NOEXPORT_SNAPSHOT
 %token K_USE_SNAPSHOT
@@ -102,6 +103,7 @@ static SQLCmd *make_sqlcmd(void);
 %type <node>	plugin_opt_arg
 %type <str>		opt_slot var_name
 %type <boolval>	opt_temporary
+%type <boolval>	opt_twophase
 %type <list>	create_slot_opt_list
 %type <defelt>	create_slot_opt
 
@@ -242,15 +244,16 @@ create_replication_slot:
 					$$ = (Node *) cmd;
 				}
 			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin */
-			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list
+			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary opt_twophase K_LOGICAL IDENT create_slot_opt_list
 				{
 					CreateReplicationSlotCmd *cmd;
 					cmd = makeNode(CreateReplicationSlotCmd);
 					cmd->kind = REPLICATION_KIND_LOGICAL;
 					cmd->slotname = $2;
 					cmd->temporary = $3;
-					cmd->plugin = $5;
-					cmd->options = $6;
+					cmd->twophase = $4;
+					cmd->plugin = $6;
+					cmd->options = $7;
 					$$ = (Node *) cmd;
 				}
 			;
@@ -365,6 +368,11 @@ opt_temporary:
 			| /* EMPTY */					{ $$ = false; }
 			;
 
+opt_twophase:
+			K_TWOPHASE						{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
 opt_slot:
 			K_SLOT IDENT
 				{ $$ = $2; }
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index dcc3c3f..3032c28 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -103,6 +103,7 @@ RESERVE_WAL			{ return K_RESERVE_WAL; }
 LOGICAL				{ return K_LOGICAL; }
 SLOT				{ return K_SLOT; }
 TEMPORARY			{ return K_TEMPORARY; }
+TWOPHASE			{ return K_TWOPHASE; }
 EXPORT_SNAPSHOT		{ return K_EXPORT_SNAPSHOT; }
 NOEXPORT_SNAPSHOT	{ return K_NOEXPORT_SNAPSHOT; }
 USE_SNAPSHOT		{ return K_USE_SNAPSHOT; }
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..38c385b 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool twophase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.twophase    = twophase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..a441fa4 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool twophase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, twophase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		twophase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									twophase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -796,6 +799,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8124454..9146e62 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -937,7 +937,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -951,7 +952,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->twophase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1604412..8459488 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10502,10 +10502,10 @@
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..1a933e2 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		twophase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..e1842c0 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr snapshot_consistency_lsn,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
@@ -676,6 +677,7 @@ bool		ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 											 TimestampTz prepare_time,
 											 RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid);
+void		ReorderBufferMarkPrepare(ReorderBuffer *rb, TransactionId xid);
 void		ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid, char *gid);
 ReorderBufferTXN *ReorderBufferGetOldestTXN(ReorderBuffer *);
 TransactionId ReorderBufferGetOldestXmin(ReorderBuffer *rb);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..9452604 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,18 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which this slot found consistent point and snapshot exported.
+	 * This is required for two-phase transactions to decide if the whole
+	 * transaction should be replayed at COMMIT PREPARED.
+	 */
+	XLogRecPtr  snapshot_was_exported_at_lsn;
+
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        twophase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -192,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool twophase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..0693115 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr snapshot_was_exported_at_lsn);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildExportLSNAt(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
1.8.3.1

From 017c25df53759f3a88a96b73e2240cfba444d4b4 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Wed, 24 Feb 2021 04:34:40 -0500
Subject: [PATCH v2] Avoid repeated decoding of prepared transactions.

Prepared transactions were decoded again after a restart on COMMIT PREPARED
when two-phase commits were enabled. This was done to avoid missing a prepared
transaction that is not part of initial snapshot. Now, this missing PREPARE is identified
by defining a new LSN called snapshot_was_exported_at_lsn and stored in the
slot and snapbuild structures. Prepared transactions that were prior this LSN
will be replayed on a COMMIT PREPARED.
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 src/backend/replication/logical/decode.c           | 11 +++++--
 src/backend/replication/logical/logical.c          | 13 +++++++-
 src/backend/replication/logical/reorderbuffer.c    | 28 ++++------------
 src/backend/replication/logical/snapbuild.c        | 19 ++++++++++-
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/slot.h                     |  7 ++++
 src/include/replication/snapbuild.h                |  4 ++-
 9 files changed, 71 insertions(+), 78 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..c51870f 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..9f6e5d5 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -663,6 +663,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	XLogRecPtr	origin_lsn = InvalidXLogRecPtr;
 	TimestampTz commit_time = parsed->xact_time;
 	RepOriginId origin_id = XLogRecGetOrigin(buf->record);
+	XLogRecPtr  snapshot_was_exported_at_lsn = InvalidXLogRecPtr;
 	int			i;
 
 	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
@@ -715,7 +716,14 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (two_phase)
 	{
+		/*
+		 * Get the LSN at which the snapshot for this slot was exported.
+		 * ReorderBufferFinishPrepared will decide based on this if the
+		 * transaction should be replayed on COMMIT PREPARED.
+		 */
+		snapshot_was_exported_at_lsn = SnapBuildExportLSNAt(ctx->snapshot_builder);
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									snapshot_was_exported_at_lsn,
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -774,7 +782,6 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	/* We can't start streaming unless a consistent state is reached. */
 	if (SnapBuildCurrentState(builder) < SNAPBUILD_CONSISTENT)
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		return;
 	}
 
@@ -792,7 +799,6 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		ReorderBufferInvalidate(ctx->reorder, xid, buf->origptr);
 		return;
 	}
@@ -854,6 +860,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..5634635 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.snapshot_was_exported_at_lsn);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,17 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+
+	/*
+	 * The snapshot_was_exported_at_lsn point is required in two-phase
+	 * commits to handle prepared transactions that were not part of this
+	 * snapshot at export time. PREPAREs prior to this point need special
+	 * handling if two-phase commits are enabled.
+	 * The snapshot_was_exported_at_lsn is only updated once when
+	 * the slot is created and is not modified on restarts unlike the
+	 * confirmed_flush point.
+	 */
+	slot->data.snapshot_was_exported_at_lsn = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..5a3c986 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2623,21 +2623,6 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 	return true;
 }
 
-/* Remember that we have skipped prepare */
-void
-ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
-{
-	ReorderBufferTXN *txn;
-
-	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
-
-	/* unknown transaction, nothing to do */
-	if (txn == NULL)
-		return;
-
-	txn->txn_flags |= RBTXN_SKIPPED_PREPARE;
-}
-
 /*
  * Prepare a two-phase transaction.
  *
@@ -2672,6 +2657,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr snapshot_was_exported_at_lsn,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2696,14 +2682,12 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	txn->gid = pstrdup(gid);
 
 	/*
-	 * It is possible that this transaction is not decoded at prepare time
-	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * It is possible that this transaction was not decoded at prepare time
+	 * because by that time we didn't have a consistent snapshot.
+	 * In which case we need to replay the prepared transaction here because
+	 * downstream would not have seen this transaction yet.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < snapshot_was_exported_at_lsn) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..7622b1d 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,12 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * In two-phase commits, if the PREPARE is prior to this LSN, then the
+	 * whole transaction needs to be replayed at COMMIT PREPARED.
+	 */
+	XLogRecPtr  snapshot_was_exported_at_lsn;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +275,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr snapshot_was_exported_at_lsn)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +304,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->snapshot_was_exported_at_lsn = snapshot_was_exported_at_lsn;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +365,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildExportLSNAt(SnapBuild *builder)
+{
+	return builder->snapshot_was_exported_at_lsn;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..1dbb50e 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr snapshot_consistency_lsn,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..ad8fb37 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,13 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which this slot found consistent point and snapshot exported.
+	 * This is required for two-phase transactions to decide if the whole
+	 * transaction should be replayed at COMMIT PREPARED.
+	 */
+	XLogRecPtr  snapshot_was_exported_at_lsn;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..0693115 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr snapshot_was_exported_at_lsn);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildExportLSNAt(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
1.8.3.1

From a5ad5f7789532f70833e0d1fe54c232c5e2ff9bd Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Wed, 24 Feb 2021 05:53:14 -0500
Subject: [PATCH v2] Add option to enable two-phase commits in
 pg_create_logical_replication_slot

This commit changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 18 ++++--------
 doc/src/sgml/logicaldecoding.sgml                  | 19 +++++-------
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/logicalfuncs.c     |  8 +++++
 src/backend/replication/repl_gram.y                | 14 +++++++--
 src/backend/replication/repl_scanner.l             |  1 +
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 10 +++++--
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    |  8 ++---
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 18 files changed, 108 insertions(+), 86 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index c51870f..8d61107 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -139,7 +139,7 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -151,7 +151,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -167,7 +167,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -177,7 +177,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -188,14 +188,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -208,7 +208,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index 894e4f5..17ada0f 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -71,11 +71,11 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -87,26 +87,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..28c876d 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,12 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
+
+	/*
+	 * Disable two-phase here, it will be set in the core if it was
+	 * enabled whole creating the slot.
+	 */
+	ctx->twophase = false;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 6455664..019a440 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -179,7 +179,7 @@ postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +188,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -201,7 +201,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -210,7 +210,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
@@ -820,12 +820,9 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       The required <function>begin_prepare_cb</function> callback is called
       whenever the start of a prepared transaction has been decoded. The
       <parameter>gid</parameter> field, which is part of the
-      <parameter>txn</parameter> parameter, can be used in this callback to
-      check if the plugin has already received this <command>PREPARE</command>
-      in which case it can skip the remaining changes of the transaction.
-      This can only happen if the user restarts the decoding after receiving
-      the <command>PREPARE</command> for a transaction but before receiving
-      the <command>COMMIT PREPARED</command>, say because of some error.
+      <parameter>txn</parameter> parameter can be used in this callback to
+      check if the plugin has already received this prepare in which case it
+      can either error out or skip the remaining changes of the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..f6c5fc5 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1318,6 +1318,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index f7e0558..4a919d1 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -239,6 +239,14 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 									LogicalOutputPrepareWrite,
 									LogicalOutputWrite, NULL);
 
+		/* If twophase is set on the slot at create time, then
+		 * make sure the field in the context is also updated
+		 */
+		if (MyReplicationSlot->data.twophase)
+		{
+			ctx->twophase = true;
+		}
+
 		/*
 		 * After the sanity checks in CreateDecodingContext, make sure the
 		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index eb283a8..aeec791 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -84,6 +84,7 @@ static SQLCmd *make_sqlcmd(void);
 %token K_SLOT
 %token K_RESERVE_WAL
 %token K_TEMPORARY
+%token K_TWOPHASE
 %token K_EXPORT_SNAPSHOT
 %token K_NOEXPORT_SNAPSHOT
 %token K_USE_SNAPSHOT
@@ -102,6 +103,7 @@ static SQLCmd *make_sqlcmd(void);
 %type <node>	plugin_opt_arg
 %type <str>		opt_slot var_name
 %type <boolval>	opt_temporary
+%type <boolval>	opt_twophase
 %type <list>	create_slot_opt_list
 %type <defelt>	create_slot_opt
 
@@ -242,15 +244,16 @@ create_replication_slot:
 					$$ = (Node *) cmd;
 				}
 			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin */
-			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list
+			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary opt_twophase K_LOGICAL IDENT create_slot_opt_list
 				{
 					CreateReplicationSlotCmd *cmd;
 					cmd = makeNode(CreateReplicationSlotCmd);
 					cmd->kind = REPLICATION_KIND_LOGICAL;
 					cmd->slotname = $2;
 					cmd->temporary = $3;
-					cmd->plugin = $5;
-					cmd->options = $6;
+					cmd->twophase = $4;
+					cmd->plugin = $6;
+					cmd->options = $7;
 					$$ = (Node *) cmd;
 				}
 			;
@@ -365,6 +368,11 @@ opt_temporary:
 			| /* EMPTY */					{ $$ = false; }
 			;
 
+opt_twophase:
+			K_TWOPHASE						{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
 opt_slot:
 			K_SLOT IDENT
 				{ $$ = $2; }
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index dcc3c3f..3032c28 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -103,6 +103,7 @@ RESERVE_WAL			{ return K_RESERVE_WAL; }
 LOGICAL				{ return K_LOGICAL; }
 SLOT				{ return K_SLOT; }
 TEMPORARY			{ return K_TEMPORARY; }
+TWOPHASE			{ return K_TWOPHASE; }
 EXPORT_SNAPSHOT		{ return K_EXPORT_SNAPSHOT; }
 NOEXPORT_SNAPSHOT	{ return K_NOEXPORT_SNAPSHOT; }
 USE_SNAPSHOT		{ return K_USE_SNAPSHOT; }
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..38c385b 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool twophase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.twophase    = twophase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..a441fa4 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool twophase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, twophase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		twophase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									twophase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -796,6 +799,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8124454..9146e62 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -937,7 +937,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -951,7 +952,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->twophase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1604412..8459488 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10502,10 +10502,10 @@
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..1a933e2 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		twophase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index ad8fb37..9452604 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -98,6 +98,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr  snapshot_was_exported_at_lsn;
 
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        twophase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -199,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool twophase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
-- 
1.8.3.1

From b939268386b82214b8a8fcc968885ba90f4e12fd Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Wed, 24 Feb 2021 04:34:40 -0500
Subject: [PATCH v3 1/2] Avoid repeated decoding of prepared transactions.

