From e81b766c3589d05c7284c596148baeaa4ee5114e Mon Sep 17 00:00:00 2001
From: Zhijie Hou <houzj.fnst@cn.fujitsu.com>
Date: Mon, 26 May 2025 14:27:19 +0800
Subject: [PATCH v32 4/7] Introduce a new GUC 'max_conflict_retention_duration'

This commit introduces a GUC option max_conflict_retention_duration, designed
to prevent excessive accumulation of dead tuples when subscription with
retain_conflict_info enabled is present and the the apply worker cannot catch
up with the publisher's workload.

If the time spent advancing non-removable transaction ID surpasses the
max_conflict_retention_duration threshold, the apply worker would stop
retaining information for conflict detection. The replication slot
pg_conflict_detection will be invalidated if all apply workers associated with
the subscription, where retain_conflict_info is enabled, confirm that the
retention duration exceeded the max_conflict_retention_duration.

In this patch, a replication slot will not be automatically re-created if it
becomes invalidated. Users can disable retain_conflict_info and re-enable it
after confirming that the replication slot has been dropped. An upcoming patch
will include support for automatic slot recreation once at least one apply
worker confirms that the retention duration is within the
max_conflict_retention_duration limit.

To monitor worker's conflict retention status, this patch also introduces a new
column 'retain_conflict_info' in the pg_stat_subscription view. This column
indicates whether the apply worker is effectively retaining conflict
information. The value is set to true only if retain_conflict_info is enabled
for the associated subscription, and the retention duration for conflict
detection by the apply worker has not exceeded max_conflict_retention_duration.
---
 doc/src/sgml/config.sgml                      |  41 ++++
 doc/src/sgml/monitoring.sgml                  |  13 ++
 doc/src/sgml/system-views.sgml                |  11 ++
 src/backend/catalog/system_views.sql          |   3 +-
 src/backend/replication/logical/launcher.c    |  80 +++++++-
 src/backend/replication/logical/worker.c      | 183 +++++++++++++++++-
 src/backend/replication/slot.c                |  13 ++
 src/backend/utils/misc/guc_tables.c           |  13 ++
 src/backend/utils/misc/postgresql.conf.sample |   1 +
 src/include/catalog/pg_proc.dat               |   6 +-
 src/include/replication/logicallauncher.h     |   1 +
 src/include/replication/slot.h                |   4 +-
 src/include/replication/worker_internal.h     |   6 +
 src/test/regress/expected/rules.out           |   5 +-
 14 files changed, 355 insertions(+), 25 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 88e2aa43ab0..ca4625f80bd 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5378,6 +5378,47 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-max-conflict-retention-duration" xreflabel="max_conflict_retention_duration">
+      <term><varname>max_conflict_retention_duration</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>max_conflict_retention_duration</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Maximum duration (in milliseconds) for which conflict
+        information can be retained for conflict detection by the apply worker.
+        The default value is <literal>0</literal>, indicating that conflict
+        information is retained until it is no longer needed for detection
+        purposes.
+       </para>
+       <para>
+        The replication slot
+        <quote><literal>pg_conflict_detection</literal></quote> that used to
+        retain conflict information will be invalidated if all apply workers
+        associated with the subscriptions, where
+        <literal>retain_conflict_info</literal> is enabled, confirm that the
+        retention duration exceeded the
+        <literal>max_conflict_retention_duration</literal>. If the replication
+        slot is invalidated, you can disable
+        <literal>retain_conflict_info</literal> and re-enable it after
+        confirming this replication slot has been dropped.
+       </para>
+       <para>
+        This option is effective only if a subscription with
+        <literal>retain_conflict_info</literal> enabled is present, and the
+        associated apply worker is active.
+       </para>
+       <warning>
+        <para>
+         Note that setting a non-zero value for this option could lead to
+         conflict information being removed prematurely, potentially missing
+         some conflict detections.
+        </para>
+       </warning>
+      </listitem>
+     </varlistentry>
+
      </variablelist>
     </sect2>
 
