Patch for migration of the pg_commit_ts directory

From 64dbcbbb3b02eecfe9cc71deaaabe2140b199ab8 Mon Sep 17 00:00:00 2001
From: Sergey Levin <ls7777@yandex.ru>
Date: Sat, 4 Oct 2025 20:22:46 +0500
Subject: [PATCH] Migration of the pg_commit_ts directory

---
 src/bin/pg_upgrade/check.c                    |  16 +-
 src/bin/pg_upgrade/controldata.c              |  26 +++-
 src/bin/pg_upgrade/info.c                     |  29 ++++
 src/bin/pg_upgrade/pg_upgrade.c               |  21 ++-
 src/bin/pg_upgrade/pg_upgrade.h               |   5 +
 .../pg_upgrade/t/007_transfer_commit_ts.pl    | 143 ++++++++++++++++++
 6 files changed, 235 insertions(+), 5 deletions(-)
 create mode 100644 src/bin/pg_upgrade/t/007_transfer_commit_ts.pl

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 1e17d64b3ec..b843d7d7e75 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -32,6 +32,7 @@ static void check_new_cluster_replication_slots(void);
 static void check_new_cluster_subscription_configuration(void);
 static void check_old_cluster_for_valid_slots(void);
 static void check_old_cluster_subscription_state(void);
+static void check_new_cluster_pg_commit_ts(void);
 
 /*
  * DataTypesUsageChecks - definitions of data type checks for the old cluster
@@ -695,6 +696,8 @@ check_and_dump_old_cluster(void)
 	if (GET_MAJOR_VERSION(old_cluster.major_version) <= 905)
 		check_for_pg_role_prefix(&old_cluster);
 
+	check_track_commit_timestamp_parameter(&old_cluster);
+
 	/*
 	 * While not a check option, we do this now because this is the only time
 	 * the old server is running.
@@ -767,9 +770,20 @@ check_new_cluster(void)
 	check_new_cluster_replication_slots();
 
 	check_new_cluster_subscription_configuration();
-}
 
+	check_new_cluster_pg_commit_ts();
+
+}
 
+void
+check_new_cluster_pg_commit_ts(void)
+{
+	prep_status("Checking for pg_commit_ts");
+	check_track_commit_timestamp_parameter(&new_cluster);
+	if (old_cluster.track_commit_timestamp_on && !new_cluster.track_commit_timestamp_on)
+		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+	check_ok();
+}
 void
 report_clusters_compatible(void)
 {
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 90cef0864de..b218ed92389 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -208,7 +208,11 @@ get_control_data(ClusterInfo *cluster)
 		cluster->controldata.data_checksum_version = 0;
 		got_data_checksum_version = true;
 	}
-
+	if (GET_MAJOR_VERSION(cluster->major_version) < 905)
+	{
+		cluster->controldata.chkpnt_oldstCommitTsxid = 0;
+		cluster->controldata.chkpnt_newstCommitTsxid = 0;
+	}
 	/* we have the result of cmd in "output". so parse it line by line now */
 	while (fgets(bufin, sizeof(bufin), output))
 	{
@@ -321,6 +325,26 @@ get_control_data(ClusterInfo *cluster)
 			cluster->controldata.chkpnt_nxtmulti = str2uint(p);
 			got_multi = true;
 		}
+		else if ((p = strstr(bufin, "Latest checkpoint's oldestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_oldstCommitTsxid = str2uint(p);
+		}
+		else if ((p = strstr(bufin, "Latest checkpoint's newestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_newstCommitTsxid = str2uint(p);
+		}
 		else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
 		{
 			p = strchr(p, ':');
diff --git a/src/bin/pg_upgrade/info.c b/src/bin/pg_upgrade/info.c
index 7ce08270168..d9b13b25a37 100644
--- a/src/bin/pg_upgrade/info.c
+++ b/src/bin/pg_upgrade/info.c
@@ -819,6 +819,35 @@ get_subscription_info(ClusterInfo *cluster)
 	PQfinish(conn);
 }
 
+/*
+ * check_track_commit_timestamp_parameter(ClusterInfo *cluster)
+ *
+ * Gets track_commit_timestamp parameter in the cluster.
+ */
+void
+check_track_commit_timestamp_parameter(ClusterInfo *cluster)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+	int			is_set;
+
+	/* There is a track_commit_timestamp parameter in 9.5 and above. */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 905)
+	{
+		cluster->track_commit_timestamp_on = false;
+	}
+	else
+	{
+		conn = connectToServer(cluster, "template1");
+		res = executeQueryOrDie(conn, "SELECT count(*) AS is_set "
+								"FROM pg_settings WHERE name = 'track_commit_timestamp' and setting = 'on'");
+		is_set = PQfnumber(res, "is_set");
+		cluster->track_commit_timestamp_on = atoi(PQgetvalue(res, 0, is_set)) == 1;
+
+		PQclear(res);
+		PQfinish(conn);
+	}
+}
 static void
 free_db_and_rel_infos(DbInfoArr *db_arr)
 {
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 490e98fa26f..dc91da78d9b 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -772,6 +772,8 @@ copy_subdir_files(const char *old_subdir, const char *new_subdir)
 static void
 copy_xact_xlog_xid(void)
 {
+	bool		is_copy_commit_ts;
+
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
 	 * pg_xact in post-10 clusters.
@@ -781,6 +783,16 @@ copy_xact_xlog_xid(void)
 					  GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
 					  "pg_clog" : "pg_xact");
 
+	/*
+	 * Copy pg_commit_ts only if three conditions are met
+	 */
+	is_copy_commit_ts = old_cluster.controldata.chkpnt_oldstCommitTsxid > 0
+		&& old_cluster.controldata.chkpnt_newstCommitTsxid > 0
+		&& new_cluster.track_commit_timestamp_on;
+
+	if (is_copy_commit_ts)
+		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -u %u \"%s\"",
@@ -798,12 +810,15 @@ copy_xact_xlog_xid(void)
 			  "\"%s/pg_resetwal\" -f -e %u \"%s\"",
 			  new_cluster.bindir, old_cluster.controldata.chkpnt_nxtepoch,
 			  new_cluster.pgdata);
-	/* must reset commit timestamp limits also */
+
+	/*
+	 * must reset commit timestamp limits also or copy from the old cluster
+	 */
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  old_cluster.controldata.chkpnt_nxtxid,
-			  old_cluster.controldata.chkpnt_nxtxid,
+			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_oldstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
+			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_newstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index 0ef47be0dc1..4bbfdfa881e 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -238,6 +238,8 @@ typedef struct
 	uint32		chkpnt_nxtmxoff;
 	uint32		chkpnt_oldstMulti;
 	uint32		chkpnt_oldstxid;
+	uint32		chkpnt_oldstCommitTsxid;
+	uint32		chkpnt_newstCommitTsxid;
 	uint32		align;
 	uint32		blocksz;
 	uint32		largesz;
@@ -306,6 +308,8 @@ typedef struct
 	int			nsubs;			/* number of subscriptions */
 	bool		sub_retain_dead_tuples; /* whether a subscription enables
 										 * retain_dead_tuples. */
+	bool		track_commit_timestamp_on;	/* track_commit_timestamp for
+										 *    cluster */
 } ClusterInfo;
 
 
@@ -444,6 +448,7 @@ FileNameMap *gen_db_file_maps(DbInfo *old_db,
 void		get_db_rel_and_slot_infos(ClusterInfo *cluster);
 int			count_old_cluster_logical_slots(void);
 void		get_subscription_info(ClusterInfo *cluster);
+void		check_track_commit_timestamp_parameter(ClusterInfo *cluster);
 