Prepared transactions were decoded again after a restart on COMMIT PREPARED
when two-phase commits were enabled. This was done to avoid missing a prepared
transaction that is not part of initial snapshot. Now, this missing PREPARE is identified
by defining a new LSN called snapshot_was_exported_at_lsn and stored in the
slot and snapbuild structures. Prepared transactions that were prior this LSN
will be replayed on a COMMIT PREPARED.
---
 contrib/test_decoding/expected/twophase.out   | 38 ++++++-------------
 .../expected/twophase_stream.out              | 28 ++------------
 src/backend/replication/logical/decode.c      | 11 +++++-
 src/backend/replication/logical/logical.c     | 13 ++++++-
 .../replication/logical/reorderbuffer.c       | 28 +++-----------
 src/backend/replication/logical/snapbuild.c   | 19 +++++++++-
 src/include/replication/reorderbuffer.h       |  1 +
 src/include/replication/slot.h                |  7 ++++
 src/include/replication/snapbuild.h           |  4 +-
 9 files changed, 71 insertions(+), 78 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bedd1c..c51870f8dd 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd36..d54e640b40 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df00d0..9f6e5d52ab 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -663,6 +663,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	XLogRecPtr	origin_lsn = InvalidXLogRecPtr;
 	TimestampTz commit_time = parsed->xact_time;
 	RepOriginId origin_id = XLogRecGetOrigin(buf->record);
+	XLogRecPtr  snapshot_was_exported_at_lsn = InvalidXLogRecPtr;
 	int			i;
 
 	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
@@ -715,7 +716,14 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (two_phase)
 	{
+		/*
+		 * Get the LSN at which the snapshot for this slot was exported.
+		 * ReorderBufferFinishPrepared will decide based on this if the
+		 * transaction should be replayed on COMMIT PREPARED.
+		 */
+		snapshot_was_exported_at_lsn = SnapBuildExportLSNAt(ctx->snapshot_builder);
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									snapshot_was_exported_at_lsn,
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -774,7 +782,6 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	/* We can't start streaming unless a consistent state is reached. */
 	if (SnapBuildCurrentState(builder) < SNAPBUILD_CONSISTENT)
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		return;
 	}
 
@@ -792,7 +799,6 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
 	{
-		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		ReorderBufferInvalidate(ctx->reorder, xid, buf->origptr);
 		return;
 	}
@@ -854,6 +860,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45ff43..5634635e94 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.snapshot_was_exported_at_lsn);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,17 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+
+	/*
+	 * The snapshot_was_exported_at_lsn point is required in two-phase
+	 * commits to handle prepared transactions that were not part of this
+	 * snapshot at export time. PREPAREs prior to this point need special
+	 * handling if two-phase commits are enabled.
+	 * The snapshot_was_exported_at_lsn is only updated once when
+	 * the slot is created and is not modified on restarts unlike the
+	 * confirmed_flush point.
+	 */
+	slot->data.snapshot_was_exported_at_lsn = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b963211e..5a3c986c85 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2623,21 +2623,6 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 	return true;
 }
 
-/* Remember that we have skipped prepare */
-void
-ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
-{
-	ReorderBufferTXN *txn;
-
-	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
-
-	/* unknown transaction, nothing to do */
-	if (txn == NULL)
-		return;
-
-	txn->txn_flags |= RBTXN_SKIPPED_PREPARE;
-}
-
 /*
  * Prepare a two-phase transaction.
  *
@@ -2672,6 +2657,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr snapshot_was_exported_at_lsn,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2696,14 +2682,12 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	txn->gid = pstrdup(gid);
 
 	/*
-	 * It is possible that this transaction is not decoded at prepare time
-	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * It is possible that this transaction was not decoded at prepare time
+	 * because by that time we didn't have a consistent snapshot.
+	 * In which case we need to replay the prepared transaction here because
+	 * downstream would not have seen this transaction yet.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < snapshot_was_exported_at_lsn) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e11788795f..7622b1dba1 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -164,6 +164,12 @@ struct SnapBuild
 	 */
 	XLogRecPtr	start_decoding_at;
 
+	/*
+	 * In two-phase commits, if the PREPARE is prior to this LSN, then the
+	 * whole transaction needs to be replayed at COMMIT PREPARED.
+	 */
+	XLogRecPtr  snapshot_was_exported_at_lsn;
+
 	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
@@ -269,7 +275,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr snapshot_was_exported_at_lsn)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +304,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->snapshot_was_exported_at_lsn = snapshot_was_exported_at_lsn;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -356,6 +364,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 	return builder->state;
 }
 
+/*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildExportLSNAt(SnapBuild *builder)
+{
+	return builder->snapshot_was_exported_at_lsn;
+}
+
 /*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf7af..1dbb50eb53 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr snapshot_consistency_lsn,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b3fc..ad8fb371a6 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,13 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which this slot found consistent point and snapshot exported.
+	 * This is required for two-phase transactions to decide if the whole
+	 * transaction should be replayed at COMMIT PREPARED.
+	 */
+	XLogRecPtr  snapshot_was_exported_at_lsn;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a58e..0693115005 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr snapshot_was_exported_at_lsn);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildExportLSNAt(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
2.28.0.windows.1

From 7e69b0f926743a3b15233b6c9c5b3436b927cb1d Mon Sep 17 00:00:00 2001
From: Amit Kapila <akapila@postgresql.org>
Date: Thu, 25 Feb 2021 16:46:39 +0530
Subject: [PATCH v3 2/2] Fixed review comments.

---
 src/backend/replication/logical/decode.c      | 11 ++------
 src/backend/replication/logical/logical.c     | 14 ++--------
 .../replication/logical/reorderbuffer.c       | 28 +++++++++++++++----
 src/backend/replication/logical/snapbuild.c   | 18 +++++++-----
 src/include/replication/slot.h                |  7 ++---
 src/include/replication/snapbuild.h           |  4 +--
 6 files changed, 43 insertions(+), 39 deletions(-)

diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index 9f6e5d52ab..7f83bbb6a3 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -663,7 +663,6 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	XLogRecPtr	origin_lsn = InvalidXLogRecPtr;
 	TimestampTz commit_time = parsed->xact_time;
 	RepOriginId origin_id = XLogRecGetOrigin(buf->record);
-	XLogRecPtr  snapshot_was_exported_at_lsn = InvalidXLogRecPtr;
 	int			i;
 
 	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
@@ -716,14 +715,8 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (two_phase)
 	{
-		/*
-		 * Get the LSN at which the snapshot for this slot was exported.
-		 * ReorderBufferFinishPrepared will decide based on this if the
-		 * transaction should be replayed on COMMIT PREPARED.
-		 */
-		snapshot_was_exported_at_lsn = SnapBuildExportLSNAt(ctx->snapshot_builder);
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
-									snapshot_was_exported_at_lsn,
+									SnapBuildExportAt(ctx->snapshot_builder),
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -782,6 +775,7 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	/* We can't start streaming unless a consistent state is reached. */
 	if (SnapBuildCurrentState(builder) < SNAPBUILD_CONSISTENT)
 	{
+		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		return;
 	}
 
@@ -799,6 +793,7 @@ DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	 */
 	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
 	{
+		ReorderBufferSkipPrepare(ctx->reorder, xid);
 		ReorderBufferInvalidate(ctx->reorder, xid, buf->origptr);
 		return;
 	}
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 5634635e94..2ea82c6513 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot, slot->data.snapshot_was_exported_at_lsn);
+								need_full_snapshot, slot->data.snapshot_was_exported_at);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,17 +590,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
-
-	/*
-	 * The snapshot_was_exported_at_lsn point is required in two-phase
-	 * commits to handle prepared transactions that were not part of this
-	 * snapshot at export time. PREPAREs prior to this point need special
-	 * handling if two-phase commits are enabled.
-	 * The snapshot_was_exported_at_lsn is only updated once when
-	 * the slot is created and is not modified on restarts unlike the
-	 * confirmed_flush point.
-	 */
-	slot->data.snapshot_was_exported_at_lsn = ctx->reader->EndRecPtr;
+	slot->data.snapshot_was_exported_at = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 5a3c986c85..8aefc7eaa7 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2623,6 +2623,21 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 	return true;
 }
 
+/* Remember that we have skipped prepare */
+void
+ReorderBufferSkipPrepare(ReorderBuffer* rb, TransactionId xid)
+{
+	ReorderBufferTXN* txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
+
+	/* unknown transaction, nothing to do */
+	if (txn == NULL)
+		return;
+
+	txn->txn_flags |= RBTXN_SKIPPED_PREPARE;
+}
+
 /*
  * Prepare a two-phase transaction.
  *
@@ -2657,7 +2672,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
-							XLogRecPtr snapshot_was_exported_at_lsn,
+							XLogRecPtr snapshot_was_exported_at,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2682,12 +2697,13 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	txn->gid = pstrdup(gid);
 
 	/*
-	 * It is possible that this transaction was not decoded at prepare time
-	 * because by that time we didn't have a consistent snapshot.
-	 * In which case we need to replay the prepared transaction here because
-	 * downstream would not have seen this transaction yet.
+	 * It is possible that this transaction is not decoded at prepare time
+	 * either because by that time we didn't have a consistent snapshot or it
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
 	 */
-	if ((txn->final_lsn < snapshot_was_exported_at_lsn) && is_commit)
+	if ((txn->final_lsn < snapshot_was_exported_at) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 7622b1dba1..fe486c4c83 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,10 +165,14 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
-	 * In two-phase commits, if the PREPARE is prior to this LSN, then the
-	 * whole transaction needs to be replayed at COMMIT PREPARED.
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported snapshot for initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot needs
+	 * to be sent later along with commit prepared and they must be before this
+	 * point.
 	 */
-	XLogRecPtr  snapshot_was_exported_at_lsn;
+	XLogRecPtr  snapshot_was_exported_at;
 
 	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
@@ -276,7 +280,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
 						bool need_full_snapshot,
-						XLogRecPtr snapshot_was_exported_at_lsn)
+						XLogRecPtr snapshot_was_exported_at)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -304,7 +308,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
-	builder->snapshot_was_exported_at_lsn = snapshot_was_exported_at_lsn;
+	builder->snapshot_was_exported_at = snapshot_was_exported_at;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -368,9 +372,9 @@ SnapBuildCurrentState(SnapBuild *builder)
  * Return the LSN at which the snapshot was exported
  */
 XLogRecPtr
-SnapBuildExportLSNAt(SnapBuild *builder)
+SnapBuildExportAt(SnapBuild *builder)
 {
-	return builder->snapshot_was_exported_at_lsn;
+	return builder->snapshot_was_exported_at;
 }
 
 /*
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index ad8fb371a6..5764293555 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -92,11 +92,10 @@ typedef struct ReplicationSlotPersistentData
 	XLogRecPtr	confirmed_flush;
 
 	/*
-	 * LSN at which this slot found consistent point and snapshot exported.
-	 * This is required for two-phase transactions to decide if the whole
-	 * transaction should be replayed at COMMIT PREPARED.
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported snapshot for initial copy.
 	 */
-	XLogRecPtr  snapshot_was_exported_at_lsn;
+	XLogRecPtr  snapshot_was_exported_at;
 
 	/* plugin name */
 	NameData	plugin;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index 0693115005..f15ac6639f 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -62,7 +62,7 @@ extern void CheckPointSnapBuild(void);
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
 										  bool need_full_snapshot,
-										  XLogRecPtr snapshot_was_exported_at_lsn);
+										  XLogRecPtr snapshot_was_exported_at);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -76,7 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
-extern XLogRecPtr SnapBuildExportLSNAt(SnapBuild *builder);
+extern XLogRecPtr SnapBuildExportAt(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
2.28.0.windows.1

From 17ff5462c3c4137796e044e95e609cbe77df673c Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Fri, 26 Feb 2021 02:58:49 -0500
Subject: [PATCH v4] Avoid repeated decoding of prepared transactions.