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index d768ea065c5..5a9f17beb23 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -2109,6 +2109,19 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        sender; NULL for parallel apply workers
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>retain_conflict_info</structfield> <type>boolean</type>
+      </para>
+      <para>
+       True if <link linkend="sql-createsubscription-params-with-retain-conflict-info"><literal>retain_conflict_info</literal></link>
+       is enabled and the duration for which conflict information is
+       retained for conflict detection by this apply worker does not exceed
+       <link linkend="guc-max-conflict-retention-duration"><literal>max_conflict_retention_duration</literal></link>; NULL for
+       parallel apply workers and table synchronization workers.
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/system-views.sgml b/doc/src/sgml/system-views.sgml
index b58c52ea50f..fe552a86fad 100644
--- a/doc/src/sgml/system-views.sgml
+++ b/doc/src/sgml/system-views.sgml
@@ -2936,6 +2936,17 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
           <xref linkend="guc-idle-replication-slot-timeout"/> duration.
          </para>
         </listitem>
+        <listitem>
+         <para>
+          <literal>conflict_retention_exceeds_max_duration</literal> means that
+          the duration for retaining conflict information, which is used
+          in logical replication conflict detection, has exceeded the maximum
+          allowable limit. It is set only for the slot
+          <literal>pg_conflict_detection</literal>, which is created when
+          <link linkend="sql-createsubscription-params-with-retain-conflict-info"><literal>retain_conflict_info</literal></link>
+          is enabled.
+         </para>
+        </listitem>
        </itemizedlist>
       </para></entry>
      </row>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 637a312e198..c4443249496 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -993,7 +993,8 @@ CREATE VIEW pg_stat_subscription AS
             st.last_msg_send_time,
             st.last_msg_receipt_time,
             st.latest_end_lsn,
-            st.latest_end_time
+            st.latest_end_time,
+            st.retain_conflict_info
     FROM pg_subscription su
             LEFT JOIN pg_stat_get_subscription(NULL) st
                       ON (st.subid = su.oid);
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 07d686c6d8c..f873a817192 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -23,6 +23,7 @@
 #include "access/tableam.h"
 #include "access/xact.h"
 #include "catalog/pg_subscription.h"
+#include "catalog/pg_subscription_d.h"
 #include "catalog/pg_subscription_rel.h"
 #include "funcapi.h"
 #include "lib/dshash.h"
@@ -43,6 +44,7 @@
 #include "utils/memutils.h"
 #include "utils/pg_lsn.h"
 #include "utils/snapmgr.h"
+#include "utils/syscache.h"
 
 /* max sleep time between cycles (3min) */
 #define DEFAULT_NAPTIME_PER_CYCLE 180000L
@@ -51,6 +53,7 @@
 int			max_logical_replication_workers = 4;
 int			max_sync_workers_per_subscription = 2;
 int			max_parallel_apply_workers_per_subscription = 2;
+int			max_conflict_retention_duration = 0;
 
 LogicalRepWorker *MyLogicalRepWorker = NULL;
 
@@ -446,6 +449,7 @@ retry:
 	worker->leader_pid = is_parallel_apply_worker ? MyProcPid : InvalidPid;
 	worker->parallel_apply = is_parallel_apply_worker;
 	worker->oldest_nonremovable_xid = InvalidFullTransactionId;
+	worker->stop_conflict_info_retention = false;
 	worker->last_lsn = InvalidXLogRecPtr;
 	TIMESTAMP_NOBEGIN(worker->last_send_time);
 	TIMESTAMP_NOBEGIN(worker->last_recv_time);
@@ -1157,7 +1161,8 @@ ApplyLauncherMain(Datum main_arg)
 		MemoryContext oldctx;
 		long		wait_time = DEFAULT_NAPTIME_PER_CYCLE;
 		bool		can_advance_xmin = true;
-		bool		retain_conflict_info = false;
+		int			nretain_conflict_info = 0;
+		int			nstop_retention = 0;
 		FullTransactionId xmin = InvalidFullTransactionId;
 
 		CHECK_FOR_INTERRUPTS();
@@ -1186,7 +1191,7 @@ ApplyLauncherMain(Datum main_arg)
 			 */
 			if (sub->retainconflictinfo)
 			{
-				retain_conflict_info = true;
+				nretain_conflict_info++;
 				can_advance_xmin &= sub->enabled;
 
 				/*
@@ -1212,22 +1217,32 @@ ApplyLauncherMain(Datum main_arg)
 				 * the new xmin for advancing the replication slot used in
 				 * conflict detection.
 				 */
-				if (sub->retainconflictinfo && can_advance_xmin)
+				if (sub->retainconflictinfo)
 				{
 					FullTransactionId nonremovable_xid;
+					bool		stop_conflict_info_retention;
 