 /* option.c */
 
diff --git a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
new file mode 100644
index 00000000000..bbf0e2e1b29
--- /dev/null
+++ b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
@@ -0,0 +1,143 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Tests for transfer pg_commit_ts directory.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+sub command_output
+{
+	my ($cmd) = @_;
+	my ($stdout, $stderr);
+
+	print("# Running: " . join(" ", @{$cmd}) . "\n");
+
+	my $result = IPC::Run::run $cmd, '>', \$stdout, '2>', \$stderr;
+	ok($result, "@$cmd exit code 0");
+	is($stderr, '', "@$cmd no stderr");
+
+	return $stdout;
+}
+
+# Can be changed to test the other modes
+my $mode = $ENV{PG_TEST_PG_UPGRADE_MODE} || '--copy';
+
+# Initialize old cluster
+my $old = PostgreSQL::Test::Cluster->new('old');
+$old->init;
+$old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$old->start;
+$old->command_ok([ 'pgbench', '-i', '-s', '1' ], 'init pgbench');
+$old->command_ok([ 'pgbench', '-t', '100', '-j', '2' ], 'pgbench it');
+$old->stop;
+
+# Initialize new cluster
+my $new = PostgreSQL::Test::Cluster->new('new');
+$new->init;
+command_fails(
+	[
+		'pg_upgrade', '--no-sync',
+		'-d', $old->data_dir,
+		'-D', $new->data_dir,
+		'-b', $old->config_data('--bindir'),
+		'-B', $new->config_data('--bindir'),
+		'-s', $new->host,
+		'-p', $old->port,
+		'-P', $new->port,
+		$mode
+	],
+	'run of pg_upgrade fails with mismatch parameter track_commit_timestamp');
+
+$new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+command_ok(
+	[
+		'pg_upgrade', '--no-sync',
+		'-d', $old->data_dir,
+		'-D', $new->data_dir,
+		'-b', $old->config_data('--bindir'),
+		'-B', $new->config_data('--bindir'),
+		'-s', $new->host,
+		'-p', $old->port,
+		'-P', $new->port,
+		$mode
+	],
+	'run of pg_upgrade ok');
+
+
+$new->start;
+$new->command_ok([ 'pgbench', '-t', '10' ], 'pgbench it');
+$new->stop;
+
+sub xact_commit_ts
+{
+	my ($node) = @_;
+	my ($oldest, $newest);
+	my $out = command_output([ 'pg_controldata', '-D', $node->data_dir ]);
+
+	if ($out =~ /oldestCommitTsXid:(\d+)/) {
+		$oldest = $1;
+	}
+	if ($out =~ /newestCommitTsXid:(\d+)/) {
+		$newest= $1;
+	}
+
+	for my $line (grep { /\S/ } split /\n/, $out) {
+		if ($line =~ /Latest checkpoint's NextXID:/) {
+			print $line . "\n";
+		}
+		if ($line =~ /Latest checkpoint's oldestXID:/) {
+			print $line . "\n";
+		}
+		if ($line =~ /Latest checkpoint's oldestCommitTsXid/) {
+			print $line . "\n";
+		}
+		if ($line =~ /Latest checkpoint's newestCommitTsXid:/) {
+			print $line . "\n";
+		}
+	}
+
+	$node->start;
+	my $res = $node->safe_psql('postgres', "
+	WITH xids AS (
+		SELECT v::text::xid AS x
+		FROM generate_series($oldest, $newest) v
+	)
+	SELECT x, pg_xact_commit_timestamp(x::text::xid)
+	FROM xids;
+	");
+	$node->stop;
+	return grep { /\S/ } split /\n/, $res;
+}
+
+my @a = xact_commit_ts($old);
+my @b = xact_commit_ts($new);
+my %h1 = map { $_ => 1 } @a;
+my %h2 = map { $_ => 1 } @b;
+
+#
+# All timestamps from the old cluster should appear in the new one.
+#
+my $count = 0;
+print "Commit timestamp only in old cluster:\n";
+for my $line (@a) {
+	unless ($h2{$line}) {
+		print "$line\n";
+		$count = $count + 1;
+	}
+}
+ok($count == 0, "all the timestamp transferred successfully");
+
+#
+# The new cluster should contain timestamps created during the pg_upgrade and
+# some more created by the pgbench.
+#
+print "\nCommit timestamp only in new cluster:\n";
+for my $line (@b) {
+	print "$line\n" unless $h1{$line};
+}
+
+done_testing();
-- 
2.42.2

From 1d5499d87687ca15dd7d4daf1b98d68dd11dba74 Mon Sep 17 00:00:00 2001
From: Sergey Levin <ls7777@yandex.ru>
Date: Sat, 4 Oct 2025 20:22:46 +0500
Subject: [PATCH] Migration of the pg_commit_ts directory

---
 src/bin/pg_upgrade/check.c                    |  22 +++
 src/bin/pg_upgrade/controldata.c              |  21 ++-
 src/bin/pg_upgrade/meson.build                |   1 +
 src/bin/pg_upgrade/pg_upgrade.c               |  20 ++-
 src/bin/pg_upgrade/pg_upgrade.h               |   2 +
 .../pg_upgrade/t/007_transfer_commit_ts.pl    | 139 ++++++++++++++++++
 6 files changed, 201 insertions(+), 4 deletions(-)
 create mode 100644 src/bin/pg_upgrade/t/007_transfer_commit_ts.pl

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 1e17d64b3ec..f0e25dd3191 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -32,6 +32,7 @@ static void check_new_cluster_replication_slots(void);
 static void check_new_cluster_subscription_configuration(void);
 static void check_old_cluster_for_valid_slots(void);
 static void check_old_cluster_subscription_state(void);
+static void check_new_cluster_pg_commit_ts(void);
 
 /*
  * DataTypesUsageChecks - definitions of data type checks for the old cluster
@@ -767,9 +768,30 @@ check_new_cluster(void)
 	check_new_cluster_replication_slots();
 
 	check_new_cluster_subscription_configuration();
+
+	check_new_cluster_pg_commit_ts();
+
 }
 
+void
+check_new_cluster_pg_commit_ts(void)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+	bool		track_commit_timestamp_on;
+
+	prep_status("Checking for pg_commit_ts");
+	conn = connectToServer(&new_cluster, "template1");
+	res = executeQueryOrDie(conn, "SELECT setting "
+							"FROM pg_settings WHERE name = 'track_commit_timestamp'");
+	track_commit_timestamp_on = strcmp(PQgetvalue(res, 0, 0), "on") == 0;
+	PQclear(res);
+	PQfinish(conn);
 
+	if (old_cluster.controldata.chkpnt_newstCommitTsxid > 0 && !track_commit_timestamp_on)
+		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+	check_ok();
+}
 void
 report_clusters_compatible(void)
 {
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 90cef0864de..991000265ad 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -208,7 +208,6 @@ get_control_data(ClusterInfo *cluster)
 		cluster->controldata.data_checksum_version = 0;
 		got_data_checksum_version = true;
 	}
-
 	/* we have the result of cmd in "output". so parse it line by line now */
 	while (fgets(bufin, sizeof(bufin), output))
 	{
@@ -321,6 +320,26 @@ get_control_data(ClusterInfo *cluster)
 			cluster->controldata.chkpnt_nxtmulti = str2uint(p);
 			got_multi = true;
 		}
+		else if ((p = strstr(bufin, "Latest checkpoint's oldestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_oldstCommitTsxid = str2uint(p);
+		}
+		else if ((p = strstr(bufin, "Latest checkpoint's newestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_newstCommitTsxid = str2uint(p);
+		}
 		else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
 		{
 			p = strchr(p, ':');
diff --git a/src/bin/pg_upgrade/meson.build b/src/bin/pg_upgrade/meson.build
index ac992f0d14b..030618152d0 100644
--- a/src/bin/pg_upgrade/meson.build
+++ b/src/bin/pg_upgrade/meson.build
@@ -47,6 +47,7 @@ tests += {
       't/004_subscription.pl',
       't/005_char_signedness.pl',
       't/006_transfer_modes.pl',
+      't/007_transfer_commit_ts.pl',
     ],
     'test_kwargs': {'priority': 40}, # pg_upgrade tests are slow
   },
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 490e98fa26f..98d01e8600c 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -772,6 +772,8 @@ copy_subdir_files(const char *old_subdir, const char *new_subdir)
 static void
 copy_xact_xlog_xid(void)
 {
+	bool		is_copy_commit_ts;
+
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
 	 * pg_xact in post-10 clusters.
@@ -781,6 +783,15 @@ copy_xact_xlog_xid(void)
 					  GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
 					  "pg_clog" : "pg_xact");
 