Prepared transactions were decoded again after a restart on COMMIT PREPARED
when two-phase commits were enabled. This was done to avoid missing a prepared
transaction that is not part of initial snapshot. Now, this missing PREPARE is identified
by defining a new LSN called snapshot_was_exported_at_lsn and stored in the
slot and snapbuild structures. Prepared transactions that were prior this LSN
will be replayed on a COMMIT PREPARED.
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 doc/src/sgml/catalogs.sgml                         | 11 +++++++
 doc/src/sgml/logicaldecoding.sgml                  |  9 ++---
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/decode.c           |  2 ++
 src/backend/replication/logical/logical.c          |  3 +-
 src/backend/replication/logical/reorderbuffer.c    | 14 ++++----
 src/backend/replication/logical/snapbuild.c        | 23 ++++++++++++-
 src/backend/replication/slotfuncs.c                |  7 +++-
 src/include/catalog/pg_proc.dat                    |  6 ++--
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/slot.h                     |  6 ++++
 src/include/replication/snapbuild.h                |  4 ++-
 src/test/regress/expected/rules.out                |  3 +-
 15 files changed, 83 insertions(+), 73 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..c51870f 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index db29905..366a971 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -11479,6 +11479,17 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>snapshot_was_exported_at</structfield> <type>pg_lsn</type>
+      </para>
+      <para>
+       The address (<literal>LSN</literal>) at which the logical
+       slot found a consistent point at the time of slot creation.
+       <literal>NULL</literal> for physical slots.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>wal_status</structfield> <type>text</type>
       </para>
       <para>
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 6455664..18d592d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -191,9 +191,6 @@ postgres=# COMMIT PREPARED 'test_prepared1';
 postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
- 0/1689DC0 | 529 | BEGIN 529
- 0/1689DC0 | 529 | table public.data: INSERT: id[integer]:3 data[text]:'5'
- 0/1689FC0 | 529 | PREPARE TRANSACTION 'test_prepared1', txid 529
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
 (4 row)
 
@@ -822,10 +819,8 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter, can be used in this callback to
       check if the plugin has already received this <command>PREPARE</command>
-      in which case it can skip the remaining changes of the transaction.
-      This can only happen if the user restarts the decoding after receiving
-      the <command>PREPARE</command> for a transaction but before receiving
-      the <command>COMMIT PREPARED</command>, say because of some error.
+      in which case it can either error out or skip the remaining changes of 
+      the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..3f94398 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -893,6 +893,7 @@ CREATE VIEW pg_replication_slots AS
             L.catalog_xmin,
             L.restart_lsn,
             L.confirmed_flush_lsn,
+			L.snapshot_was_exported_at,
             L.wal_status,
             L.safe_wal_size
     FROM pg_get_replication_slots() AS L
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..7f83bbb 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -716,6 +716,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	if (two_phase)
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									SnapBuildExportAt(ctx->snapshot_builder),
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -854,6 +855,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..2ea82c6 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.snapshot_was_exported_at);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+	slot->data.snapshot_was_exported_at = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..8aefc7e 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2625,9 +2625,9 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 
 /* Remember that we have skipped prepare */
 void
-ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
+ReorderBufferSkipPrepare(ReorderBuffer* rb, TransactionId xid)
 {
-	ReorderBufferTXN *txn;
+	ReorderBufferTXN* txn;
 
 	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
 
@@ -2672,6 +2672,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr snapshot_was_exported_at,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2698,12 +2699,11 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	/*
 	 * It is possible that this transaction is not decoded at prepare time
 	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < snapshot_was_exported_at) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..fe486c4 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,16 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported snapshot for initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot needs
+	 * to be sent later along with commit prepared and they must be before this
+	 * point.
+	 */
+	XLogRecPtr  snapshot_was_exported_at;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +279,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr snapshot_was_exported_at)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +308,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->snapshot_was_exported_at = snapshot_was_exported_at;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +369,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildExportAt(SnapBuild *builder)
+{
+	return builder->snapshot_was_exported_at;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..f5efdff 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -236,7 +236,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
-#define PG_GET_REPLICATION_SLOTS_COLS 13
+#define PG_GET_REPLICATION_SLOTS_COLS 14
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	TupleDesc	tupdesc;
 	Tuplestorestate *tupstore;
@@ -344,6 +344,11 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 		else
 			nulls[i++] = true;
 
+		if (slot_contents.data.snapshot_was_exported_at != InvalidXLogRecPtr)
+			values[i++] = LSNGetDatum(slot_contents.data.snapshot_was_exported_at);
+		else
+			nulls[i++] = true;
+
 		/*
 		 * If invalidated_at is valid and restart_lsn is invalid, we know for
 		 * certain that the slot has been invalidated.  Otherwise, test
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1604412..e1e4f3e 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10496,9 +10496,9 @@
   proname => 'pg_get_replication_slots', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size}',
+  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,pg_lsn,text,int8}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,snapshot_was_exported_at,wal_status,safe_wal_size}',
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..1dbb50e 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr snapshot_consistency_lsn,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..5764293 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,12 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported snapshot for initial copy.
+	 */
+	XLogRecPtr  snapshot_was_exported_at;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..f15ac66 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr snapshot_was_exported_at);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildExportAt(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 10a1f34..10647d4 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1476,9 +1476,10 @@ pg_replication_slots| SELECT l.slot_name,
     l.catalog_xmin,
     l.restart_lsn,
     l.confirmed_flush_lsn,
+    l.snapshot_was_exported_at,
     l.wal_status,
     l.safe_wal_size
-   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size)
+   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, snapshot_was_exported_at, wal_status, safe_wal_size)
      LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
 pg_roles| SELECT pg_authid.rolname,
     pg_authid.rolsuper,
-- 
1.8.3.1

From 3c08b2ecda5470d24f595ec920226843563a5a95 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Fri, 26 Feb 2021 05:38:09 -0500
Subject: [PATCH v4] Add option to enable two-phase commits in
 pg_create_logical_replication_slot

This commit changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 18 ++++--------
 doc/src/sgml/logicaldecoding.sgml                  | 19 ++++++------
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/logicalfuncs.c     |  8 +++++
 src/backend/replication/repl_gram.y                | 14 +++++++--
 src/backend/replication/repl_scanner.l             |  1 +
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 10 +++++--
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    |  8 ++---
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 18 files changed, 110 insertions(+), 84 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index c51870f..8d61107 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -139,7 +139,7 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -151,7 +151,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -167,7 +167,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -177,7 +177,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -188,14 +188,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -208,7 +208,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index 894e4f5..17ada0f 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -71,11 +71,11 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -87,26 +87,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..28c876d 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,12 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
+
+	/*
+	 * Disable two-phase here, it will be set in the core if it was
+	 * enabled whole creating the slot.
+	 */
+	ctx->twophase = false;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 18d592d..5839d96 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -169,17 +169,18 @@ $ pg_recvlogical -d postgres --slot=test --drop-slot
   <para>
   The following example shows SQL interface that can be used to decode prepared
   transactions. Before you use two-phase commit commands, you must set
-  <varname>max_prepared_transactions</varname> to at least 1. You must also set
-  the option 'two-phase-commit' to 1 while calling
-  <function>pg_logical_slot_get_changes</function>. Note that we will stream
-  the entire transaction after the commit if it is not already decoded.
+  <varname>max_prepared_transactions</varname> to at least 1. You must also have
+  set the two-phase parameter as 'true' while creating the slot using
+  <function>pg_create_logical_replication_slot</function>
+  Note that we will stream the entire transaction after the commit if it
+  is not already decoded.
   </para>
 <programlisting>
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +189,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
@@ -198,7 +199,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -207,7 +208,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 3f94398..1e61274 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1319,6 +1319,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index f7e0558..4a919d1 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -239,6 +239,14 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 									LogicalOutputPrepareWrite,
 									LogicalOutputWrite, NULL);
 
+		/* If twophase is set on the slot at create time, then
+		 * make sure the field in the context is also updated
+		 */
+		if (MyReplicationSlot->data.twophase)
+		{
+			ctx->twophase = true;
+		}
+
 		/*
 		 * After the sanity checks in CreateDecodingContext, make sure the
 		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index eb283a8..aeec791 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -84,6 +84,7 @@ static SQLCmd *make_sqlcmd(void);
 %token K_SLOT
 %token K_RESERVE_WAL
 %token K_TEMPORARY
+%token K_TWOPHASE
 %token K_EXPORT_SNAPSHOT
 %token K_NOEXPORT_SNAPSHOT
 %token K_USE_SNAPSHOT
@@ -102,6 +103,7 @@ static SQLCmd *make_sqlcmd(void);
 %type <node>	plugin_opt_arg
 %type <str>		opt_slot var_name
 %type <boolval>	opt_temporary
+%type <boolval>	opt_twophase
 %type <list>	create_slot_opt_list
 %type <defelt>	create_slot_opt
 
@@ -242,15 +244,16 @@ create_replication_slot:
 					$$ = (Node *) cmd;
 				}
 			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin */
-			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list
+			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary opt_twophase K_LOGICAL IDENT create_slot_opt_list
 				{
 					CreateReplicationSlotCmd *cmd;
 					cmd = makeNode(CreateReplicationSlotCmd);
 					cmd->kind = REPLICATION_KIND_LOGICAL;
 					cmd->slotname = $2;
 					cmd->temporary = $3;
-					cmd->plugin = $5;
-					cmd->options = $6;
+					cmd->twophase = $4;
+					cmd->plugin = $6;
+					cmd->options = $7;
 					$$ = (Node *) cmd;
 				}
 			;
@@ -365,6 +368,11 @@ opt_temporary:
 			| /* EMPTY */					{ $$ = false; }
 			;
 
+opt_twophase:
+			K_TWOPHASE						{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
 opt_slot:
 			K_SLOT IDENT
 				{ $$ = $2; }
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index dcc3c3f..3032c28 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -103,6 +103,7 @@ RESERVE_WAL			{ return K_RESERVE_WAL; }
 LOGICAL				{ return K_LOGICAL; }
 SLOT				{ return K_SLOT; }
 TEMPORARY			{ return K_TEMPORARY; }
+TWOPHASE			{ return K_TWOPHASE; }
 EXPORT_SNAPSHOT		{ return K_EXPORT_SNAPSHOT; }
 NOEXPORT_SNAPSHOT	{ return K_NOEXPORT_SNAPSHOT; }
 USE_SNAPSHOT		{ return K_USE_SNAPSHOT; }
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..38c385b 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool twophase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.twophase    = twophase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index f5efdff..974f3af 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool twophase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, twophase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		twophase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									twophase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -801,6 +804,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8124454..9146e62 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -937,7 +937,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -951,7 +952,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->twophase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e1e4f3e..187418a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10502,10 +10502,10 @@
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..1a933e2 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		twophase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 5764293..c441af4 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -97,6 +97,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr  snapshot_was_exported_at;
 
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        twophase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -198,7 +203,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool twophase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
-- 
1.8.3.1

From 17ff5462c3c4137796e044e95e609cbe77df673c Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Fri, 26 Feb 2021 02:58:49 -0500
Subject: [PATCH v4] Avoid repeated decoding of prepared transactions.