 					SpinLockAcquire(&w->relmutex);
 					nonremovable_xid = w->oldest_nonremovable_xid;
+					stop_conflict_info_retention = w->stop_conflict_info_retention;
 					SpinLockRelease(&w->relmutex);
 
+					/*
+					 * Skip collecting oldest_nonremovable_xid for workers
+					 * that have stopped conflict retention.
+					 */
+					if (stop_conflict_info_retention)
+						nstop_retention++;
+
 					/*
 					 * Stop advancing xmin if an invalid non-removable
 					 * transaction ID is found, otherwise update xmin.
 					 */
-					if (!FullTransactionIdIsValid(nonremovable_xid))
+					else if (!FullTransactionIdIsValid(nonremovable_xid))
 						can_advance_xmin = false;
-					else if (!FullTransactionIdIsValid(xmin) ||
-							 FullTransactionIdPrecedes(nonremovable_xid, xmin))
+					else if (can_advance_xmin &&
+							 (!FullTransactionIdIsValid(xmin) ||
+							  FullTransactionIdPrecedes(nonremovable_xid, xmin)))
 						xmin = nonremovable_xid;
 				}
 
@@ -1272,11 +1287,34 @@ ApplyLauncherMain(Datum main_arg)
 			}
 		}
 
+		/*
+		 * Do nothing if the replication slot is invalidated due to conflict
+		 * retention duration.
+		 */
+		if (nretain_conflict_info &&
+			MyReplicationSlot->data.invalidated != RS_INVAL_NONE)
+		{
+			Assert(MyReplicationSlot->data.invalidated == RS_INVAL_CONFLICT_RETENTION_DURATION);
+		}
+
+		/*
+		 * Invalidate the conflict slot if all workers with
+		 * retain_conflict_info enabled have stopped further conflict
+		 * retention.
+		 */
+		else if (nstop_retention && nretain_conflict_info == nstop_retention)
+		{
+			ReplicationSlotRelease();
+			InvalidateObsoleteReplicationSlots(RS_INVAL_CONFLICT_RETENTION_DURATION,
+											   InvalidXLogRecPtr, InvalidOid,
+											   InvalidTransactionId);
+		}
+
 		/*
 		 * Maintain the xmin value of the replication slot for conflict
 		 * detection if needed.
 		 */
-		if (retain_conflict_info)
+		else if (nretain_conflict_info)
 		{
 			if (can_advance_xmin)
 				advance_conflict_slot_xmin(xmin);
@@ -1470,7 +1508,7 @@ GetLeaderApplyWorkerPid(pid_t pid)
 Datum
 pg_stat_get_subscription(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_COLS	10
+#define PG_STAT_GET_SUBSCRIPTION_COLS	11
 	Oid			subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
 	int			i;
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
@@ -1547,6 +1585,32 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 				elog(ERROR, "unknown worker type");
 		}
 
+		/*
+		 * Only the leader apply worker manages conflict retention (see
+		 * maybe_advance_nonremovable_xid() for details).
+		 */
+		if (!isParallelApplyWorker(&worker) && !isTablesyncWorker(&worker))
+		{
+			HeapTuple	tup;
+			Form_pg_subscription subform;
+
+			tup = SearchSysCache1(SUBSCRIPTIONOID,
+								  ObjectIdGetDatum(worker.subid));
+
+			if (!HeapTupleIsValid(tup))
+				elog(ERROR, "cache lookup failed for subscription %u",
+					 worker.subid);
+
+			subform = (Form_pg_subscription) GETSTRUCT(tup);
+
+			values[10] = subform->subretainconflictinfo &&
+				!worker.stop_conflict_info_retention;
+
+			ReleaseSysCache(tup);
+		}
+		else
+			nulls[10] = true;
+
 		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
 							 values, nulls);
 