+	/*
+	 * Copy pg_commit_ts
+	 */
+	is_copy_commit_ts = old_cluster.controldata.chkpnt_oldstCommitTsxid > 0
+		&& old_cluster.controldata.chkpnt_newstCommitTsxid > 0;
+
+	if (is_copy_commit_ts)
+		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -u %u \"%s\"",
@@ -798,12 +809,15 @@ copy_xact_xlog_xid(void)
 			  "\"%s/pg_resetwal\" -f -e %u \"%s\"",
 			  new_cluster.bindir, old_cluster.controldata.chkpnt_nxtepoch,
 			  new_cluster.pgdata);
-	/* must reset commit timestamp limits also */
+
+	/*
+	 * must reset commit timestamp limits also or copy from the old cluster
+	 */
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  old_cluster.controldata.chkpnt_nxtxid,
-			  old_cluster.controldata.chkpnt_nxtxid,
+			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_oldstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
+			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_newstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index 0ef47be0dc1..83fdbc44b13 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -238,6 +238,8 @@ typedef struct
 	uint32		chkpnt_nxtmxoff;
 	uint32		chkpnt_oldstMulti;
 	uint32		chkpnt_oldstxid;
+	uint32		chkpnt_oldstCommitTsxid;
+	uint32		chkpnt_newstCommitTsxid;
 	uint32		align;
 	uint32		blocksz;
 	uint32		largesz;
diff --git a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
new file mode 100644
index 00000000000..97d0b88ff2a
--- /dev/null
+++ b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
@@ -0,0 +1,139 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Tests for transfer pg_commit_ts directory.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+sub command_output
+{
+	my ($cmd) = @_;
+	my ($stdout, $stderr);
+
+	print("# Running: " . join(" ", @{$cmd}) . "\n");
+
+	my $result = IPC::Run::run $cmd, '>', \$stdout, '2>', \$stderr;
+	ok($result, "@$cmd exit code 0");
+	is($stderr, '', "@$cmd no stderr");
+
+	return $stdout;
+}
+
+# Can be changed to test the other modes
+my $mode = $ENV{PG_TEST_PG_UPGRADE_MODE} || '--copy';
+
+# Initialize old cluster
+my $old = PostgreSQL::Test::Cluster->new('old');
+$old->init;
+$old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$old->start;
+$old->command_ok([ 'pgbench', '-i', '-s', '1' ], 'init pgbench');
+$old->command_ok([ 'pgbench', '-t', '1', '-j', '1' ], 'pgbench it');
+$old->stop;
+
+# Initialize new cluster
+my $new = PostgreSQL::Test::Cluster->new('new');
+$new->init;
+command_fails(
+	[
+		'pg_upgrade', '--no-sync',
+		'-d', $old->data_dir,
+		'-D', $new->data_dir,
+		'-b', $old->config_data('--bindir'),
+		'-B', $new->config_data('--bindir'),
+		'-s', $new->host,
+		'-p', $old->port,
+		'-P', $new->port,
+		$mode
+	],
+	'run of pg_upgrade fails with mismatch parameter track_commit_timestamp');
+
+$new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+command_ok(
+	[
+		'pg_upgrade', '--no-sync',
+		'-d', $old->data_dir,
+		'-D', $new->data_dir,
+		'-b', $old->config_data('--bindir'),
+		'-B', $new->config_data('--bindir'),
+		'-s', $new->host,
+		'-p', $old->port,
+		'-P', $new->port,
+		$mode
+	],
+	'run of pg_upgrade ok');
+
+
+sub xact_commit_ts
+{
+	my ($node) = @_;
+	my ($oldest, $newest);
+	my $out = command_output([ 'pg_controldata', '-D', $node->data_dir ]);
+
+	if ($out =~ /oldestCommitTsXid:(\d+)/) {
+		$oldest = $1;
+	}
+	if ($out =~ /newestCommitTsXid:(\d+)/) {
+		$newest= $1;
+	}
+
+	for my $line (grep { /\S/ } split /\n/, $out) {
+		if ($line =~ /Latest checkpoint's NextXID:/) {
+			print $line . "\n";
+		}
+		if ($line =~ /Latest checkpoint's oldestXID:/) {
+			print $line . "\n";
+		}
+		if ($line =~ /Latest checkpoint's oldestCommitTsXid/) {
+			print $line . "\n";
+		}
+		if ($line =~ /Latest checkpoint's newestCommitTsXid:/) {
+			print $line . "\n";
+		}
+	}
+
+	$node->start;
+	my $res = $node->safe_psql('postgres', "
+	WITH xids AS (
+		SELECT v::text::xid AS x
+		FROM generate_series($oldest, $newest) v
+	)
+	SELECT x, pg_xact_commit_timestamp(x::text::xid)
+	FROM xids;
+	");
+	$node->stop;
+	return grep { /\S/ } split /\n/, $res;
+}
+
+my @a = xact_commit_ts($old);
+my @b = xact_commit_ts($new);
+my %h1 = map { $_ => 1 } @a;
+my %h2 = map { $_ => 1 } @b;
+
+#
+# All timestamps from the old cluster should appear in the new one.
+#
+my $count = 0;
+print "Commit timestamp only in old cluster:\n";
+for my $line (@a) {
+	unless ($h2{$line}) {
+		print "$line\n";
+		$count = $count + 1;
+	}
+}
+ok($count == 0, "all the timestamp transferred successfully");
+
+#
+# The new cluster should contain timestamps created during the pg_upgrade and
+# some more created by the pgbench.
+#
+print "\nCommit timestamp only in new cluster:\n";
+for my $line (@b) {
+	print "$line\n" unless $h1{$line};
+}
+
+done_testing();
-- 
2.42.2

From 254cae551bbde68c4932d61dc96167fee9f97155 Mon Sep 17 00:00:00 2001
From: Sergey Levin <ls7777@yandex.ru>
Date: Sat, 4 Oct 2025 20:22:46 +0500
Subject: [PATCH] Migration of the pg_commit_ts directory

---
 src/bin/pg_upgrade/check.c                    | 22 ++++++
 src/bin/pg_upgrade/controldata.c              | 20 +++++
 src/bin/pg_upgrade/meson.build                |  1 +
 src/bin/pg_upgrade/pg_upgrade.c               | 20 ++++-
 src/bin/pg_upgrade/pg_upgrade.h               |  2 +
 .../pg_upgrade/t/007_transfer_commit_ts.pl    | 75 +++++++++++++++++++
 6 files changed, 137 insertions(+), 3 deletions(-)
 create mode 100644 src/bin/pg_upgrade/t/007_transfer_commit_ts.pl