Prepared transactions were decoded again after a restart on COMMIT PREPARED
when two-phase commits were enabled. This was done to avoid missing a prepared
transaction that is not part of initial snapshot. Now, this missing PREPARE is identified
by defining a new LSN called snapshot_was_exported_at_lsn and stored in the
slot and snapbuild structures. Prepared transactions that were prior this LSN
will be replayed on a COMMIT PREPARED.
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 doc/src/sgml/catalogs.sgml                         | 11 +++++++
 doc/src/sgml/logicaldecoding.sgml                  |  9 ++---
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/decode.c           |  2 ++
 src/backend/replication/logical/logical.c          |  3 +-
 src/backend/replication/logical/reorderbuffer.c    | 14 ++++----
 src/backend/replication/logical/snapbuild.c        | 23 ++++++++++++-
 src/backend/replication/slotfuncs.c                |  7 +++-
 src/include/catalog/pg_proc.dat                    |  6 ++--
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/slot.h                     |  6 ++++
 src/include/replication/snapbuild.h                |  4 ++-
 src/test/regress/expected/rules.out                |  3 +-
 15 files changed, 83 insertions(+), 73 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..c51870f 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index db29905..366a971 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -11479,6 +11479,17 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>snapshot_was_exported_at</structfield> <type>pg_lsn</type>
+      </para>
+      <para>
+       The address (<literal>LSN</literal>) at which the logical
+       slot found a consistent point at the time of slot creation.
+       <literal>NULL</literal> for physical slots.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>wal_status</structfield> <type>text</type>
       </para>
       <para>
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 6455664..18d592d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -191,9 +191,6 @@ postgres=# COMMIT PREPARED 'test_prepared1';
 postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
- 0/1689DC0 | 529 | BEGIN 529
- 0/1689DC0 | 529 | table public.data: INSERT: id[integer]:3 data[text]:'5'
- 0/1689FC0 | 529 | PREPARE TRANSACTION 'test_prepared1', txid 529
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
 (4 row)
 
@@ -822,10 +819,8 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter, can be used in this callback to
       check if the plugin has already received this <command>PREPARE</command>
-      in which case it can skip the remaining changes of the transaction.
-      This can only happen if the user restarts the decoding after receiving
-      the <command>PREPARE</command> for a transaction but before receiving
-      the <command>COMMIT PREPARED</command>, say because of some error.
+      in which case it can either error out or skip the remaining changes of 
+      the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..3f94398 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -893,6 +893,7 @@ CREATE VIEW pg_replication_slots AS
             L.catalog_xmin,
             L.restart_lsn,
             L.confirmed_flush_lsn,
+			L.snapshot_was_exported_at,
             L.wal_status,
             L.safe_wal_size
     FROM pg_get_replication_slots() AS L
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..7f83bbb 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -716,6 +716,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	if (two_phase)
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									SnapBuildExportAt(ctx->snapshot_builder),
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -854,6 +855,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..2ea82c6 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.snapshot_was_exported_at);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+	slot->data.snapshot_was_exported_at = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..8aefc7e 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2625,9 +2625,9 @@ ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
 
 /* Remember that we have skipped prepare */
 void
-ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
+ReorderBufferSkipPrepare(ReorderBuffer* rb, TransactionId xid)
 {
-	ReorderBufferTXN *txn;
+	ReorderBufferTXN* txn;
 
 	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
 
@@ -2672,6 +2672,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr snapshot_was_exported_at,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2698,12 +2699,11 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	/*
 	 * It is possible that this transaction is not decoded at prepare time
 	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < snapshot_was_exported_at) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..fe486c4 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,16 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported snapshot for initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot needs
+	 * to be sent later along with commit prepared and they must be before this
+	 * point.
+	 */
+	XLogRecPtr  snapshot_was_exported_at;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +279,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr snapshot_was_exported_at)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +308,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->snapshot_was_exported_at = snapshot_was_exported_at;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +369,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildExportAt(SnapBuild *builder)
+{
+	return builder->snapshot_was_exported_at;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..f5efdff 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -236,7 +236,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
-#define PG_GET_REPLICATION_SLOTS_COLS 13
+#define PG_GET_REPLICATION_SLOTS_COLS 14
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	TupleDesc	tupdesc;
 	Tuplestorestate *tupstore;
@@ -344,6 +344,11 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 		else
 			nulls[i++] = true;
 
+		if (slot_contents.data.snapshot_was_exported_at != InvalidXLogRecPtr)
+			values[i++] = LSNGetDatum(slot_contents.data.snapshot_was_exported_at);
+		else
+			nulls[i++] = true;
+
 		/*
 		 * If invalidated_at is valid and restart_lsn is invalid, we know for
 		 * certain that the slot has been invalidated.  Otherwise, test
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1604412..e1e4f3e 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10496,9 +10496,9 @@
   proname => 'pg_get_replication_slots', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size}',
+  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,pg_lsn,text,int8}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,snapshot_was_exported_at,wal_status,safe_wal_size}',
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..1dbb50e 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr snapshot_consistency_lsn,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..5764293 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,12 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported snapshot for initial copy.
+	 */
+	XLogRecPtr  snapshot_was_exported_at;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..f15ac66 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr snapshot_was_exported_at);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildExportAt(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 10a1f34..10647d4 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1476,9 +1476,10 @@ pg_replication_slots| SELECT l.slot_name,
     l.catalog_xmin,
     l.restart_lsn,
     l.confirmed_flush_lsn,
+    l.snapshot_was_exported_at,
     l.wal_status,
     l.safe_wal_size
-   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size)
+   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, snapshot_was_exported_at, wal_status, safe_wal_size)
      LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
 pg_roles| SELECT pg_authid.rolname,
     pg_authid.rolsuper,
-- 
1.8.3.1

From b4d4504b64452ba6cc8602f66acac8209317da0a Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Fri, 26 Feb 2021 02:58:49 -0500
Subject: [PATCH v5 1/2] Avoid repeated decoding of prepared transactions after
 the restart.

In commit a271a1b50e, we allowed decoding at prepare time and the prepare
was decoded again if there is a restart after decoding it. It was done
that way because we can't distinguish between the cases where we have not
decoded the prepare because it was prior to consistent snapshot or we have
decoded it earlier but restarted. To distinguish between these two cases,
we have introduced an initial_consisten_point at the slot level which is
an LSN at which we found a consistent point at the time of slot creation.
This is also the point where we have exported a snapshot for the initial
copy. So, prepare transaction prior to this point are sent along with
commit prepared.

Author: Ajin Cherian, based on idea by Andres Freund
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 doc/src/sgml/logicaldecoding.sgml                  |  9 ++---
 src/backend/replication/logical/decode.c           |  2 ++
 src/backend/replication/logical/logical.c          |  3 +-
 src/backend/replication/logical/reorderbuffer.c    | 10 +++---
 src/backend/replication/logical/snapbuild.c        | 24 +++++++++++++-
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/slot.h                     |  7 ++++
 src/include/replication/snapbuild.h                |  4 ++-
 10 files changed, 60 insertions(+), 66 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..c51870f 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 6455664..18d592d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -191,9 +191,6 @@ postgres=# COMMIT PREPARED 'test_prepared1';
 postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
- 0/1689DC0 | 529 | BEGIN 529
- 0/1689DC0 | 529 | table public.data: INSERT: id[integer]:3 data[text]:'5'
- 0/1689FC0 | 529 | PREPARE TRANSACTION 'test_prepared1', txid 529
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
 (4 row)
 
@@ -822,10 +819,8 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter, can be used in this callback to
       check if the plugin has already received this <command>PREPARE</command>
-      in which case it can skip the remaining changes of the transaction.
-      This can only happen if the user restarts the decoding after receiving
-      the <command>PREPARE</command> for a transaction but before receiving
-      the <command>COMMIT PREPARED</command>, say because of some error.
+      in which case it can either error out or skip the remaining changes of 
+      the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..423188d 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -716,6 +716,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	if (two_phase)
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									SnapBuildInitialConsistentPoint(ctx->snapshot_builder),
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -854,6 +855,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..3f6d723 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.initial_consistent_point);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+	slot->data.initial_consistent_point = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..91600ac 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2672,6 +2672,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr initial_consistent_point,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2698,12 +2699,11 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	/*
 	 * It is possible that this transaction is not decoded at prepare time
 	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < initial_consistent_point) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..6087467 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,17 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot
+	 * needs to be sent later along with commit prepared and they must be
+	 * before this point.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +280,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr initial_consistent_point)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +309,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->initial_consistent_point = initial_consistent_point;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +370,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildInitialConsistentPoint(SnapBuild *builder)
+{
+	return builder->initial_consistent_point;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..565a961 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr initial_consistent_point,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..5c3fde2 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,13 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..fbabce6 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr initial_consistent_point);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildInitialConsistentPoint(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
1.8.3.1

From 5a986ec983bea2740e20d95c8ee4db574237b68c Mon Sep 17 00:00:00 2001
From: Amit Kapila <akapila@postgresql.org>
Date: Sat, 27 Feb 2021 11:18:28 +0530
Subject: [PATCH v5 2/2] Add option to enable two-phase commits in
 pg_create_logical_replication_slot.

This commit changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 18 ++++--------
 doc/src/sgml/logicaldecoding.sgml                  | 19 ++++++------
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/logicalfuncs.c     |  8 +++++
 src/backend/replication/repl_gram.y                | 14 +++++++--
 src/backend/replication/repl_scanner.l             |  1 +
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 10 +++++--
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    |  8 ++---
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 18 files changed, 110 insertions(+), 84 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index c51870f..8d61107 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -139,7 +139,7 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -151,7 +151,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -167,7 +167,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -177,7 +177,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -188,14 +188,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -208,7 +208,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index 894e4f5..17ada0f 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -71,11 +71,11 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -87,26 +87,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..28c876d 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,12 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
+
+	/*
+	 * Disable two-phase here, it will be set in the core if it was
+	 * enabled whole creating the slot.
+	 */
+	ctx->twophase = false;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 18d592d..5839d96 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -169,17 +169,18 @@ $ pg_recvlogical -d postgres --slot=test --drop-slot
   <para>
   The following example shows SQL interface that can be used to decode prepared
   transactions. Before you use two-phase commit commands, you must set
-  <varname>max_prepared_transactions</varname> to at least 1. You must also set
-  the option 'two-phase-commit' to 1 while calling
-  <function>pg_logical_slot_get_changes</function>. Note that we will stream
-  the entire transaction after the commit if it is not already decoded.
+  <varname>max_prepared_transactions</varname> to at least 1. You must also have
+  set the two-phase parameter as 'true' while creating the slot using
+  <function>pg_create_logical_replication_slot</function>
+  Note that we will stream the entire transaction after the commit if it
+  is not already decoded.
   </para>
 <programlisting>
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +189,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
@@ -198,7 +199,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -207,7 +208,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..f6c5fc5 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1318,6 +1318,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index f7e0558..4a919d1 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -239,6 +239,14 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 									LogicalOutputPrepareWrite,
 									LogicalOutputWrite, NULL);
 
+		/* If twophase is set on the slot at create time, then
+		 * make sure the field in the context is also updated
+		 */
+		if (MyReplicationSlot->data.twophase)
+		{
+			ctx->twophase = true;
+		}
+
 		/*
 		 * After the sanity checks in CreateDecodingContext, make sure the
 		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index eb283a8..aeec791 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -84,6 +84,7 @@ static SQLCmd *make_sqlcmd(void);
 %token K_SLOT
 %token K_RESERVE_WAL
 %token K_TEMPORARY
+%token K_TWOPHASE
 %token K_EXPORT_SNAPSHOT
 %token K_NOEXPORT_SNAPSHOT
 %token K_USE_SNAPSHOT
@@ -102,6 +103,7 @@ static SQLCmd *make_sqlcmd(void);
 %type <node>	plugin_opt_arg
 %type <str>		opt_slot var_name
 %type <boolval>	opt_temporary
+%type <boolval>	opt_twophase
 %type <list>	create_slot_opt_list
 %type <defelt>	create_slot_opt
 
@@ -242,15 +244,16 @@ create_replication_slot:
 					$$ = (Node *) cmd;
 				}
 			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin */
-			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list
+			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary opt_twophase K_LOGICAL IDENT create_slot_opt_list
 				{
 					CreateReplicationSlotCmd *cmd;
 					cmd = makeNode(CreateReplicationSlotCmd);
 					cmd->kind = REPLICATION_KIND_LOGICAL;
 					cmd->slotname = $2;
 					cmd->temporary = $3;
-					cmd->plugin = $5;
-					cmd->options = $6;
+					cmd->twophase = $4;
+					cmd->plugin = $6;
+					cmd->options = $7;
 					$$ = (Node *) cmd;
 				}
 			;
@@ -365,6 +368,11 @@ opt_temporary:
 			| /* EMPTY */					{ $$ = false; }
 			;
 
+opt_twophase:
+			K_TWOPHASE						{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
 opt_slot:
 			K_SLOT IDENT
 				{ $$ = $2; }
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index dcc3c3f..3032c28 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -103,6 +103,7 @@ RESERVE_WAL			{ return K_RESERVE_WAL; }
 LOGICAL				{ return K_LOGICAL; }
 SLOT				{ return K_SLOT; }
 TEMPORARY			{ return K_TEMPORARY; }
+TWOPHASE			{ return K_TWOPHASE; }
 EXPORT_SNAPSHOT		{ return K_EXPORT_SNAPSHOT; }
 NOEXPORT_SNAPSHOT	{ return K_NOEXPORT_SNAPSHOT; }
 USE_SNAPSHOT		{ return K_USE_SNAPSHOT; }
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..38c385b 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool twophase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.twophase    = twophase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..a441fa4 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool twophase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, twophase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		twophase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									twophase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -796,6 +799,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8124454..9146e62 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -937,7 +937,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -951,7 +952,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->twophase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1487710..1d9e51a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10502,10 +10502,10 @@
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..1a933e2 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		twophase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 5c3fde2..f524544 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -98,6 +98,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	initial_consistent_point;
 
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        twophase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -199,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool twophase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
-- 
1.8.3.1

From aea5b0bc00cb4c282b3e659c492b825880c2e8e6 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Fri, 26 Feb 2021 02:58:49 -0500
Subject: [PATCH v6 1/2] Avoid repeated decoding of prepared transactions after
 the restart.