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 6a59db47583..3e19b56ae22 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -173,6 +173,7 @@
 #include "replication/logicalrelation.h"
 #include "replication/logicalworker.h"
 #include "replication/origin.h"
+#include "replication/slot.h"
 #include "replication/walreceiver.h"
 #include "replication/worker_internal.h"
 #include "rewrite/rewriteHandler.h"
@@ -453,8 +454,11 @@ static void request_publisher_status(RetainConflictInfoData *rci_data);
 static void wait_for_publisher_status(RetainConflictInfoData *rci_data,
 									  bool status_received);
 static void wait_for_local_flush(RetainConflictInfoData *rci_data);
+static void reset_conflict_info_fields(RetainConflictInfoData *rci_data);
+static bool should_stop_conflict_info_retention(RetainConflictInfoData *rci_data);
 static void adjust_xid_advance_interval(RetainConflictInfoData *rci_data,
 										bool new_xid_found);
+static void update_conflict_retention_status(void);
 
 static void apply_handle_commit_internal(LogicalRepCommitData *commit_data);
 static void apply_handle_insert_internal(ApplyExecutionData *edata,
@@ -3865,7 +3869,8 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
 		 * Ensure to wake up when it's possible to attempt to advance the
 		 * non-removable transaction ID.
 		 */
-		if (data.phase == RCI_GET_CANDIDATE_XID && data.xid_advance_interval)
+		if (!MyLogicalRepWorker->stop_conflict_info_retention &&
+			data.phase == RCI_GET_CANDIDATE_XID && data.xid_advance_interval)
 			wait_time = Min(wait_time, data.xid_advance_interval);
 
 		rc = WaitLatchOrSocket(MyLatch,
@@ -4138,6 +4143,10 @@ can_advance_nonremovable_xid(RetainConflictInfoData *rci_data)
 	if (!MySubscription->retainconflictinfo)
 		return false;
 
+	/* No need to advance if we have already stopped retaining */
+	if (MyLogicalRepWorker->stop_conflict_info_retention)
+		return false;
+
 	return true;
 }
 
@@ -4283,6 +4292,13 @@ wait_for_publisher_status(RetainConflictInfoData *rci_data,
 	if (!status_received)
 		return;
 
+	/*
+	 * Stop retaining conflict information if required (See
+	 * should_stop_conflict_info_retention() for details).
+	 */
+	if (should_stop_conflict_info_retention(rci_data))
+		return;
+
 	if (!FullTransactionIdIsValid(rci_data->last_phase_at))
 		rci_data->last_phase_at = rci_data->remote_nextxid;
 
@@ -4364,6 +4380,25 @@ wait_for_local_flush(RetainConflictInfoData *rci_data)
 	 * have a WAL position greater than the rci_data->remote_lsn.
 	 */
 	if (!AllTablesyncsReady())
+	{
+		/*
+		 * Reset the timer to prevent stopping conflict info retention due to
+		 * time consumed during table synchronization. Given that table sync
+		 * is an infrequent operation, it merits a time adjustment.
+		 */
+		if (max_conflict_retention_duration)
+			rci_data->candidate_xid_time = rci_data->last_recv_time
+				? rci_data->last_recv_time
+				: GetCurrentTimestamp();
+
+		return;
+	}
+
+	/*
+	 * Stop retaining conflict information if required (See
+	 * should_stop_conflict_info_retention() for details).
+	 */
+	if (should_stop_conflict_info_retention(rci_data))
 		return;
 
 	/*
@@ -4389,7 +4424,10 @@ wait_for_local_flush(RetainConflictInfoData *rci_data)
 		rci_data->flushpos_update_time = rci_data->last_recv_time;
 	}
 
-	/* Return to wait for the changes to be applied */
+	/*
+	 * Return if changes up to the remote_lsn have not been applied and
+	 * flushed.
+	 */
 	if (last_flushpos < rci_data->remote_lsn)
 		return;
 
@@ -4409,12 +4447,21 @@ wait_for_local_flush(RetainConflictInfoData *rci_data)
 	/* Notify launcher to update the xmin of the conflict slot */
 	ApplyLauncherWakeup();
 
