changes_amit_v54_0001.patch

diff --git a/src/backend/replication/logical/applyparallelworker.c b/src/backend/replication/logical/applyparallelworker.c
index f9dda6daee..7c2b0e0b5e 100644
--- a/src/backend/replication/logical/applyparallelworker.c
+++ b/src/backend/replication/logical/applyparallelworker.c
@@ -64,12 +64,13 @@
  * etc.) of the publisher and subscriber could be different, applying
  * transactions in parallel mode on the subscriber side can cause some
  * deadlocks that do not occur on the publisher side which is expected and can
- * happen even without parallel mode. In order to detect the deadlocks among
- * leader and parallel apply workers, we need to ensure that we wait using lmgr
- * locks, otherwise, such deadlocks won't be detected. The other approach was
- * to not allow parallelism when the schema of tables is different between the
- * publisher and subscriber but that would be too restrictive and would require
- * the publisher to send much more information than it is currently sending.
+ * happen even without parallel mode when there are concurrent operations on
+ * the subscriber. In order to detect the deadlocks among leader and parallel
+ * apply workers, we need to ensure that we wait using lmgr locks, otherwise,
+ * such deadlocks won't be detected. The other approach was to not allow
+ * parallelism when the schema of tables is different between the publisher
+ * and subscriber but that would be too restrictive and would require the
+ * publisher to send much more information than it is currently sending.
  *
  * Consider a case where the subscribed table does not have a unique key on the
  * publisher and has a unique key on the subscriber.
@@ -1308,6 +1309,10 @@ pa_start_subtrans(TransactionId current_xid, TransactionId top_xid)
 void
 pa_clean_subtrans(void)
 {
+	/*
+	 * We don't need to free this explicitly as the allocated memory will be
+	 * freed at the transaction end.
+	 */
 	subxactlist = NIL;
 }
 
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 997a1ef2d3..9510dc5683 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -484,6 +484,7 @@ should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
 		return MyLogicalRepWorker->relid == rel->localreloid;
 	else if (am_parallel_apply_worker())
 	{
+		/* We don't synchronize rel's that are in unknown state. */
 		if (rel->state != SUBREL_STATE_READY &&
 			rel->state != SUBREL_STATE_UNKNOWN)
 			ereport(ERROR,
@@ -1945,6 +1946,7 @@ apply_handle_stream_commit(StringInfo s)
 			pa_wait_for_xact_finish(winfo);
 
 			store_flush_position(commit_data.end_lsn, winfo->shared->last_commit_end);
+
 			(void) pa_free_worker(winfo, xid);
 
 			pgstat_report_stat(false);
diff --git a/src/include/replication/worker_internal.h b/src/include/replication/worker_internal.h
index 9b2ca9461b..c10b503e76 100644
--- a/src/include/replication/worker_internal.h
+++ b/src/include/replication/worker_internal.h
@@ -124,7 +124,10 @@ typedef struct ParallelApplyWorkerShared
 	 */
 	pg_atomic_uint32 pending_stream_count;
 
-	/* XactLastCommitEnd from the parallel apply worker. */
+	/*
+	 * XactLastCommitEnd from the parallel apply worker. This is required to
+	 * update the lsn_mappings by leader worker.
+	 */
 	XLogRecPtr	last_commit_end;
 } ParallelApplyWorkerShared;