In commit a271a1b50e, we allowed decoding at prepare time and the prepare
was decoded again if there is a restart after decoding it. It was done
that way because we can't distinguish between the cases where we have not
decoded the prepare because it was prior to consistent snapshot or we have
decoded it earlier but restarted. To distinguish between these two cases,
we have introduced an initial_consisten_point at the slot level which is
an LSN at which we found a consistent point at the time of slot creation.
This is also the point where we have exported a snapshot for the initial
copy. So, prepare transaction prior to this point are sent along with
commit prepared.

This commit bumps SNAPBUILD_VERSION because of change in SnapBuild. It
will break existing slots which is fine in a major release.

Author: Ajin Cherian, based on idea by Andres Freund
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 doc/src/sgml/logicaldecoding.sgml                  |  9 ++---
 src/backend/replication/logical/decode.c           |  2 ++
 src/backend/replication/logical/logical.c          |  3 +-
 src/backend/replication/logical/reorderbuffer.c    | 10 +++---
 src/backend/replication/logical/snapbuild.c        | 26 +++++++++++++--
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/slot.h                     |  7 ++++
 src/include/replication/snapbuild.h                |  4 ++-
 10 files changed, 61 insertions(+), 67 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index f9f6bed..c51870f 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -159,14 +152,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -189,13 +178,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 6455664..18d592d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -191,9 +191,6 @@ postgres=# COMMIT PREPARED 'test_prepared1';
 postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
- 0/1689DC0 | 529 | BEGIN 529
- 0/1689DC0 | 529 | table public.data: INSERT: id[integer]:3 data[text]:'5'
- 0/1689FC0 | 529 | PREPARE TRANSACTION 'test_prepared1', txid 529
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
 (4 row)
 
@@ -822,10 +819,8 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter, can be used in this callback to
       check if the plugin has already received this <command>PREPARE</command>
-      in which case it can skip the remaining changes of the transaction.
-      This can only happen if the user restarts the decoding after receiving
-      the <command>PREPARE</command> for a transaction but before receiving
-      the <command>COMMIT PREPARED</command>, say because of some error.
+      in which case it can either error out or skip the remaining changes of 
+      the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..423188d 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -716,6 +716,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	if (two_phase)
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									SnapBuildInitialConsistentPoint(ctx->snapshot_builder),
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -854,6 +855,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..3f6d723 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.initial_consistent_point);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+	slot->data.initial_consistent_point = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..91600ac 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2672,6 +2672,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr initial_consistent_point,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2698,12 +2699,11 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	/*
 	 * It is possible that this transaction is not decoded at prepare time
 	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < initial_consistent_point) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..c42005e 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,17 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot
+	 * needs to be sent later along with commit prepared and they must be
+	 * before this point.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +280,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr initial_consistent_point)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +309,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->initial_consistent_point = initial_consistent_point;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +370,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildInitialConsistentPoint(SnapBuild *builder)
+{
+	return builder->initial_consistent_point;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
@@ -1422,7 +1444,7 @@ typedef struct SnapBuildOnDisk
 	offsetof(SnapBuildOnDisk, version)
 
 #define SNAPBUILD_MAGIC 0x51A1E001
-#define SNAPBUILD_VERSION 3
+#define SNAPBUILD_VERSION 4 
 
 /*
  * Store/Load a snapshot from disk, depending on the snapshot builder's state.
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..565a961 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr initial_consistent_point,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..5c3fde2 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,13 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..fbabce6 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr initial_consistent_point);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildInitialConsistentPoint(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
1.8.3.1

From a2b3e03e3321a81ed4bf10791cb66fa57c716fe0 Mon Sep 17 00:00:00 2001
From: Amit Kapila <akapila@postgresql.org>
Date: Sat, 27 Feb 2021 11:18:28 +0530
Subject: [PATCH v6 2/2] Add option to enable two-phase commits in
 pg_create_logical_replication_slot.

This commit changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 18 ++++--------
 doc/src/sgml/logicaldecoding.sgml                  | 19 ++++++------
 src/backend/catalog/system_views.sql               |  1 +
 src/backend/replication/logical/logicalfuncs.c     |  8 +++++
 src/backend/replication/repl_gram.y                | 14 +++++++--
 src/backend/replication/repl_scanner.l             |  1 +
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 10 +++++--
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    |  8 ++---
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 18 files changed, 110 insertions(+), 84 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index c51870f..8d61107 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -139,7 +139,7 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -151,7 +151,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -167,7 +167,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -177,7 +177,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -188,14 +188,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -208,7 +208,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index 894e4f5..17ada0f 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -71,11 +71,11 @@ WHERE locktype = 'relation'
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding. The
 -- call should return within a second.
 SET statement_timeout = '1s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -87,26 +87,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..28c876d 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,12 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
+
+	/*
+	 * Disable two-phase here, it will be set in the core if it was
+	 * enabled whole creating the slot.
+	 */
+	ctx->twophase = false;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 18d592d..5839d96 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -169,17 +169,18 @@ $ pg_recvlogical -d postgres --slot=test --drop-slot
   <para>
   The following example shows SQL interface that can be used to decode prepared
   transactions. Before you use two-phase commit commands, you must set
-  <varname>max_prepared_transactions</varname> to at least 1. You must also set
-  the option 'two-phase-commit' to 1 while calling
-  <function>pg_logical_slot_get_changes</function>. Note that we will stream
-  the entire transaction after the commit if it is not already decoded.
+  <varname>max_prepared_transactions</varname> to at least 1. You must also have
+  set the two-phase parameter as 'true' while creating the slot using
+  <function>pg_create_logical_replication_slot</function>
+  Note that we will stream the entire transaction after the commit if it
+  is not already decoded.
   </para>
 <programlisting>
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +189,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
@@ -198,7 +199,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -207,7 +208,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..f6c5fc5 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1318,6 +1318,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index f7e0558..4a919d1 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -239,6 +239,14 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 									LogicalOutputPrepareWrite,
 									LogicalOutputWrite, NULL);
 
+		/* If twophase is set on the slot at create time, then
+		 * make sure the field in the context is also updated
+		 */
+		if (MyReplicationSlot->data.twophase)
+		{
+			ctx->twophase = true;
+		}
+
 		/*
 		 * After the sanity checks in CreateDecodingContext, make sure the
 		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index eb283a8..aeec791 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -84,6 +84,7 @@ static SQLCmd *make_sqlcmd(void);
 %token K_SLOT
 %token K_RESERVE_WAL
 %token K_TEMPORARY
+%token K_TWOPHASE
 %token K_EXPORT_SNAPSHOT
 %token K_NOEXPORT_SNAPSHOT
 %token K_USE_SNAPSHOT
@@ -102,6 +103,7 @@ static SQLCmd *make_sqlcmd(void);
 %type <node>	plugin_opt_arg
 %type <str>		opt_slot var_name
 %type <boolval>	opt_temporary
+%type <boolval>	opt_twophase
 %type <list>	create_slot_opt_list
 %type <defelt>	create_slot_opt
 
@@ -242,15 +244,16 @@ create_replication_slot:
 					$$ = (Node *) cmd;
 				}
 			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin */
-			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list
+			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary opt_twophase K_LOGICAL IDENT create_slot_opt_list
 				{
 					CreateReplicationSlotCmd *cmd;
 					cmd = makeNode(CreateReplicationSlotCmd);
 					cmd->kind = REPLICATION_KIND_LOGICAL;
 					cmd->slotname = $2;
 					cmd->temporary = $3;
-					cmd->plugin = $5;
-					cmd->options = $6;
+					cmd->twophase = $4;
+					cmd->plugin = $6;
+					cmd->options = $7;
 					$$ = (Node *) cmd;
 				}
 			;
@@ -365,6 +368,11 @@ opt_temporary:
 			| /* EMPTY */					{ $$ = false; }
 			;
 
+opt_twophase:
+			K_TWOPHASE						{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
 opt_slot:
 			K_SLOT IDENT
 				{ $$ = $2; }
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index dcc3c3f..3032c28 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -103,6 +103,7 @@ RESERVE_WAL			{ return K_RESERVE_WAL; }
 LOGICAL				{ return K_LOGICAL; }
 SLOT				{ return K_SLOT; }
 TEMPORARY			{ return K_TEMPORARY; }
+TWOPHASE			{ return K_TWOPHASE; }
 EXPORT_SNAPSHOT		{ return K_EXPORT_SNAPSHOT; }
 NOEXPORT_SNAPSHOT	{ return K_NOEXPORT_SNAPSHOT; }
 USE_SNAPSHOT		{ return K_USE_SNAPSHOT; }
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..38c385b 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool twophase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.twophase    = twophase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..a441fa4 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool twophase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, twophase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		twophase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									twophase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -796,6 +799,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8124454..9146e62 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -937,7 +937,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -951,7 +952,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->twophase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1487710..1d9e51a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10502,10 +10502,10 @@
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..1a933e2 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		twophase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 5c3fde2..f524544 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -98,6 +98,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	initial_consistent_point;
 
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        twophase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -199,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool twophase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
-- 
1.8.3.1

From 12fde882b030338484190aa9bad6aa5619f96a2c Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Sun, 28 Feb 2021 04:47:09 -0500
Subject: [PATCH v7] Avoid repeated decoding of prepared transactions after a
 restart.

In commit a271a1b50e, we allowed decoding at prepare time and the prepare
was decoded again if there is a restart after decoding it. It was done
that way because we can't distinguish between the cases where we have not
decoded the prepare because it was prior to consistent snapshot or we have
decoded it earlier but restarted. To distinguish between these two cases,
we have introduced an initial_consisten_point at the slot level which is
an LSN at which we found a consistent point at the time of slot creation.
This is also the point where we have exported a snapshot for the initial
copy. So, prepare transaction prior to this point are sent along with
commit prepared.

This commit bumps SNAPBUILD_VERSION because of change in SnapBuild. It
will break existing slots which is fine in a major release.

Author: Ajin Cherian, based on idea by Andres Freund
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
---
 contrib/test_decoding/expected/twophase.out        | 38 +++++++---------------
 contrib/test_decoding/expected/twophase_stream.out | 28 ++--------------
 doc/src/sgml/logicaldecoding.sgml                  |  9 ++---
 src/backend/replication/logical/decode.c           |  2 ++
 src/backend/replication/logical/logical.c          |  3 +-
 src/backend/replication/logical/reorderbuffer.c    | 10 +++---
 src/backend/replication/logical/snapbuild.c        | 26 +++++++++++++--
 src/include/replication/reorderbuffer.h            |  1 +
 src/include/replication/slot.h                     |  7 ++++
 src/include/replication/snapbuild.h                |  4 ++-
 10 files changed, 61 insertions(+), 67 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index afa3566..8a1d06d 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#1';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                        data                        
-----------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:1
- table public.test_prepared1: INSERT: id[integer]:2
- PREPARE TRANSACTION 'test_prepared#1'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#1'
-(5 rows)
+(1 row)
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
@@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared#3';
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                  data                                   
--------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
- PREPARE TRANSACTION 'test_prepared#3'
+               data                
+-----------------------------------
  COMMIT PREPARED 'test_prepared#3'
-(4 rows)
+(1 row)
 
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
@@ -158,14 +151,10 @@ RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                                   data                                    
----------------------------------------------------------------------------
- BEGIN
- table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
- table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
- PREPARE TRANSACTION 'test_prepared_lock'
+                 data                 
+--------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
-(5 rows)
+(1 row)
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -188,13 +177,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
-                            data                            
-------------------------------------------------------------
- BEGIN
- table public.test_prepared_savepoint: INSERT: a[integer]:1
- PREPARE TRANSACTION 'test_prepared_savepoint'
+                   data                    
+-------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
-(4 rows)
+(1 row)
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index 3acc4acd3..d54e640 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
-                            data                             
--------------------------------------------------------------
- BEGIN
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
- table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
- PREPARE TRANSACTION 'test1'
+          data           
+-------------------------
  COMMIT PREPARED 'test1'
-(23 rows)
+(1 row)
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 6455664..18d592d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -191,9 +191,6 @@ postgres=# COMMIT PREPARED 'test_prepared1';
 postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
- 0/1689DC0 | 529 | BEGIN 529
- 0/1689DC0 | 529 | table public.data: INSERT: id[integer]:3 data[text]:'5'
- 0/1689FC0 | 529 | PREPARE TRANSACTION 'test_prepared1', txid 529
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
 (4 row)
 