-	/*
-	 * Reset all data fields except those used to determine the timing for the
-	 * next round of transaction ID advancement. We can even use
-	 * flushpos_update_time in the next round to decide whether to get the
-	 * latest flush position.
-	 */
+	reset_conflict_info_fields(rci_data);
+
+	/* process the next phase */
+	process_rci_phase_transition(rci_data, false);
+}
+
+/*
+ * Reset all data fields of RetainConflictInfoData except those used to
+ * determine the timing for the next round of transaction ID advancement. We
+ * can even use flushpos_update_time in the next round to decide whether to get
+ * the latest flush position.
+ */
+static void
+reset_conflict_info_fields(RetainConflictInfoData *rci_data)
+{
 	rci_data->phase = RCI_GET_CANDIDATE_XID;
 	rci_data->remote_lsn = InvalidXLogRecPtr;
 	rci_data->remote_oldestxid = InvalidFullTransactionId;
@@ -4422,9 +4469,64 @@ wait_for_local_flush(RetainConflictInfoData *rci_data)
 	rci_data->reply_time = 0;
 	rci_data->last_phase_at = InvalidFullTransactionId;
 	rci_data->candidate_xid = InvalidFullTransactionId;
+}
 
-	/* process the next phase */
-	process_rci_phase_transition(rci_data, false);
+/*
+ * Check whether conflict information retention should be stopped because the
+ * wait time has exceeded the maximum limit (max_conflict_retention_duration).
+ *
+ * If retention should be stopped, set
+ * LogicalRepWorker->stop_conflict_info_retention to true, notify the launcher to
+ * invalidate the slot, and return true. Return false otherwise.
+ *
+ * Currently, the retention will not resume automatically unless user manually
+ * disables retain_conflict_info and re-enables it after confirming that the
+ * replication slot has been dropped.
+ */
+static bool
+should_stop_conflict_info_retention(RetainConflictInfoData *rci_data)
+{
+	TimestampTz now;
+
+	Assert(FullTransactionIdIsValid(rci_data->candidate_xid));
+	Assert(rci_data->phase == RCI_WAIT_FOR_PUBLISHER_STATUS ||
+		   rci_data->phase == RCI_WAIT_FOR_LOCAL_FLUSH);
+
+	if (!max_conflict_retention_duration)
+		return false;
+
+	/*
+	 * Use last_recv_time when applying changes in the loop to avoid
+	 * unnecessary system time retrieval. If last_recv_time is not available,
+	 * obtain the current timestamp.
+	 */
+	now = rci_data->last_recv_time ? rci_data->last_recv_time : GetCurrentTimestamp();
+
+	/*
+	 * Return if the wait time has not exceeded the maximum limit
+	 * (max_conflict_retention_duration).
+	 */
+	if (!TimestampDifferenceExceeds(rci_data->candidate_xid_time, now,
+									max_conflict_retention_duration))
+		return false;
+
+	ereport(LOG,
+			errmsg("logical replication worker for subscription \"%s\" will stop retaining conflict information",
+				   MySubscription->name),
+			errdetail("The time spent advancing the non-removable transaction ID has exceeded the maximum limit of %u ms.",
+					  max_conflict_retention_duration));
+
+	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
+	MyLogicalRepWorker->oldest_nonremovable_xid = InvalidFullTransactionId;
+	MyLogicalRepWorker->stop_conflict_info_retention = true;
+	SpinLockRelease(&MyLogicalRepWorker->relmutex);
+
+	/* Notify launcher to invalidate the conflict slot */
+	ApplyLauncherWakeup();
+
+	reset_conflict_info_fields(rci_data);
+
+	return true;
 }
 
 /*
@@ -4457,6 +4559,10 @@ adjust_xid_advance_interval(RetainConflictInfoData *rci_data, bool new_xid_found
 		 */
 		rci_data->xid_advance_interval = Min(rci_data->xid_advance_interval * 2,
 											 max_interval);
+
+		/* Ensure the wait time remains within the maximum limit */
+		rci_data->xid_advance_interval = Min(rci_data->xid_advance_interval,
+											 max_conflict_retention_duration);
 	}
 	else
 	{
@@ -4468,6 +4574,51 @@ adjust_xid_advance_interval(RetainConflictInfoData *rci_data, bool new_xid_found
 	}
 }
 