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 1e17d64b3ec..c5e29485416 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -32,6 +32,7 @@ static void check_new_cluster_replication_slots(void);
 static void check_new_cluster_subscription_configuration(void);
 static void check_old_cluster_for_valid_slots(void);
 static void check_old_cluster_subscription_state(void);
+static void check_new_cluster_pg_commit_ts(void);
 
 /*
  * DataTypesUsageChecks - definitions of data type checks for the old cluster
@@ -767,9 +768,30 @@ check_new_cluster(void)
 	check_new_cluster_replication_slots();
 
 	check_new_cluster_subscription_configuration();
+
+	check_new_cluster_pg_commit_ts();
+
 }
 
+void
+check_new_cluster_pg_commit_ts(void)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+	bool		track_commit_timestamp_on;
+
+	prep_status("Checking for new cluster configuration for commit timestamp");
+	conn = connectToServer(&new_cluster, "template1");
+	res = executeQueryOrDie(conn, "SELECT setting "
+							"FROM pg_settings WHERE name = 'track_commit_timestamp'");
+	track_commit_timestamp_on = strcmp(PQgetvalue(res, 0, 0), "on") == 0;
+	PQclear(res);
+	PQfinish(conn);
 
+	if (old_cluster.controldata.chkpnt_newstCommitTsxid > 0 && !track_commit_timestamp_on)
+		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+	check_ok();
+}
 void
 report_clusters_compatible(void)
 {
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 90cef0864de..594dc1c0a9f 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -321,6 +321,26 @@ get_control_data(ClusterInfo *cluster)
 			cluster->controldata.chkpnt_nxtmulti = str2uint(p);
 			got_multi = true;
 		}
+		else if ((p = strstr(bufin, "Latest checkpoint's oldestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_oldstCommitTsxid = str2uint(p);
+		}
+		else if ((p = strstr(bufin, "Latest checkpoint's newestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_newstCommitTsxid = str2uint(p);
+		}
 		else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
 		{
 			p = strchr(p, ':');
diff --git a/src/bin/pg_upgrade/meson.build b/src/bin/pg_upgrade/meson.build
index ac992f0d14b..030618152d0 100644
--- a/src/bin/pg_upgrade/meson.build
+++ b/src/bin/pg_upgrade/meson.build
@@ -47,6 +47,7 @@ tests += {
       't/004_subscription.pl',
       't/005_char_signedness.pl',
       't/006_transfer_modes.pl',
+      't/007_transfer_commit_ts.pl',
     ],
     'test_kwargs': {'priority': 40}, # pg_upgrade tests are slow
   },
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 490e98fa26f..c46a4432fd2 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -772,6 +772,8 @@ copy_subdir_files(const char *old_subdir, const char *new_subdir)
 static void
 copy_xact_xlog_xid(void)
 {
+	bool		is_copy_commit_ts;
+
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
 	 * pg_xact in post-10 clusters.
@@ -781,6 +783,15 @@ copy_xact_xlog_xid(void)
 					  GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
 					  "pg_clog" : "pg_xact");
 
+	/*
+	 * Copy old commit_timestamp data to new, if available.
+	 */
+	is_copy_commit_ts = old_cluster.controldata.chkpnt_oldstCommitTsxid > 0
+		&& old_cluster.controldata.chkpnt_newstCommitTsxid > 0;
+
+	if (is_copy_commit_ts)
+		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -u %u \"%s\"",
@@ -798,12 +809,15 @@ copy_xact_xlog_xid(void)
 			  "\"%s/pg_resetwal\" -f -e %u \"%s\"",
 			  new_cluster.bindir, old_cluster.controldata.chkpnt_nxtepoch,
 			  new_cluster.pgdata);
-	/* must reset commit timestamp limits also */
+
+	/*
+	 * must reset commit timestamp limits also or copy from the old cluster
+	 */
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  old_cluster.controldata.chkpnt_nxtxid,
-			  old_cluster.controldata.chkpnt_nxtxid,
+			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_oldstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
+			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_newstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index 0ef47be0dc1..83fdbc44b13 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -238,6 +238,8 @@ typedef struct
 	uint32		chkpnt_nxtmxoff;
 	uint32		chkpnt_oldstMulti;
 	uint32		chkpnt_oldstxid;
+	uint32		chkpnt_oldstCommitTsxid;
+	uint32		chkpnt_newstCommitTsxid;
 	uint32		align;
 	uint32		blocksz;
 	uint32		largesz;
diff --git a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
new file mode 100644
index 00000000000..1b75bf17e8c
--- /dev/null
+++ b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
@@ -0,0 +1,75 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Tests for transfer pg_commit_ts directory.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Can be changed to test the other modes
+my $mode = $ENV{PG_TEST_PG_UPGRADE_MODE} || '--copy';
+
+# Initialize old cluster
+my $old = PostgreSQL::Test::Cluster->new('old');
+$old->init;
+$old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$old->start;
+my $resold = $old->safe_psql('postgres', "
+		create table a(a int);
+                select xid,timestamp from pg_last_committed_xact();
+	");
+
+my ($xid,$ts) = $resold =~ /\s*(\d+)\s*\|(.*)/;
+$old->stop;
+
+# Initialize new cluster
+my $new = PostgreSQL::Test::Cluster->new('new');
+$new->init;
+command_checks_all(
+	[
+		'pg_upgrade', '--no-sync',
+		'--old-datadir' => $old->data_dir,
+		'--new-datadir' => $new->data_dir,
+		'--old-bindir' => $old->config_data('--bindir'),
+		'--new-bindir' => $new->config_data('--bindir'),
+		'--socketdir' => $new->host,
+		'--old-port' => $old->port,
+		'--new-port' => $new->port,
+		$mode
+	],
+	1,
+	[qr{"track_commit_timestamp" must be "on" but is set to "off"}],
+	[],
+	'run of pg_upgrade for mismatch parameter track_commit_timestamp');
+
+
+$new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+
+command_checks_all(
+	[
+		'pg_upgrade', '--no-sync',
+		'--old-datadir' => $old->data_dir,
+		'--new-datadir' => $new->data_dir,
+		'--old-bindir' => $old->config_data('--bindir'),
+		'--new-bindir' => $new->config_data('--bindir'),
+		'--socketdir' => $new->host,
+		'--old-port' => $old->port,
+		'--new-port' => $new->port,
+		$mode
+	],
+	0,
+	[],
+	[],
+	'run of pg_upgrade ok');
+
+$new->start;
+my $resnew = $new->safe_psql('postgres', "
+                select $xid,pg_xact_commit_timestamp(${xid}::text::xid);
+	");
+$new->stop;
+ok($resold eq $resnew, "timestamp transferred successfully");
+
+done_testing();
-- 
2.42.2

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index c5e29485416..382da0485a7 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -782,14 +782,16 @@ check_new_cluster_pg_commit_ts(void)
 
 	prep_status("Checking for new cluster configuration for commit timestamp");
 	conn = connectToServer(&new_cluster, "template1");
-	res = executeQueryOrDie(conn, "SELECT setting "
-							"FROM pg_settings WHERE name = 'track_commit_timestamp'");
+	res = executeQueryOrDie(conn, "SELECT setting FROM pg_settings "
+								  "WHERE name = 'track_commit_timestamp'");
 	track_commit_timestamp_on = strcmp(PQgetvalue(res, 0, 0), "on") == 0;
 	PQclear(res);
 	PQfinish(conn);
 