@@ -822,10 +819,8 @@ typedef bool (*LogicalDecodeFilterPrepareCB) (struct LogicalDecodingContext *ctx
       <parameter>gid</parameter> field, which is part of the
       <parameter>txn</parameter> parameter, can be used in this callback to
       check if the plugin has already received this <command>PREPARE</command>
-      in which case it can skip the remaining changes of the transaction.
-      This can only happen if the user restarts the decoding after receiving
-      the <command>PREPARE</command> for a transaction but before receiving
-      the <command>COMMIT PREPARED</command>, say because of some error.
+      in which case it can either error out or skip the remaining changes of 
+      the transaction.
       <programlisting>
        typedef void (*LogicalDecodeBeginPrepareCB) (struct LogicalDecodingContext *ctx,
                                                     ReorderBufferTXN *txn);
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index afa1df0..423188d 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -716,6 +716,7 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	if (two_phase)
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									SnapBuildInitialConsistentPoint(ctx->snapshot_builder),
 									commit_time, origin_id, origin_lsn,
 									parsed->twophase_gid, true);
 	}
@@ -854,6 +855,7 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
 									abort_time, origin_id, origin_lsn,
+									InvalidXLogRecPtr,
 									parsed->twophase_gid, false);
 	}
 	else
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index baeb45f..3f6d723 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder = ReorderBufferAllocate();
 	ctx->snapshot_builder =
 		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
-								need_full_snapshot);
+								need_full_snapshot, slot->data.initial_consistent_point);
 
 	ctx->reorder->private_data = ctx;
 
@@ -590,6 +590,7 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 
 	SpinLockAcquire(&slot->mutex);
 	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+	slot->data.initial_consistent_point = ctx->reader->EndRecPtr;
 	SpinLockRelease(&slot->mutex);
 }
 
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index c3b9632..91600ac 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2672,6 +2672,7 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 void
 ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr initial_consistent_point,
 							TimestampTz commit_time, RepOriginId origin_id,
 							XLogRecPtr origin_lsn, char *gid, bool is_commit)
 {
@@ -2698,12 +2699,11 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 	/*
 	 * It is possible that this transaction is not decoded at prepare time
 	 * either because by that time we didn't have a consistent snapshot or it
-	 * was decoded earlier but we have restarted. We can't distinguish between
-	 * those two cases so we send the prepare in both the cases and let
-	 * downstream decide whether to process or skip it. We don't need to
-	 * decode the xact for aborts if it is not done already.
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
 	 */
-	if (!rbtxn_prepared(txn) && is_commit)
+	if ((txn->final_lsn < initial_consistent_point) && is_commit)
 	{
 		txn->txn_flags |= RBTXN_PREPARE;
 
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e117887..ed3acad 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -165,6 +165,17 @@ struct SnapBuild
 	XLogRecPtr	start_decoding_at;
 
 	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot
+	 * needs to be sent later along with commit prepared and they must be
+	 * before this point.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
+	/*
 	 * Don't start decoding WAL until the "xl_running_xacts" information
 	 * indicates there are no running xids with an xid smaller than this.
 	 */
@@ -269,7 +280,8 @@ SnapBuild *
 AllocateSnapshotBuilder(ReorderBuffer *reorder,
 						TransactionId xmin_horizon,
 						XLogRecPtr start_lsn,
-						bool need_full_snapshot)
+						bool need_full_snapshot,
+						XLogRecPtr initial_consistent_point)
 {
 	MemoryContext context;
 	MemoryContext oldcontext;
@@ -297,6 +309,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
 	builder->initial_xmin_horizon = xmin_horizon;
 	builder->start_decoding_at = start_lsn;
 	builder->building_full_snapshot = need_full_snapshot;
+	builder->initial_consistent_point = initial_consistent_point;
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -357,6 +370,15 @@ SnapBuildCurrentState(SnapBuild *builder)
 }
 
 /*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildInitialConsistentPoint(SnapBuild *builder)
+{
+	return builder->initial_consistent_point;
+}
+
+/*
  * Should the contents of transaction ending at 'ptr' be decoded?
  */
 bool
@@ -1422,7 +1444,7 @@ typedef struct SnapBuildOnDisk
 	offsetof(SnapBuildOnDisk, version)
 
 #define SNAPBUILD_MAGIC 0x51A1E001
-#define SNAPBUILD_VERSION 3
+#define SNAPBUILD_VERSION 4
 
 /*
  * Store/Load a snapshot from disk, depending on the snapshot builder's state.
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index bab31bf..565a961 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -643,6 +643,7 @@ void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
 void		ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 										XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+										XLogRecPtr initial_consistent_point,
 										TimestampTz commit_time,
 										RepOriginId origin_id, XLogRecPtr origin_lsn,
 										char *gid, bool is_commit);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 38a9a0b..5c3fde2 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -91,6 +91,13 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	confirmed_flush;
 
+	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h
index d9f187a..fbabce6 100644
--- a/src/include/replication/snapbuild.h
+++ b/src/include/replication/snapbuild.h
@@ -61,7 +61,8 @@ extern void CheckPointSnapBuild(void);
 
 extern SnapBuild *AllocateSnapshotBuilder(struct ReorderBuffer *cache,
 										  TransactionId xmin_horizon, XLogRecPtr start_lsn,
-										  bool need_full_snapshot);
+										  bool need_full_snapshot,
+										  XLogRecPtr initial_consistent_point);
 extern void FreeSnapshotBuilder(SnapBuild *cache);
 
 extern void SnapBuildSnapDecRefcount(Snapshot snap);
@@ -75,6 +76,7 @@ extern Snapshot SnapBuildGetOrBuildSnapshot(SnapBuild *builder,
 											TransactionId xid);
 
 extern bool SnapBuildXactNeedsSkip(SnapBuild *snapstate, XLogRecPtr ptr);
+extern XLogRecPtr SnapBuildInitialConsistentPoint(SnapBuild *builder);
 
 extern void SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn,
 							   TransactionId xid, int nsubxacts,
-- 
1.8.3.1

From 2e37345bf690b0a3d62b5e3f0b8b135159726f98 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Sun, 28 Feb 2021 05:07:19 -0500
Subject: [PATCH v7] Add option to enable two-phase commits in
 pg_create_logical_replication_slot.

This commit changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 13 +--------
 doc/src/sgml/catalogs.sgml                         |  9 ++++++
 doc/src/sgml/logicaldecoding.sgml                  | 19 ++++++------
 src/backend/catalog/system_views.sql               |  4 ++-
 src/backend/replication/logical/logical.c          |  6 ++++
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 14 ++++++---
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    | 14 ++++-----
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 src/test/regress/expected/rules.out                |  5 ++--
 18 files changed, 111 insertions(+), 88 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index 8a1d06d..e5e0f96 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -138,7 +138,7 @@ WHERE locktype = 'relation'
 
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding.
 SET statement_timeout = '180s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -150,7 +150,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -166,7 +166,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -176,7 +176,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -187,14 +187,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -207,7 +207,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index dacedfe..05f18e8 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -70,11 +70,11 @@ WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding.
 SET statement_timeout = '180s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -86,26 +86,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..3dfa503 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,7 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
+
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index db29905..2d61c351 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -11529,6 +11529,15 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
        is <literal>-1</literal>.
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>twophase</structfield> <type>bool</type>
+      </para>
+      <para>
+      True if two-phase commits are enabled on this slot.
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index 18d592d..5839d96 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -169,17 +169,18 @@ $ pg_recvlogical -d postgres --slot=test --drop-slot
   <para>
   The following example shows SQL interface that can be used to decode prepared
   transactions. Before you use two-phase commit commands, you must set
-  <varname>max_prepared_transactions</varname> to at least 1. You must also set
-  the option 'two-phase-commit' to 1 while calling
-  <function>pg_logical_slot_get_changes</function>. Note that we will stream
-  the entire transaction after the commit if it is not already decoded.
+  <varname>max_prepared_transactions</varname> to at least 1. You must also have
+  set the two-phase parameter as 'true' while creating the slot using
+  <function>pg_create_logical_replication_slot</function>
+  Note that we will stream the entire transaction after the commit if it
+  is not already decoded.
   </para>
 <programlisting>
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +189,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
@@ -198,7 +199,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -207,7 +208,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..c3c7583 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -894,7 +894,8 @@ CREATE VIEW pg_replication_slots AS
             L.restart_lsn,
             L.confirmed_flush_lsn,
             L.wal_status,
-            L.safe_wal_size
+            L.safe_wal_size,
+			L.twophase
     FROM pg_get_replication_slots() AS L
             LEFT JOIN pg_database D ON (L.datoid = D.oid);
 
@@ -1318,6 +1319,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 3f6d723..28d18e8 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -533,6 +533,12 @@ CreateDecodingContext(XLogRecPtr start_lsn,
 
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
+	/*
+	 * If twophase is set on the slot at create time, then
+	 * make sure the field in the context is also updated.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.twophase;
+
 	ereport(LOG,
 			(errmsg("starting logical decoding for slot \"%s\"",
 					NameStr(slot->data.name)),
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..38c385b 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool twophase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.twophase    = twophase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..5b2864a 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool twophase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, twophase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		twophase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									twophase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -236,7 +239,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
-#define PG_GET_REPLICATION_SLOTS_COLS 13
+#define PG_GET_REPLICATION_SLOTS_COLS 14
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	TupleDesc	tupdesc;
 	Tuplestorestate *tupstore;
@@ -432,6 +435,8 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 			values[i++] = Int64GetDatum(failLSN - currlsn);
 		}
 
+		values[i++] = BoolGetDatum(slot_contents.data.twophase);
+
 		Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
@@ -796,6 +801,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 8124454..9146e62 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -937,7 +937,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -951,7 +952,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->twophase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1487710..b83abda 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10496,16 +10496,16 @@
   proname => 'pg_get_replication_slots', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size}',
+  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8,bool}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size,twophase}',
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..1a933e2 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		twophase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 5c3fde2..f524544 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -98,6 +98,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	initial_consistent_point;
 
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        twophase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -199,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool twophase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 10a1f34..9a054d1 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1477,8 +1477,9 @@ pg_replication_slots| SELECT l.slot_name,
     l.restart_lsn,
     l.confirmed_flush_lsn,
     l.wal_status,
-    l.safe_wal_size
-   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size)
+    l.safe_wal_size,
+    l.twophase
+   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size, twophase)
      LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
 pg_roles| SELECT pg_authid.rolname,
     pg_authid.rolsuper,
-- 
1.8.3.1

From 7b4b8c9dbc49dd79defbb55e4b9dae409cb5c368 Mon Sep 17 00:00:00 2001
From: Ajin Cherian <ajinc@fast.au.fujitsu.com>
Date: Mon, 1 Mar 2021 19:42:56 -0500
Subject: [PATCH v8] Add option to enable two-phase commits in
 pg_create_logical_replication_slot.

This commit changes the way two-phase commits are enabled in test_decoding plugin.
Two-phase commits can now only be enabled while creating the slot using
pg_create_logical_replication_slot() and cannot be set using pg_logical_slot_get_changes().
For this the API pg_create_logical_replication_slot() is modified to take one more
optional boolean parameter 'twophase', which when set to TRUE enables two-phase commits.
The parameter defaults to FALSE.
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 12 --------
 doc/src/sgml/catalogs.sgml                         |  9 ++++++
 doc/src/sgml/logicaldecoding.sgml                  | 19 ++++++------
 src/backend/catalog/system_views.sql               |  4 ++-
 src/backend/replication/logical/logical.c          | 12 ++++++++
 src/backend/replication/slot.c                     |  3 +-
 src/backend/replication/slotfuncs.c                | 14 ++++++---
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    | 14 ++++-----
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 src/test/regress/expected/rules.out                |  5 ++--
 18 files changed, 116 insertions(+), 88 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index 8a1d06d..e5e0f96 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -138,7 +138,7 @@ WHERE locktype = 'relation'
 