+/*
+ * Update the conflict retention status for the current apply worker. It checks
+ * whether the worker should stop retaining conflict information due to
+ * invalidation of the replication slot ("pg_conflict_detection").
+ *
+ * Currently, the replication slot is invalidated only if the duration for
+ * retaining conflict information exceeds the allowed maximum.
+ */
+static void
+update_conflict_retention_status(void)
+{
+	ReplicationSlotInvalidationCause cause = RS_INVAL_NONE;
+	ReplicationSlot *slot;
+
+	/* Exit early if retaining conflict information is not required */
+	if (!MySubscription->retainconflictinfo)
+		return;
+
+	/*
+	 * Only the leader apply worker manages conflict retention (see
+	 * maybe_advance_nonremovable_xid() for details).
+	 */
+	if (!am_leader_apply_worker())
+		return;
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
+	slot = SearchNamedReplicationSlot(CONFLICT_DETECTION_SLOT, false);
+
+	if (slot)
+	{
+		SpinLockAcquire(&slot->mutex);
+		cause = slot->data.invalidated;
+		SpinLockRelease(&slot->mutex);
+
+		Assert(cause == RS_INVAL_NONE || cause == RS_INVAL_CONFLICT_RETENTION_DURATION);
+	}
+
+	LWLockRelease(ReplicationSlotControlLock);
+
+	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
+	MyLogicalRepWorker->stop_conflict_info_retention = cause != RS_INVAL_NONE;
+	SpinLockRelease(&MyLogicalRepWorker->relmutex);
+}
+
 /*
  * Exit routine for apply workers due to subscription parameter changes.
  */
@@ -4639,6 +4790,16 @@ maybe_reread_subscription(void)
 		CommitTransactionCommand();
 
 	MySubscriptionValid = true;
+
+	/*
+	 * Update worker status to avoid unnecessary conflict retention if the
+	 * replication slot ("pg_conflict_detection") was invalidated prior to
+	 * enabling the retain_conflict_info option. This is also necessary to
+	 * restart conflict retention if the user has disabled and subsequently
+	 * re-enabled the retain_conflict_info option, resulting in the
+	 * replication slot being recreated.
+	 */
+	update_conflict_retention_status();
 }
 
 /*
@@ -5285,6 +5446,8 @@ InitializeLogRepWorker(void)
 						MySubscription->name)));
 
 	CommitTransactionCommand();
+
+	update_conflict_retention_status();
 }
 
 /*
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 668279cb4e8..bce4af1bdcd 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -116,6 +116,7 @@ static const SlotInvalidationCauseMap SlotInvalidationCauses[] = {
 	{RS_INVAL_HORIZON, "rows_removed"},
 	{RS_INVAL_WAL_LEVEL, "wal_level_insufficient"},
 	{RS_INVAL_IDLE_TIMEOUT, "idle_timeout"},
+	{RS_INVAL_CONFLICT_RETENTION_DURATION, "conflict_retention_exceeds_max_duration"},
 };
 
 /*
@@ -1610,6 +1611,11 @@ ReportSlotInvalidation(ReplicationSlotInvalidationCause cause,
 								 "idle_replication_slot_timeout");
 				break;
 			}
+		case RS_INVAL_CONFLICT_RETENTION_DURATION:
+			appendStringInfo(&err_detail,
+							 _("The duration for retaining conflict information exceeds the configured \"%s\" limit of %d milliseconds"),
+							 "max_conflict_retention_duration", max_conflict_retention_duration);
+			break;
 		case RS_INVAL_NONE:
 			pg_unreachable();
 	}
@@ -1728,6 +1734,12 @@ DetermineSlotInvalidationCause(uint32 possible_causes, ReplicationSlot *s,
 		}
 	}
 
+	if (possible_causes & RS_INVAL_CONFLICT_RETENTION_DURATION)
+	{
+		if (IsReservedSlotName(NameStr(s->data.name)))
+			return RS_INVAL_CONFLICT_RETENTION_DURATION;
+	}
+
 	return RS_INVAL_NONE;
 }
 
@@ -1995,6 +2007,7 @@ InvalidatePossiblyObsoleteSlot(uint32 possible_causes,
  * - RS_INVAL_WAL_LEVEL: is logical and wal_level is insufficient
  * - RS_INVAL_IDLE_TIMEOUT: has been idle longer than the configured
  *   "idle_replication_slot_timeout" duration.
+ * - RS_INVAL_CONFLICT_RETENTION_DURATION: is "pg_conflict_detection"
  *
  * Note: This function attempts to invalidate the slot for multiple possible
  * causes in a single pass, minimizing redundant iterations. The "cause"
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 2f8cbd86759..e8249ba8491 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -3388,6 +3388,19 @@ struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"max_conflict_retention_duration",
+			PGC_SIGHUP,
+			REPLICATION_SUBSCRIBERS,
+			gettext_noop("Maximum duration for retaining information used in logical replication conflict detection."),
+			NULL,
+			GUC_UNIT_MS
+		},
+		&max_conflict_retention_duration,
+		0, 0, INT_MAX,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Sets the amount of time to wait before forcing "
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 34826d01380..4cabb0e7c48 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -400,6 +400,7 @@
 					# (change requires restart)
 #max_sync_workers_per_subscription = 2	# taken from max_logical_replication_workers
 #max_parallel_apply_workers_per_subscription = 2	# taken from max_logical_replication_workers
+#max_conflict_retention_duration = 0	# in milliseconds; 0 disables
 