-	if (old_cluster.controldata.chkpnt_newstCommitTsxid > 0 && !track_commit_timestamp_on)
+	if (!track_commit_timestamp_on &&
+		old_cluster.controldata.chkpnt_newstCommitTsxid > 0)
 		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+
 	check_ok();
 }
 void
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index c46a4432fd2..70297f38dca 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -773,6 +773,7 @@ static void
 copy_xact_xlog_xid(void)
 {
 	bool		is_copy_commit_ts;
+	uint32		oldest_xid, newest_xid;
 
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
@@ -786,11 +787,18 @@ copy_xact_xlog_xid(void)
 	/*
 	 * Copy old commit_timestamp data to new, if available.
 	 */
-	is_copy_commit_ts = old_cluster.controldata.chkpnt_oldstCommitTsxid > 0
-		&& old_cluster.controldata.chkpnt_newstCommitTsxid > 0;
+	is_copy_commit_ts =
+		(old_cluster.controldata.chkpnt_oldstCommitTsxid > 0 &&
+		 old_cluster.controldata.chkpnt_newstCommitTsxid > 0);
 
 	if (is_copy_commit_ts)
+	{
 		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+		oldest_xid = old_cluster.controldata.chkpnt_oldstCommitTsxid;
+		newest_xid = old_cluster.controldata.chkpnt_newstCommitTsxid;
+	}
+	else
+		oldest_xid = newest_xid = old_cluster.controldata.chkpnt_nxtxid;
 
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
@@ -816,8 +824,8 @@ copy_xact_xlog_xid(void)
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_oldstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
-			  is_copy_commit_ts ? old_cluster.controldata.chkpnt_newstCommitTsxid : old_cluster.controldata.chkpnt_nxtxid,
+			  oldest_xid,
+			  newest_xid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
index 1b75bf17e8c..c67463ab961 100644
--- a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
+++ b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
@@ -17,58 +17,50 @@ my $old = PostgreSQL::Test::Cluster->new('old');
 $old->init;
 $old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 $old->start;
-my $resold = $old->safe_psql('postgres', "
+my $resold = $old->safe_psql(
+	'postgres', qq{
 		create table a(a int);
-                select xid,timestamp from pg_last_committed_xact();
-	");
+		select xid,timestamp from pg_last_committed_xact();
+});
 
-my ($xid,$ts) = $resold =~ /\s*(\d+)\s*\|(.*)/;
+my ($xid, $ts) = $resold =~ /\s*(\d+)\s*\|(.*)/;
 $old->stop;
 
 # Initialize new cluster
 my $new = PostgreSQL::Test::Cluster->new('new');
 $new->init;
+
+# Setup a common pg_upgrade command to be used by all the test cases
+my @pg_upgrade_cmd = (
+	'pg_upgrade', '--no-sync',
+	'--old-datadir' => $old->data_dir,
+	'--new-datadir' => $new->data_dir,
+	'--old-bindir' => $old->config_data('--bindir'),
+	'--new-bindir' => $new->config_data('--bindir'),
+	'--socketdir' => $new->host,
+	'--old-port' => $old->port,
+	'--new-port' => $new->port,
+	$mode);
+
+# In a VPATH build, we'll be started in the source directory, but we want
+# to run pg_upgrade in the build directory so that any files generated finish
+# in it, like delete_old_cluster.{sh,bat}.
+chdir ${PostgreSQL::Test::Utils::tmp_check};
+
 command_checks_all(
-	[
-		'pg_upgrade', '--no-sync',
-		'--old-datadir' => $old->data_dir,
-		'--new-datadir' => $new->data_dir,
-		'--old-bindir' => $old->config_data('--bindir'),
-		'--new-bindir' => $new->config_data('--bindir'),
-		'--socketdir' => $new->host,
-		'--old-port' => $old->port,
-		'--new-port' => $new->port,
-		$mode
-	],
-	1,
-	[qr{"track_commit_timestamp" must be "on" but is set to "off"}],
-	[],
+	[@pg_upgrade_cmd], 1,
+	[qr{"track_commit_timestamp" must be "on" but is set to "off"}], [],
 	'run of pg_upgrade for mismatch parameter track_commit_timestamp');
 
-
 $new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
 
-command_checks_all(
-	[
-		'pg_upgrade', '--no-sync',
-		'--old-datadir' => $old->data_dir,
-		'--new-datadir' => $new->data_dir,
-		'--old-bindir' => $old->config_data('--bindir'),
-		'--new-bindir' => $new->config_data('--bindir'),
-		'--socketdir' => $new->host,
-		'--old-port' => $old->port,
-		'--new-port' => $new->port,
-		$mode
-	],
-	0,
-	[],
-	[],
-	'run of pg_upgrade ok');
+command_ok([@pg_upgrade_cmd], 'run of pg_upgrade ok');
 
 $new->start;
-my $resnew = $new->safe_psql('postgres', "
-                select $xid,pg_xact_commit_timestamp(${xid}::text::xid);
-	");
+my $resnew = $new->safe_psql(
+	'postgres', qq{
+	select $xid,pg_xact_commit_timestamp(${xid}::text::xid);
+});
 $new->stop;
 ok($resold eq $resnew, "timestamp transferred successfully");
 

From bc582227cdd51d252db00fccc4d572524f9a4b91 Mon Sep 17 00:00:00 2001
From: Sergey Levin <ls7777@yandex.ru>
Date: Sat, 4 Oct 2025 20:22:46 +0500
Subject: [PATCH] Migration of the pg_commit_ts directory

---
 src/bin/pg_upgrade/check.c                    | 24 +++++++
 src/bin/pg_upgrade/controldata.c              | 20 ++++++
 src/bin/pg_upgrade/meson.build                |  1 +
 src/bin/pg_upgrade/pg_upgrade.c               | 28 +++++++-
 src/bin/pg_upgrade/pg_upgrade.h               |  2 +
 .../pg_upgrade/t/007_transfer_commit_ts.pl    | 67 +++++++++++++++++++
 6 files changed, 139 insertions(+), 3 deletions(-)
 create mode 100644 src/bin/pg_upgrade/t/007_transfer_commit_ts.pl

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 1e17d64b3ec..382da0485a7 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -32,6 +32,7 @@ static void check_new_cluster_replication_slots(void);
 static void check_new_cluster_subscription_configuration(void);
 static void check_old_cluster_for_valid_slots(void);
 static void check_old_cluster_subscription_state(void);
+static void check_new_cluster_pg_commit_ts(void);
 
 /*
  * DataTypesUsageChecks - definitions of data type checks for the old cluster
@@ -767,9 +768,32 @@ check_new_cluster(void)
 	check_new_cluster_replication_slots();
 
 	check_new_cluster_subscription_configuration();
+
+	check_new_cluster_pg_commit_ts();
+
 }
 
+void
+check_new_cluster_pg_commit_ts(void)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+	bool		track_commit_timestamp_on;
+
+	prep_status("Checking for new cluster configuration for commit timestamp");
+	conn = connectToServer(&new_cluster, "template1");
+	res = executeQueryOrDie(conn, "SELECT setting FROM pg_settings "
+								  "WHERE name = 'track_commit_timestamp'");
+	track_commit_timestamp_on = strcmp(PQgetvalue(res, 0, 0), "on") == 0;
+	PQclear(res);
+	PQfinish(conn);
 