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding.
 SET statement_timeout = '180s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -150,7 +150,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -166,7 +166,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -176,7 +176,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -187,14 +187,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -207,7 +207,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index dacedfe..05f18e8 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -70,11 +70,11 @@ WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding.
 SET statement_timeout = '180s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -86,26 +86,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..ae5f397 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index db29905..a68f3b8 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -11529,6 +11529,15 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
        is <literal>-1</literal>.
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>two_phase</structfield> <type>bool</type>
+      </para>
+      <para>
+      True if two-phase commits are enabled on this slot.
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index f1f13d8..80eb96d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -169,17 +169,18 @@ $ pg_recvlogical -d postgres --slot=test --drop-slot
   <para>
   The following example shows SQL interface that can be used to decode prepared
   transactions. Before you use two-phase commit commands, you must set
-  <varname>max_prepared_transactions</varname> to at least 1. You must also set
-  the option 'two-phase-commit' to 1 while calling
-  <function>pg_logical_slot_get_changes</function>. Note that we will stream
-  the entire transaction after the commit if it is not already decoded.
+  <varname>max_prepared_transactions</varname> to at least 1. You must also have
+  set the two-phase parameter as 'true' while creating the slot using
+  <function>pg_create_logical_replication_slot</function>
+  Note that we will stream the entire transaction after the commit if it
+  is not already decoded.
   </para>
 <programlisting>
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +189,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
@@ -198,7 +199,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -207,7 +208,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..fc94a73 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -894,7 +894,8 @@ CREATE VIEW pg_replication_slots AS
             L.restart_lsn,
             L.confirmed_flush_lsn,
             L.wal_status,
-            L.safe_wal_size
+            L.safe_wal_size,
+            L.two_phase
     FROM pg_get_replication_slots() AS L
             LEFT JOIN pg_database D ON (L.datoid = D.oid);
 
@@ -1318,6 +1319,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 3f6d723..c2aa46d 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -431,6 +431,12 @@ CreateInitDecodingContext(const char *plugin,
 		startup_cb_wrapper(ctx, &ctx->options, true);
 	MemoryContextSwitchTo(old_context);
 
+	/*
+	 * If two_phase is set on the slot at create time, then
+	 * make sure the field in the context is also updated.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.two_phase;
+
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
 	return ctx;
@@ -533,6 +539,12 @@ CreateDecodingContext(XLogRecPtr start_lsn,
 
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
+	/*
+	 * If two_phase is set on the slot at create time, then
+	 * make sure the field in the context is also updated.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.two_phase;
+
 	ereport(LOG,
 			(errmsg("starting logical decoding for slot \"%s\"",
 					NameStr(slot->data.name)),
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..acd14b2 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -219,7 +219,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool two_phase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +277,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.two_phase    = two_phase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..9817b44 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool two_phase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		two_phase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									two_phase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -236,7 +239,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
-#define PG_GET_REPLICATION_SLOTS_COLS 13
+#define PG_GET_REPLICATION_SLOTS_COLS 14
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	TupleDesc	tupdesc;
 	Tuplestorestate *tupstore;
@@ -432,6 +435,8 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 			values[i++] = Int64GetDatum(failLSN - currlsn);
 		}
 
+		values[i++] = BoolGetDatum(slot_contents.data.two_phase);
+
 		Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
@@ -796,6 +801,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index eb3f18e..23baa44 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -938,7 +938,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -952,7 +953,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->two_phase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1487710..3d3974f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10496,16 +10496,16 @@
   proname => 'pg_get_replication_slots', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size}',
+  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8,bool}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size,two_phase}',
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..ebc43a0 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		two_phase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 5c3fde2..320b2e5 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -98,6 +98,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	initial_consistent_point;
 
+	/*
+	 * Is the slot two-phase enabled?
+	 */
+	bool        two_phase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -199,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool two_phase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 10a1f34..b1c9b7b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1477,8 +1477,9 @@ pg_replication_slots| SELECT l.slot_name,
     l.restart_lsn,
     l.confirmed_flush_lsn,
     l.wal_status,
-    l.safe_wal_size
-   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size)
+    l.safe_wal_size,
+    l.two_phase
+   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size, two_phase)
      LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
 pg_roles| SELECT pg_authid.rolname,
     pg_authid.rolsuper,
-- 
1.8.3.1

From b95a9bfb6c689556bbe9a1d0c2b201f82a06b91f Mon Sep 17 00:00:00 2001
From: Amit Kapila <akapila@postgresql.org>
Date: Tue, 2 Mar 2021 09:07:07 +0530
Subject: [PATCH v9] Add option to enable two_phase commits via
 pg_create_logical_replication_slot.

Commit 0aa8a01d04 extends the output plugin API to allow decoding of
prepared xacts and allowed the user to enable/disable the two-phase option
via pg_logical_slot_get_changes(). This can lead to a problem such that
the first time when it gets changes via pg_logical_slot_get_changes()
without 2PC enabled it will not get the prepared even though prepare is
after consistent snapshot. Now next time during getting changes, if the
2PC option is enabled it can skip prepare because by that time start
decoding point has been moved. So the user will only get commit prepared.

Allow to enable/disable this option at the create slot time and default
will be false. It will break the existing slots which is fine in a major
release.

Author: Ajin Cherian
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
---
 contrib/test_decoding/expected/twophase.out        | 34 +++++++++++-----------
 .../test_decoding/expected/twophase_snapshot.out   |  6 ++--
 contrib/test_decoding/expected/twophase_stream.out | 10 +++----
 contrib/test_decoding/specs/twophase_snapshot.spec |  4 +--
 contrib/test_decoding/sql/twophase.sql             | 34 +++++++++++-----------
 contrib/test_decoding/sql/twophase_stream.sql      | 10 +++----
 contrib/test_decoding/test_decoding.c              | 12 --------
 doc/src/sgml/catalogs.sgml                         | 10 +++++++
 doc/src/sgml/func.sgml                             | 10 ++++---
 doc/src/sgml/logicaldecoding.sgml                  | 19 ++++++------
 src/backend/catalog/system_views.sql               |  4 ++-
 src/backend/replication/logical/logical.c          | 12 ++++++++
 src/backend/replication/slot.c                     | 10 ++++++-
 src/backend/replication/slotfuncs.c                | 14 ++++++---
 src/backend/replication/walsender.c                |  6 ++--
 src/include/catalog/pg_proc.dat                    | 14 ++++-----
 src/include/nodes/replnodes.h                      |  1 +
 src/include/replication/slot.h                     |  7 ++++-
 src/test/regress/expected/rules.out                |  5 ++--
 19 files changed, 130 insertions(+), 92 deletions(-)

diff --git a/contrib/test_decoding/expected/twophase.out b/contrib/test_decoding/expected/twophase.out
index 8a1d06d..e5e0f96 100644
--- a/contrib/test_decoding/expected/twophase.out
+++ b/contrib/test_decoding/expected/twophase.out
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -15,14 +15,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -32,7 +32,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (4 rows)
 
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#1'
@@ -42,7 +42,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -51,7 +51,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                 data                 
 -------------------------------------
  ROLLBACK PREPARED 'test_prepared#2'
@@ -74,7 +74,7 @@ WHERE locktype = 'relation'
 (2 rows)
 
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                   data                                   
 -------------------------------------------------------------------------
  BEGIN
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                         data                        
 ----------------------------------------------------
  BEGIN
@@ -98,7 +98,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 (3 rows)
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                data                
 -----------------------------------
  COMMIT PREPARED 'test_prepared#3'
@@ -107,7 +107,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                
 --------------------------------------------------------------------
  BEGIN
@@ -138,7 +138,7 @@ WHERE locktype = 'relation'
 
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding.
 SET statement_timeout = '180s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                    data                                    
 ---------------------------------------------------------------------------
  BEGIN
@@ -150,7 +150,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                  data                 
 --------------------------------------
  COMMIT PREPARED 'test_prepared_lock'
@@ -166,7 +166,7 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                             data                            
 ------------------------------------------------------------
  BEGIN
@@ -176,7 +176,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                    data                    
 -------------------------------------------
  COMMIT PREPARED 'test_prepared_savepoint'
@@ -187,14 +187,14 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
 
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
                                 data                                 
 ---------------------------------------------------------------------
  BEGIN
@@ -207,7 +207,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
  data 
 ------
 (0 rows)
diff --git a/contrib/test_decoding/expected/twophase_snapshot.out b/contrib/test_decoding/expected/twophase_snapshot.out
index 14d9387..0e8e1f5 100644
--- a/contrib/test_decoding/expected/twophase_snapshot.out
+++ b/contrib/test_decoding/expected/twophase_snapshot.out
@@ -6,7 +6,7 @@ step s2txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
 
 f              
-step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true); <waiting ...>
 step s3b: BEGIN;
 step s3txid: SELECT pg_current_xact_id() IS NULL;
 ?column?       
@@ -22,14 +22,14 @@ step s1init: <... completed>
 
 init           
 step s1insert: INSERT INTO do_write DEFAULT VALUES;
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
 table public.do_write: INSERT: id[integer]:2
 COMMIT         
 step s2cp: COMMIT PREPARED 'test1';
-step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');
+step s1start: SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');
 data           
 
 BEGIN          
diff --git a/contrib/test_decoding/expected/twophase_stream.out b/contrib/test_decoding/expected/twophase_stream.out
index d54e640..b08bb0e 100644
--- a/contrib/test_decoding/expected/twophase_stream.out
+++ b/contrib/test_decoding/expected/twophase_stream.out
@@ -1,6 +1,6 @@
 -- Test streaming of two-phase commits
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
  ?column? 
 ----------
  init
@@ -28,7 +28,7 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -59,7 +59,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
           data           
 -------------------------
  COMMIT PREPARED 'test1'
@@ -81,7 +81,7 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                            data                           
 ----------------------------------------------------------
  streaming message: transactional: 1 prefix: test, sz: 50
@@ -89,7 +89,7 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
                             data                             
 -------------------------------------------------------------
  BEGIN
diff --git a/contrib/test_decoding/specs/twophase_snapshot.spec b/contrib/test_decoding/specs/twophase_snapshot.spec
index 3e70040..e8d9567 100644
--- a/contrib/test_decoding/specs/twophase_snapshot.spec
+++ b/contrib/test_decoding/specs/twophase_snapshot.spec
@@ -15,8 +15,8 @@ teardown
 session "s1"
 setup { SET synchronous_commit=on; }
 
-step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
-step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1', 'two-phase-commit', '1');}
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding', false, true);}
+step "s1start" {SELECT data  FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false', 'skip-empty-xacts', '1');}
 step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
 
 session "s2"
diff --git a/contrib/test_decoding/sql/twophase.sql b/contrib/test_decoding/sql/twophase.sql
index dacedfe..05f18e8 100644
--- a/contrib/test_decoding/sql/twophase.sql
+++ b/contrib/test_decoding/sql/twophase.sql
@@ -1,7 +1,7 @@
 -- Test prepared transactions. When two-phase-commit is enabled, transactions are
 -- decoded at PREPARE time rather than at COMMIT PREPARED time.
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE test_prepared1(id integer primary key);
 CREATE TABLE test_prepared2(id integer primary key);
@@ -12,20 +12,20 @@ BEGIN;
 INSERT INTO test_prepared1 VALUES (1);
 INSERT INTO test_prepared1 VALUES (2);
 -- should show nothing because the xact has not been prepared yet.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 PREPARE TRANSACTION 'test_prepared#1';
 -- should show both the above inserts and the PREPARE TRANSACTION.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared#1';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that rollback of a prepared xact is decoded.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (3);
 PREPARE TRANSACTION 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 ROLLBACK PREPARED 'test_prepared#2';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test prepare of a xact containing ddl. Leaving xact uncommitted for next test.
 BEGIN;
@@ -38,7 +38,7 @@ FROM pg_locks
 WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The insert should show the newly altered column but not the DDL.
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that we decode correctly while an uncommitted prepared xact
 -- with ddl exists.
@@ -47,14 +47,14 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
 -- the ALTER will stop us inserting into the other one.
 --
 INSERT INTO test_prepared2 VALUES (5);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 COMMIT PREPARED 'test_prepared#3';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 -- make sure stuff still works
 INSERT INTO test_prepared1 VALUES (6);
 INSERT INTO test_prepared2 VALUES (7);
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Check 'CLUSTER' (as operation that hold exclusive lock) doesn't block
 -- logical decoding.
@@ -70,11 +70,11 @@ WHERE locktype = 'relation'
   AND relation = 'test_prepared1'::regclass;
 -- The above CLUSTER command shouldn't cause a timeout on 2pc decoding.
 SET statement_timeout = '180s';
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 RESET statement_timeout;
 COMMIT PREPARED 'test_prepared_lock';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test savepoints and sub-xacts. Creating savepoints will create
 -- sub-xacts implicitly.
@@ -86,26 +86,26 @@ INSERT INTO test_prepared_savepoint VALUES (2);
 ROLLBACK TO SAVEPOINT test_savepoint;
 PREPARE TRANSACTION 'test_prepared_savepoint';
 -- should show only 1, not 2
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_savepoint';
 -- consume the commit
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
 BEGIN;
 INSERT INTO test_prepared1 VALUES (20);
 PREPARE TRANSACTION 'test_prepared_nodecode';
 -- should show nothing
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 COMMIT PREPARED 'test_prepared_nodecode';
 -- should be decoded now
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 -- Test 8:
 -- cleanup and make sure results are also empty
 DROP TABLE test_prepared1;
 DROP TABLE test_prepared2;
 -- show results. There should be nothing to show
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/sql/twophase_stream.sql b/contrib/test_decoding/sql/twophase_stream.sql
index e9dd44f..646076d 100644
--- a/contrib/test_decoding/sql/twophase_stream.sql
+++ b/contrib/test_decoding/sql/twophase_stream.sql
@@ -1,7 +1,7 @@
 -- Test streaming of two-phase commits
 