 
 #------------------------------------------------------------------------------
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 62beb71da28..2e7a337762f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5695,9 +5695,9 @@
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', proparallel => 'r',
   prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,oid,int4,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz,text}',
-  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{subid,subid,relid,pid,leader_pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,worker_type}',
+  proallargtypes => '{oid,oid,oid,int4,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz,text,bool}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,relid,pid,leader_pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,worker_type,retain_conflict_info}',
   prosrc => 'pg_stat_get_subscription' },
 { oid => '2026', descr => 'statistics: current backend PID',
   proname => 'pg_backend_pid', provolatile => 's', proparallel => 'r',
diff --git a/src/include/replication/logicallauncher.h b/src/include/replication/logicallauncher.h
index 7b29f1814db..d347d3d67f6 100644
--- a/src/include/replication/logicallauncher.h
+++ b/src/include/replication/logicallauncher.h
@@ -15,6 +15,7 @@
 extern PGDLLIMPORT int max_logical_replication_workers;
 extern PGDLLIMPORT int max_sync_workers_per_subscription;
 extern PGDLLIMPORT int max_parallel_apply_workers_per_subscription;
+extern PGDLLIMPORT int max_conflict_retention_duration;
 
 extern void ApplyLauncherRegister(void);
 extern void ApplyLauncherMain(Datum main_arg);
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index e03e123a2ff..a8d0844e9cf 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -66,10 +66,12 @@ typedef enum ReplicationSlotInvalidationCause
 	RS_INVAL_WAL_LEVEL = (1 << 2),
 	/* idle slot timeout has occurred */
 	RS_INVAL_IDLE_TIMEOUT = (1 << 3),
+	/* duration of conflict info retention exceeds the maximum limit */
+	RS_INVAL_CONFLICT_RETENTION_DURATION = (1 << 4),
 } ReplicationSlotInvalidationCause;
 
 /* Maximum number of invalidation causes */
-#define	RS_INVAL_MAX_CAUSES 4
+#define	RS_INVAL_MAX_CAUSES 5
 
 /*
  * On-Disk data of a replication slot, preserved across restarts.
diff --git a/src/include/replication/worker_internal.h b/src/include/replication/worker_internal.h
index c70359d9935..41dc2a2e07c 100644
--- a/src/include/replication/worker_internal.h
+++ b/src/include/replication/worker_internal.h
@@ -121,6 +121,12 @@ typedef struct LogicalRepWorker
 	 */
 	FullTransactionId oldest_nonremovable_xid;
 
+	/*
+	 * Indicates whether the apply worker has stopped retaining conflict
+	 * information. This is used only when retain_conflict_info is enabled.
+	 */
+	bool		stop_conflict_info_retention;
+
 	/* Stats. */
 	XLogRecPtr	last_lsn;
 	TimestampTz last_send_time;
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 6cf828ca8d0..79ed5233edb 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2165,9 +2165,10 @@ pg_stat_subscription| SELECT su.oid AS subid,
     st.last_msg_send_time,
     st.last_msg_receipt_time,
     st.latest_end_lsn,
-    st.latest_end_time
+    st.latest_end_time,
+    st.retain_conflict_info
    FROM (pg_subscription su
-     LEFT JOIN pg_stat_get_subscription(NULL::oid) st(subid, relid, pid, leader_pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time, worker_type) ON ((st.subid = su.oid)));
+     LEFT JOIN pg_stat_get_subscription(NULL::oid) st(subid, relid, pid, leader_pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time, worker_type, retain_conflict_info) ON ((st.subid = su.oid)));
 pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
-- 
2.31.1