+	if (!track_commit_timestamp_on &&
+		old_cluster.controldata.chkpnt_newstCommitTsxid > 0)
+		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+
+	check_ok();
+}
 void
 report_clusters_compatible(void)
 {
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 90cef0864de..594dc1c0a9f 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -321,6 +321,26 @@ get_control_data(ClusterInfo *cluster)
 			cluster->controldata.chkpnt_nxtmulti = str2uint(p);
 			got_multi = true;
 		}
+		else if ((p = strstr(bufin, "Latest checkpoint's oldestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_oldstCommitTsxid = str2uint(p);
+		}
+		else if ((p = strstr(bufin, "Latest checkpoint's newestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_newstCommitTsxid = str2uint(p);
+		}
 		else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
 		{
 			p = strchr(p, ':');
diff --git a/src/bin/pg_upgrade/meson.build b/src/bin/pg_upgrade/meson.build
index ac992f0d14b..030618152d0 100644
--- a/src/bin/pg_upgrade/meson.build
+++ b/src/bin/pg_upgrade/meson.build
@@ -47,6 +47,7 @@ tests += {
       't/004_subscription.pl',
       't/005_char_signedness.pl',
       't/006_transfer_modes.pl',
+      't/007_transfer_commit_ts.pl',
     ],
     'test_kwargs': {'priority': 40}, # pg_upgrade tests are slow
   },
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 490e98fa26f..70297f38dca 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -772,6 +772,9 @@ copy_subdir_files(const char *old_subdir, const char *new_subdir)
 static void
 copy_xact_xlog_xid(void)
 {
+	bool		is_copy_commit_ts;
+	uint32		oldest_xid, newest_xid;
+
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
 	 * pg_xact in post-10 clusters.
@@ -781,6 +784,22 @@ copy_xact_xlog_xid(void)
 					  GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
 					  "pg_clog" : "pg_xact");
 
+	/*
+	 * Copy old commit_timestamp data to new, if available.
+	 */
+	is_copy_commit_ts =
+		(old_cluster.controldata.chkpnt_oldstCommitTsxid > 0 &&
+		 old_cluster.controldata.chkpnt_newstCommitTsxid > 0);
+
+	if (is_copy_commit_ts)
+	{
+		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+		oldest_xid = old_cluster.controldata.chkpnt_oldstCommitTsxid;
+		newest_xid = old_cluster.controldata.chkpnt_newstCommitTsxid;
+	}
+	else
+		oldest_xid = newest_xid = old_cluster.controldata.chkpnt_nxtxid;
+
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -u %u \"%s\"",
@@ -798,12 +817,15 @@ copy_xact_xlog_xid(void)
 			  "\"%s/pg_resetwal\" -f -e %u \"%s\"",
 			  new_cluster.bindir, old_cluster.controldata.chkpnt_nxtepoch,
 			  new_cluster.pgdata);
-	/* must reset commit timestamp limits also */
+
+	/*
+	 * must reset commit timestamp limits also or copy from the old cluster
+	 */
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  old_cluster.controldata.chkpnt_nxtxid,
-			  old_cluster.controldata.chkpnt_nxtxid,
+			  oldest_xid,
+			  newest_xid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index 0ef47be0dc1..83fdbc44b13 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -238,6 +238,8 @@ typedef struct
 	uint32		chkpnt_nxtmxoff;
 	uint32		chkpnt_oldstMulti;
 	uint32		chkpnt_oldstxid;
+	uint32		chkpnt_oldstCommitTsxid;
+	uint32		chkpnt_newstCommitTsxid;
 	uint32		align;
 	uint32		blocksz;
 	uint32		largesz;
diff --git a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
new file mode 100644
index 00000000000..e4ae1d951fa
--- /dev/null
+++ b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
@@ -0,0 +1,67 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Tests for transfer pg_commit_ts directory.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Can be changed to test the other modes
+my $mode = $ENV{PG_TEST_PG_UPGRADE_MODE} || '--copy';
+
+# Initialize old cluster
+my $old = PostgreSQL::Test::Cluster->new('old');
+$old->init;
+$old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$old->start;
+my $resold = $old->safe_psql(
+	'postgres', qq{
+		create table a(a int);
+		select xid,timestamp from pg_last_committed_xact();
+});
+
+my ($xid) = $resold =~ /\s*(\d+)\s*\|.*/;
+$old->stop;
+
+# Initialize new cluster
+my $new = PostgreSQL::Test::Cluster->new('new');
+$new->init;
+
+# Setup a common pg_upgrade command to be used by all the test cases
+my @pg_upgrade_cmd = (
+	'pg_upgrade', '--no-sync',
+	'--old-datadir' => $old->data_dir,
+	'--new-datadir' => $new->data_dir,
+	'--old-bindir' => $old->config_data('--bindir'),
+	'--new-bindir' => $new->config_data('--bindir'),
+	'--socketdir' => $new->host,
+	'--old-port' => $old->port,
+	'--new-port' => $new->port,
+	$mode);
+
+# In a VPATH build, we'll be started in the source directory, but we want
+# to run pg_upgrade in the build directory so that any files generated finish
+# in it, like delete_old_cluster.{sh,bat}.
+chdir ${PostgreSQL::Test::Utils::tmp_check};
+
+command_checks_all(
+	[@pg_upgrade_cmd], 1,
+	[qr{"track_commit_timestamp" must be "on" but is set to "off"}], [],
+	'run of pg_upgrade for mismatch parameter track_commit_timestamp');
+
+$new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+
+command_ok([@pg_upgrade_cmd], 'run of pg_upgrade ok');
+
+$new->start;
+my $resnew = $new->safe_psql(
+	'postgres', qq{
+	select $xid,pg_xact_commit_timestamp(${xid}::text::xid);
+});
+$new->stop;
+ok($resold eq $resnew, "timestamp transferred successfully");
+
+done_testing();
-- 
2.42.2

From b8f529a6ed706e5064f3962d77c0d3128534947c Mon Sep 17 00:00:00 2001
From: Sergey Levin <ls7777@yandex.ru>
Date: Sat, 4 Oct 2025 20:22:46 +0500
Subject: [PATCH v7] Migration of the pg_commit_ts directory

---
 src/bin/pg_upgrade/check.c                    | 24 +++++++
 src/bin/pg_upgrade/controldata.c              | 20 ++++++
 src/bin/pg_upgrade/meson.build                |  1 +
 src/bin/pg_upgrade/pg_upgrade.c               | 29 +++++++-
 src/bin/pg_upgrade/pg_upgrade.h               |  2 +
 .../pg_upgrade/t/007_transfer_commit_ts.pl    | 67 +++++++++++++++++++
 6 files changed, 140 insertions(+), 3 deletions(-)
 create mode 100644 src/bin/pg_upgrade/t/007_transfer_commit_ts.pl

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 1e17d64b3ec..73c69236d4d 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -32,6 +32,7 @@ static void check_new_cluster_replication_slots(void);
 static void check_new_cluster_subscription_configuration(void);
 static void check_old_cluster_for_valid_slots(void);
 static void check_old_cluster_subscription_state(void);
+static void check_new_cluster_pg_commit_ts(void);
 
 /*
  * DataTypesUsageChecks - definitions of data type checks for the old cluster
@@ -767,9 +768,32 @@ check_new_cluster(void)
 	check_new_cluster_replication_slots();
 
 	check_new_cluster_subscription_configuration();
+
+	check_new_cluster_pg_commit_ts();
+
 }
 
+void
+check_new_cluster_pg_commit_ts(void)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+	bool		track_commit_timestamp_on;
+
+	prep_status("Checking for new cluster configuration for commit timestamp");
+	conn = connectToServer(&new_cluster, "template1");
+	res = executeQueryOrDie(conn, "SELECT setting FROM pg_settings "
+							"WHERE name = 'track_commit_timestamp'");
+	track_commit_timestamp_on = strcmp(PQgetvalue(res, 0, 0), "on") == 0;
+	PQclear(res);
+	PQfinish(conn);
 