 SET synchronous_commit = on;
-SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
 
 CREATE TABLE stream_test(data text);
 
@@ -18,11 +18,11 @@ ROLLBACK TO s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1';
 -- should show the inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1';
 --should show the COMMIT PREPARED and the other changes in the transaction
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 -- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
 -- filtered gid. gids with '_nodecode' will not be decoded at prepare time.
@@ -35,11 +35,11 @@ ROLLBACK to s1;
 INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM generate_series(1, 20) g(i);
 PREPARE TRANSACTION 'test1_nodecode';
 -- should NOT show inserts after a ROLLBACK
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 COMMIT PREPARED 'test1_nodecode';
 -- should show the inserts but not show a COMMIT PREPARED but a COMMIT
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
 
 DROP TABLE stream_test;
 SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index 929255e..ae5f397 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -164,7 +164,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	ListCell   *option;
 	TestDecodingData *data;
 	bool		enable_streaming = false;
-	bool		enable_twophase = false;
 
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
@@ -265,16 +264,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
-		else if (strcmp(elem->defname, "two-phase-commit") == 0)
-		{
-			if (elem->arg == NULL)
-				continue;
-			else if (!parse_bool(strVal(elem->arg), &enable_twophase))
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
-								strVal(elem->arg), elem->defname)));
-		}
 		else
 		{
 			ereport(ERROR,
@@ -286,7 +275,6 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	}
 
 	ctx->streaming &= enable_streaming;
-	ctx->twophase &= enable_twophase;
 }
 
 /* cleanup this plugin's resources */
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index db29905..b1de6d0 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -11529,6 +11529,16 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
        is <literal>-1</literal>.
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>two_phase</structfield> <type>bool</type>
+      </para>
+      <para>
+       True if the slot is enabled for decoding prepared transactions.  Always
+       false for physical slots.
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 08f0832..ad676dd 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -25556,7 +25556,7 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
         <indexterm>
          <primary>pg_create_logical_replication_slot</primary>
         </indexterm>
-        <function>pg_create_logical_replication_slot</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>plugin</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type> </optional> )
+        <function>pg_create_logical_replication_slot</function> ( <parameter>slot_name</parameter> <type>name</type>, <parameter>plugin</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type>, <parameter>two_phase</parameter> <type>boolean</type> </optional> )
         <returnvalue>record</returnvalue>
         ( <parameter>slot_name</parameter> <type>name</type>,
         <parameter>lsn</parameter> <type>pg_lsn</type> )
@@ -25568,9 +25568,11 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
         parameter, <parameter>temporary</parameter>, when set to true, specifies that
         the slot should not be permanently stored to disk and is only meant
         for use by the current session. Temporary slots are also
-        released upon any error. A call to this function has the same
-        effect as the replication protocol command
-        <literal>CREATE_REPLICATION_SLOT ... LOGICAL</literal>.
+        released upon any error. The optional fourth parameter,
+        <parameter>two_phase</parameter>, when set to true, specifies
+        that the decoding of prepared transactions is enabled for this
+        slot. A call to this function has the same effect as the replication
+        protocol command <literal>CREATE_REPLICATION_SLOT ... LOGICAL</literal>.
        </para></entry>
       </row>
 
diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml
index f1f13d8..80eb96d 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -55,7 +55,7 @@
 
 <programlisting>
 postgres=# -- Create a slot named 'regression_slot' using the output plugin 'test_decoding'
-postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+postgres=# SELECT * FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding', false, true);
     slot_name    |    lsn
 -----------------+-----------
  regression_slot | 0/16B1970
@@ -169,17 +169,18 @@ $ pg_recvlogical -d postgres --slot=test --drop-slot
   <para>
   The following example shows SQL interface that can be used to decode prepared
   transactions. Before you use two-phase commit commands, you must set
-  <varname>max_prepared_transactions</varname> to at least 1. You must also set
-  the option 'two-phase-commit' to 1 while calling
-  <function>pg_logical_slot_get_changes</function>. Note that we will stream
-  the entire transaction after the commit if it is not already decoded.
+  <varname>max_prepared_transactions</varname> to at least 1. You must also have
+  set the two-phase parameter as 'true' while creating the slot using
+  <function>pg_create_logical_replication_slot</function>
+  Note that we will stream the entire transaction after the commit if it
+  is not already decoded.
   </para>
 <programlisting>
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('5');
 postgres=*# PREPARE TRANSACTION 'test_prepared1';
 
-postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/1689DC0 | 529 | BEGIN 529
@@ -188,7 +189,7 @@ postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# COMMIT PREPARED 'test_prepared1';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                    data                    
 -----------+-----+--------------------------------------------
  0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
@@ -198,7 +199,7 @@ postgres=#-- you can also rollback a prepared transaction
 postgres=# BEGIN;
 postgres=*# INSERT INTO data(data) VALUES('6');
 postgres=*# PREPARE TRANSACTION 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                          data                           
 -----------+-----+---------------------------------------------------------
  0/168A180 | 530 | BEGIN 530
@@ -207,7 +208,7 @@ postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NU
 (3 rows)
 
 postgres=# ROLLBACK PREPARED 'test_prepared2';
-postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1');
+postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
     lsn    | xid |                     data                     
 -----------+-----+----------------------------------------------
  0/168A4B8 | 530 | ROLLBACK PREPARED 'test_prepared2', txid 530
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fa58afd..fc94a73 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -894,7 +894,8 @@ CREATE VIEW pg_replication_slots AS
             L.restart_lsn,
             L.confirmed_flush_lsn,
             L.wal_status,
-            L.safe_wal_size
+            L.safe_wal_size,
+            L.two_phase
     FROM pg_get_replication_slots() AS L
             LEFT JOIN pg_database D ON (L.datoid = D.oid);
 
@@ -1318,6 +1319,7 @@ AS 'pg_create_physical_replication_slot';
 CREATE OR REPLACE FUNCTION pg_create_logical_replication_slot(
     IN slot_name name, IN plugin name,
     IN temporary boolean DEFAULT false,
+    IN twophase boolean DEFAULT false,
     OUT slot_name name, OUT lsn pg_lsn)
 RETURNS RECORD
 LANGUAGE INTERNAL
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 3f6d723..37b75de 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -431,6 +431,12 @@ CreateInitDecodingContext(const char *plugin,
 		startup_cb_wrapper(ctx, &ctx->options, true);
 	MemoryContextSwitchTo(old_context);
 
+	/*
+	 * We allow decoding of prepared transactions iff the two_phase option is
+	 * enabled at the time of slot creation.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.two_phase;
+
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
 	return ctx;
@@ -531,6 +537,12 @@ CreateDecodingContext(XLogRecPtr start_lsn,
 		startup_cb_wrapper(ctx, &ctx->options, false);
 	MemoryContextSwitchTo(old_context);
 
+	/*
+	 * We allow decoding of prepared transactions iff the two_phase option is
+	 * enabled at the time of slot creation.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.two_phase;
+
 	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
 
 	ereport(LOG,
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb4af2e..75a087c 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -216,10 +216,17 @@ ReplicationSlotValidateName(const char *name, int elevel)
  * name: Name of the slot
  * db_specific: logical decoding is db specific; if the slot is going to
  *	   be used for that pass true, otherwise false.
+ * two_phase: Allows decoding of prepared transactions. We allow this option
+ *     to be enabled only at the slot creation time. If we allow this option
+ *     to be changed during decoding then it is quite possible that we skip
+ *     prepare first time because this option was not enabled. Now next time
+ *     during getting changes, if the two_phase  option is enabled it can skip
+ *     prepare because by that time start decoding point has been moved. So the
+ *     user will only get commit prepared.
  */
 void
 ReplicationSlotCreate(const char *name, bool db_specific,
-					  ReplicationSlotPersistency persistency)
+					  ReplicationSlotPersistency persistency, bool two_phase)
 {
 	ReplicationSlot *slot = NULL;
 	int			i;
@@ -277,6 +284,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;
+	slot->data.two_phase = two_phase;
 
 	/* and then data only present in shared memory */
 	slot->just_dirtied = false;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index d24bb5b..9817b44 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
 
 	/* acquire replication slot, this will check for conflicting names */
 	ReplicationSlotCreate(name, false,
-						  temporary ? RS_TEMPORARY : RS_PERSISTENT);
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
 
 	if (immediately_reserve)
 	{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
  */
 static void
 create_logical_replication_slot(char *name, char *plugin,
-								bool temporary, XLogRecPtr restart_lsn,
+								bool temporary, bool two_phase,
+								XLogRecPtr restart_lsn,
 								bool find_startpoint)
 {
 	LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	 * error as well.
 	 */
 	ReplicationSlotCreate(name, true,
-						  temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase);
 
 	/*
 	 * Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	Name		name = PG_GETARG_NAME(0);
 	Name		plugin = PG_GETARG_NAME(1);
 	bool		temporary = PG_GETARG_BOOL(2);
+	bool		two_phase = PG_GETARG_BOOL(3);
 	Datum		result;
 	TupleDesc	tupdesc;
 	HeapTuple	tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	create_logical_replication_slot(NameStr(*name),
 									NameStr(*plugin),
 									temporary,
+									two_phase,
 									InvalidXLogRecPtr,
 									true);
 
@@ -236,7 +239,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
-#define PG_GET_REPLICATION_SLOTS_COLS 13
+#define PG_GET_REPLICATION_SLOTS_COLS 14
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	TupleDesc	tupdesc;
 	Tuplestorestate *tupstore;
@@ -432,6 +435,8 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 			values[i++] = Int64GetDatum(failLSN - currlsn);
 		}
 
+		values[i++] = BoolGetDatum(slot_contents.data.two_phase);
+
 		Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
@@ -796,6 +801,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		create_logical_replication_slot(NameStr(*dst_name),
 										plugin,
 										temporary,
+										false,
 										src_restart_lsn,
 										false);
 	}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index eb3f18e..23baa44 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -938,7 +938,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
 	{
 		ReplicationSlotCreate(cmd->slotname, false,
-							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
 	}
 	else
 	{
@@ -952,7 +953,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		 * they get dropped on error as well.
 		 */
 		ReplicationSlotCreate(cmd->slotname, true,
-							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  cmd->two_phase);
 	}
 
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 1487710..3d3974f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10496,16 +10496,16 @@
   proname => 'pg_get_replication_slots', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size}',
+  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8,bool}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,safe_wal_size,two_phase}',
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
-  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
-  proallargtypes => '{name,name,bool,name,pg_lsn}',
-  proargmodes => '{i,i,i,o,o}',
-  proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool bool',
+  proallargtypes => '{name,name,bool,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{slot_name,plugin,temporary,twophase,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
 { oid => '4222',
   descr => 'copy a logical replication slot, changing temporality and plugin',
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index faa3a25..ebc43a0 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -56,6 +56,7 @@ typedef struct CreateReplicationSlotCmd
 	ReplicationKind kind;
 	char	   *plugin;
 	bool		temporary;
+	bool		two_phase;
 	List	   *options;
 } CreateReplicationSlotCmd;
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 5c3fde2..1ad5e6c 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -98,6 +98,11 @@ typedef struct ReplicationSlotPersistentData
 	 */
 	XLogRecPtr	initial_consistent_point;
 
+	/*
+	 * Allow decoding of prepared transactions?
+	 */
+	bool		two_phase;
+
 	/* plugin name */
 	NameData	plugin;
 } ReplicationSlotPersistentData;
@@ -199,7 +204,7 @@ extern void ReplicationSlotsShmemInit(void);
 
 /* management of individual slots */
 extern void ReplicationSlotCreate(const char *name, bool db_specific,
-								  ReplicationSlotPersistency p);
+								  ReplicationSlotPersistency p, bool two_phase);
 extern void ReplicationSlotPersist(void);
 extern void ReplicationSlotDrop(const char *name, bool nowait);
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 10a1f34..b1c9b7b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1477,8 +1477,9 @@ pg_replication_slots| SELECT l.slot_name,
     l.restart_lsn,
     l.confirmed_flush_lsn,
     l.wal_status,
-    l.safe_wal_size
-   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size)
+    l.safe_wal_size,
+    l.two_phase
+   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn, wal_status, safe_wal_size, two_phase)
      LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
 pg_roles| SELECT pg_authid.rolname,
     pg_authid.rolsuper,
-- 
1.8.3.1