+	if (!track_commit_timestamp_on &&
+		old_cluster.controldata.chkpnt_newstCommitTsxid > 0)
+		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+
+	check_ok();
+}
 void
 report_clusters_compatible(void)
 {
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index 90cef0864de..594dc1c0a9f 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -321,6 +321,26 @@ get_control_data(ClusterInfo *cluster)
 			cluster->controldata.chkpnt_nxtmulti = str2uint(p);
 			got_multi = true;
 		}
+		else if ((p = strstr(bufin, "Latest checkpoint's oldestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_oldstCommitTsxid = str2uint(p);
+		}
+		else if ((p = strstr(bufin, "Latest checkpoint's newestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_newstCommitTsxid = str2uint(p);
+		}
 		else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
 		{
 			p = strchr(p, ':');
diff --git a/src/bin/pg_upgrade/meson.build b/src/bin/pg_upgrade/meson.build
index ac992f0d14b..030618152d0 100644
--- a/src/bin/pg_upgrade/meson.build
+++ b/src/bin/pg_upgrade/meson.build
@@ -47,6 +47,7 @@ tests += {
       't/004_subscription.pl',
       't/005_char_signedness.pl',
       't/006_transfer_modes.pl',
+      't/007_transfer_commit_ts.pl',
     ],
     'test_kwargs': {'priority': 40}, # pg_upgrade tests are slow
   },
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 490e98fa26f..3566a2a75bc 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -772,6 +772,10 @@ copy_subdir_files(const char *old_subdir, const char *new_subdir)
 static void
 copy_xact_xlog_xid(void)
 {
+	bool		is_copy_commit_ts;
+	uint32		oldest_xid,
+				newest_xid;
+
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
 	 * pg_xact in post-10 clusters.
@@ -781,6 +785,22 @@ copy_xact_xlog_xid(void)
 					  GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
 					  "pg_clog" : "pg_xact");
 
+	/*
+	 * Copy old commit_timestamp data to new, if available.
+	 */
+	is_copy_commit_ts =
+		(old_cluster.controldata.chkpnt_oldstCommitTsxid > 0 &&
+		 old_cluster.controldata.chkpnt_newstCommitTsxid > 0);
+
+	if (is_copy_commit_ts)
+	{
+		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+		oldest_xid = old_cluster.controldata.chkpnt_oldstCommitTsxid;
+		newest_xid = old_cluster.controldata.chkpnt_newstCommitTsxid;
+	}
+	else
+		oldest_xid = newest_xid = old_cluster.controldata.chkpnt_nxtxid;
+
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -u %u \"%s\"",
@@ -798,12 +818,15 @@ copy_xact_xlog_xid(void)
 			  "\"%s/pg_resetwal\" -f -e %u \"%s\"",
 			  new_cluster.bindir, old_cluster.controldata.chkpnt_nxtepoch,
 			  new_cluster.pgdata);
-	/* must reset commit timestamp limits also */
+
+	/*
+	 * must reset commit timestamp limits also or copy from the old cluster
+	 */
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  old_cluster.controldata.chkpnt_nxtxid,
-			  old_cluster.controldata.chkpnt_nxtxid,
+			  oldest_xid,
+			  newest_xid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index e86336f4be9..ccc391311a3 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -238,6 +238,8 @@ typedef struct
 	uint32		chkpnt_nxtmxoff;
 	uint32		chkpnt_oldstMulti;
 	uint32		chkpnt_oldstxid;
+	uint32		chkpnt_oldstCommitTsxid;
+	uint32		chkpnt_newstCommitTsxid;
 	uint32		align;
 	uint32		blocksz;
 	uint32		largesz;
diff --git a/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
new file mode 100644
index 00000000000..e4ae1d951fa
--- /dev/null
+++ b/src/bin/pg_upgrade/t/007_transfer_commit_ts.pl
@@ -0,0 +1,67 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Tests for transfer pg_commit_ts directory.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Can be changed to test the other modes
+my $mode = $ENV{PG_TEST_PG_UPGRADE_MODE} || '--copy';
+
+# Initialize old cluster
+my $old = PostgreSQL::Test::Cluster->new('old');
+$old->init;
+$old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$old->start;
+my $resold = $old->safe_psql(
+	'postgres', qq{
+		create table a(a int);
+		select xid,timestamp from pg_last_committed_xact();
+});
+
+my ($xid) = $resold =~ /\s*(\d+)\s*\|.*/;
+$old->stop;
+
+# Initialize new cluster
+my $new = PostgreSQL::Test::Cluster->new('new');
+$new->init;
+
+# Setup a common pg_upgrade command to be used by all the test cases
+my @pg_upgrade_cmd = (
+	'pg_upgrade', '--no-sync',
+	'--old-datadir' => $old->data_dir,
+	'--new-datadir' => $new->data_dir,
+	'--old-bindir' => $old->config_data('--bindir'),
+	'--new-bindir' => $new->config_data('--bindir'),
+	'--socketdir' => $new->host,
+	'--old-port' => $old->port,
+	'--new-port' => $new->port,
+	$mode);
+
+# In a VPATH build, we'll be started in the source directory, but we want
+# to run pg_upgrade in the build directory so that any files generated finish
+# in it, like delete_old_cluster.{sh,bat}.
+chdir ${PostgreSQL::Test::Utils::tmp_check};
+
+command_checks_all(
+	[@pg_upgrade_cmd], 1,
+	[qr{"track_commit_timestamp" must be "on" but is set to "off"}], [],
+	'run of pg_upgrade for mismatch parameter track_commit_timestamp');
+
+$new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+
+command_ok([@pg_upgrade_cmd], 'run of pg_upgrade ok');
+
+$new->start;
+my $resnew = $new->safe_psql(
+	'postgres', qq{
+	select $xid,pg_xact_commit_timestamp(${xid}::text::xid);
+});
+$new->stop;
+ok($resold eq $resnew, "timestamp transferred successfully");
+
+done_testing();
-- 
2.47.3

From 53cde45863d0fa00c6dc84a3dd02ab10a622b6bd Mon Sep 17 00:00:00 2001
From: Sergey Levin <ls7777@yandex.ru>
Date: Sat, 4 Oct 2025 20:22:46 +0500
Subject: [PATCH v8] Migration of the pg_commit_ts directory

---
 src/bin/pg_upgrade/check.c                    | 24 +++++++
 src/bin/pg_upgrade/controldata.c              | 20 ++++++
 src/bin/pg_upgrade/meson.build                |  1 +
 src/bin/pg_upgrade/pg_upgrade.c               | 29 +++++++-
 src/bin/pg_upgrade/pg_upgrade.h               |  2 +
 .../pg_upgrade/t/008_transfer_commit_ts.pl    | 67 +++++++++++++++++++
 6 files changed, 140 insertions(+), 3 deletions(-)
 create mode 100644 src/bin/pg_upgrade/t/008_transfer_commit_ts.pl

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index a47d553b809..fc0b720b60c 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -32,6 +32,7 @@ static void check_new_cluster_replication_slots(void);
 static void check_new_cluster_subscription_configuration(void);
 static void check_old_cluster_for_valid_slots(void);
 static void check_old_cluster_subscription_state(void);
+static void check_new_cluster_pg_commit_ts(void);
 
 /*
  * DataTypesUsageChecks - definitions of data type checks for the old cluster
@@ -767,9 +768,32 @@ check_new_cluster(void)
 	check_new_cluster_replication_slots();
 
 	check_new_cluster_subscription_configuration();
+
+	check_new_cluster_pg_commit_ts();
+
 }
 
+void
+check_new_cluster_pg_commit_ts(void)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+	bool		track_commit_timestamp_on;
+
+	prep_status("Checking for new cluster configuration for commit timestamp");
+	conn = connectToServer(&new_cluster, "template1");
+	res = executeQueryOrDie(conn, "SELECT setting FROM pg_settings "
+							"WHERE name = 'track_commit_timestamp'");
+	track_commit_timestamp_on = strcmp(PQgetvalue(res, 0, 0), "on") == 0;
+	PQclear(res);
+	PQfinish(conn);
 
+	if (!track_commit_timestamp_on &&
+		old_cluster.controldata.chkpnt_newstCommitTsxid > 0)
+		pg_fatal("\"track_commit_timestamp\" must be \"on\" but is set to \"off\"");
+
+	check_ok();
+}
 void
 report_clusters_compatible(void)
 {
diff --git a/src/bin/pg_upgrade/controldata.c b/src/bin/pg_upgrade/controldata.c
index aa6e8b4de5d..fa8b28adf43 100644
--- a/src/bin/pg_upgrade/controldata.c
+++ b/src/bin/pg_upgrade/controldata.c
@@ -321,6 +321,26 @@ get_control_data(ClusterInfo *cluster)
 			cluster->controldata.chkpnt_nxtmulti = str2uint(p);
 			got_multi = true;
 		}
+		else if ((p = strstr(bufin, "Latest checkpoint's oldestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_oldstCommitTsxid = str2uint(p);
+		}
+		else if ((p = strstr(bufin, "Latest checkpoint's newestCommitTsXid:")) != NULL)
+		{
+			p = strchr(p, ':');
+
+			if (p == NULL || strlen(p) <= 1)
+				pg_fatal("%d: controldata retrieval problem", __LINE__);
+
+			p++;				/* remove ':' char */
+			cluster->controldata.chkpnt_newstCommitTsxid = str2uint(p);
+		}
 		else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
 		{
 			p = strchr(p, ':');
diff --git a/src/bin/pg_upgrade/meson.build b/src/bin/pg_upgrade/meson.build
index 49b1b624f25..b27477c3f8a 100644
--- a/src/bin/pg_upgrade/meson.build
+++ b/src/bin/pg_upgrade/meson.build
@@ -51,6 +51,7 @@ tests += {
       't/005_char_signedness.pl',
       't/006_transfer_modes.pl',
       't/007_multixact_conversion.pl',
+      't/008_transfer_commit_ts.pl',
     ],
     'test_kwargs': {'priority': 40}, # pg_upgrade tests are slow
   },
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 2127d297bfe..b761f6c86c4 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -773,6 +773,10 @@ copy_subdir_files(const char *old_subdir, const char *new_subdir)
 static void
 copy_xact_xlog_xid(void)
 {
+	bool		is_copy_commit_ts;
+	uint32		oldest_xid,
+				newest_xid;
+
 	/*
 	 * Copy old commit logs to new data dir. pg_clog has been renamed to
 	 * pg_xact in post-10 clusters.
@@ -782,6 +786,22 @@ copy_xact_xlog_xid(void)
 					  GET_MAJOR_VERSION(new_cluster.major_version) <= 906 ?
 					  "pg_clog" : "pg_xact");
 
+	/*
+	 * Copy old commit_timestamp data to new, if available.
+	 */
+	is_copy_commit_ts =
+		(old_cluster.controldata.chkpnt_oldstCommitTsxid > 0 &&
+		 old_cluster.controldata.chkpnt_newstCommitTsxid > 0);
+
+	if (is_copy_commit_ts)
+	{
+		copy_subdir_files("pg_commit_ts", "pg_commit_ts");
+		oldest_xid = old_cluster.controldata.chkpnt_oldstCommitTsxid;
+		newest_xid = old_cluster.controldata.chkpnt_newstCommitTsxid;
+	}
+	else
+		oldest_xid = newest_xid = old_cluster.controldata.chkpnt_nxtxid;
+
 	prep_status("Setting oldest XID for new cluster");
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -u %u \"%s\"",
@@ -799,12 +819,15 @@ copy_xact_xlog_xid(void)
 			  "\"%s/pg_resetwal\" -f -e %u \"%s\"",
 			  new_cluster.bindir, old_cluster.controldata.chkpnt_nxtepoch,
 			  new_cluster.pgdata);
-	/* must reset commit timestamp limits also */
+
+	/*
+	 * must reset commit timestamp limits also or copy from the old cluster
+	 */
 	exec_prog(UTILITY_LOG_FILE, NULL, true, true,
 			  "\"%s/pg_resetwal\" -f -c %u,%u \"%s\"",
 			  new_cluster.bindir,
-			  old_cluster.controldata.chkpnt_nxtxid,
-			  old_cluster.controldata.chkpnt_nxtxid,
+			  oldest_xid,
+			  newest_xid,
 			  new_cluster.pgdata);
 	check_ok();
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index ec018e4f292..938413521cd 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -245,6 +245,8 @@ typedef struct
 	uint64		chkpnt_nxtmxoff;
 	uint32		chkpnt_oldstMulti;
 	uint32		chkpnt_oldstxid;
+	uint32		chkpnt_oldstCommitTsxid;
+	uint32		chkpnt_newstCommitTsxid;
 	uint32		align;
 	uint32		blocksz;
 	uint32		largesz;
diff --git a/src/bin/pg_upgrade/t/008_transfer_commit_ts.pl b/src/bin/pg_upgrade/t/008_transfer_commit_ts.pl
new file mode 100644
index 00000000000..a9f0ff4ba8f
--- /dev/null
+++ b/src/bin/pg_upgrade/t/008_transfer_commit_ts.pl
@@ -0,0 +1,67 @@
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+# Tests for transfer pg_commit_ts directory.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Can be changed to test the other modes
+my $mode = $ENV{PG_TEST_PG_UPGRADE_MODE} || '--copy';
+
+# Initialize old cluster
+my $old = PostgreSQL::Test::Cluster->new('old');
+$old->init;
+$old->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+$old->start;
+my $resold = $old->safe_psql(
+	'postgres', qq{
+		create table a(a int);
+		select xid,timestamp from pg_last_committed_xact();
+});
+
+my ($xid) = $resold =~ /\s*(\d+)\s*\|.*/;
+$old->stop;
+
+# Initialize new cluster
+my $new = PostgreSQL::Test::Cluster->new('new');
+$new->init;
+
+# Setup a common pg_upgrade command to be used by all the test cases
+my @pg_upgrade_cmd = (
+	'pg_upgrade', '--no-sync',
+	'--old-datadir' => $old->data_dir,
+	'--new-datadir' => $new->data_dir,
+	'--old-bindir' => $old->config_data('--bindir'),
+	'--new-bindir' => $new->config_data('--bindir'),
+	'--socketdir' => $new->host,
+	'--old-port' => $old->port,
+	'--new-port' => $new->port,
+	$mode);
+
+# In a VPATH build, we'll be started in the source directory, but we want
+# to run pg_upgrade in the build directory so that any files generated finish
+# in it, like delete_old_cluster.{sh,bat}.
+chdir ${PostgreSQL::Test::Utils::tmp_check};
+
+command_checks_all(
+	[@pg_upgrade_cmd], 1,
+	[qr{"track_commit_timestamp" must be "on" but is set to "off"}], [],
+	'run of pg_upgrade for mismatch parameter track_commit_timestamp');
+
+$new->append_conf('postgresql.conf', 'track_commit_timestamp = on');
+
+command_ok([@pg_upgrade_cmd], 'run of pg_upgrade ok');
+
+$new->start;
+my $resnew = $new->safe_psql(
+	'postgres', qq{
+	select $xid,pg_xact_commit_timestamp(${xid}::text::xid);
+});
+$new->stop;
+ok($resold eq $resnew, "timestamp transferred successfully");
+
+done_testing();
-- 
2.47.3