Subject: [PATCH v1] Use stack allocated StringInfoDatas, where possible

From: Bertrand Drouvot <[email-masked]>
Date: Sun, 12 Apr 2026 10:09:22 +0000

Commit 6d0eba66275 already did most of the changes but missed the opportunities
in sequencesync.c.

Indeed, 5509055d6956 added a few cases that are using StringInfo but don't need
that StringInfo to exist beyond the scope of the function were using makeStringInfo(),
which allocates both a StringInfoData and the buffer it uses as two separate
allocations. It's more efficient for these cases to use a StringInfoData on the
stack and initialize it with initStringInfo(), which only allocates the string
buffer.

The reason 6d0eba66275 missed those is that 5509055d6956 has been committed
between the patch proposal for 6d0eba66275 and 6d0eba66275.

Author: Bertrand Drouvot <[email-masked]>
---
 .../replication/logical/sequencesync.c        | 39 ++++++++++---------
 1 file changed, 21 insertions(+), 18 deletions(-)
 100.0% src/backend/replication/logical/

diff --git a/src/backend/replication/logical/sequencesync.c b/src/backend/replication/logical/sequencesync.c
index a4fb6783ba9..ec7e76abf93 100644
--- a/src/backend/replication/logical/sequencesync.c
+++ b/src/backend/replication/logical/sequencesync.c
@@ -174,45 +174,45 @@ static void
 report_sequence_errors(List *mismatched_seqs_idx, List *insuffperm_seqs_idx,
 					   List *missing_seqs_idx)
 {
-	StringInfo	seqstr;
+	StringInfoData seqstr;
 
 	/* Quick exit if there are no errors to report */
 	if (!mismatched_seqs_idx && !insuffperm_seqs_idx && !missing_seqs_idx)
 		return;
 
-	seqstr = makeStringInfo();
+	initStringInfo(&seqstr);
 
 	if (mismatched_seqs_idx)
 	{
-		get_sequences_string(mismatched_seqs_idx, seqstr);
+		get_sequences_string(mismatched_seqs_idx, &seqstr);
 		ereport(WARNING,
 				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				errmsg_plural("mismatched or renamed sequence on subscriber (%s)",
 							  "mismatched or renamed sequences on subscriber (%s)",
 							  list_length(mismatched_seqs_idx),
-							  seqstr->data));
+							  seqstr.data));
 	}
 
 	if (insuffperm_seqs_idx)
 	{
-		get_sequences_string(insuffperm_seqs_idx, seqstr);
+		get_sequences_string(insuffperm_seqs_idx, &seqstr);
 		ereport(WARNING,
 				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				errmsg_plural("insufficient privileges on sequence (%s)",
 							  "insufficient privileges on sequences (%s)",
 							  list_length(insuffperm_seqs_idx),
-							  seqstr->data));
+							  seqstr.data));
 	}
 
 	if (missing_seqs_idx)
 	{
-		get_sequences_string(missing_seqs_idx, seqstr);
+		get_sequences_string(missing_seqs_idx, &seqstr);
 		ereport(WARNING,
 				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				errmsg_plural("missing sequence on publisher (%s)",
 							  "missing sequences on publisher (%s)",
 							  list_length(missing_seqs_idx),
-							  seqstr->data));
+							  seqstr.data));
 	}
 
 	ereport(ERROR,
@@ -388,10 +388,13 @@ copy_sequences(WalReceiverConn *conn)
 	List	   *mismatched_seqs_idx = NIL;
 	List	   *missing_seqs_idx = NIL;
 	List	   *insuffperm_seqs_idx = NIL;
-	StringInfo	seqstr = makeStringInfo();
-	StringInfo	cmd = makeStringInfo();
+	StringInfoData seqstr;
+	StringInfoData cmd;
 	MemoryContext oldctx;
 
+	initStringInfo(&seqstr);
+	initStringInfo(&cmd);
+
 #define MAX_SEQUENCES_SYNC_PER_BATCH 100
 
 	elog(DEBUG1,
@@ -423,13 +426,13 @@ copy_sequences(WalReceiverConn *conn)
 			LogicalRepSequenceInfo *seqinfo =
 				(LogicalRepSequenceInfo *) list_nth(seqinfos, idx);
 
-			if (seqstr->len > 0)
-				appendStringInfoString(seqstr, ", ");
+			if (seqstr.len > 0)
+				appendStringInfoString(&seqstr, ", ");
 
 			nspname_literal = quote_literal_cstr(seqinfo->nspname);
 			seqname_literal = quote_literal_cstr(seqinfo->seqname);
 
-			appendStringInfo(seqstr, "(%s, %s, %d)",
+			appendStringInfo(&seqstr, "(%s, %s, %d)",
 							 nspname_literal, seqname_literal, idx);
 
 			if (++batch_size == MAX_SEQUENCES_SYNC_PER_BATCH)
@@ -468,7 +471,7 @@ copy_sequences(WalReceiverConn *conn)
 		 * corresponding local entries without relying on result order or name
 		 * matching.
 		 */
-		appendStringInfo(cmd,
+		appendStringInfo(&cmd,
 						 "SELECT s.seqidx, ps.*, seq.seqtypid,\n"
 						 "       seq.seqstart, seq.seqincrement, seq.seqmin,\n"
 						 "       seq.seqmax, seq.seqcycle\n"
@@ -477,9 +480,9 @@ copy_sequences(WalReceiverConn *conn)
 						 "JOIN pg_class c ON c.relnamespace = n.oid AND c.relname = s.seqname\n"
 						 "JOIN pg_sequence seq ON seq.seqrelid = c.oid\n"
 						 "JOIN LATERAL pg_get_sequence_data(seq.seqrelid) AS ps ON true\n",
-						 seqstr->data);
+						 seqstr.data);
 
-		res = walrcv_exec(conn, cmd->data, lengthof(seqRow), seqRow);
+		res = walrcv_exec(conn, cmd.data, lengthof(seqRow), seqRow);
 		if (res->status != WALRCV_OK_TUPLES)
 			ereport(ERROR,
 					errcode(ERRCODE_CONNECTION_FAILURE),
@@ -567,8 +570,8 @@ copy_sequences(WalReceiverConn *conn)
 
 		ExecDropSingleTupleTableSlot(slot);
 		walrcv_clear_result(res);
-		resetStringInfo(seqstr);
-		resetStringInfo(cmd);
+		resetStringInfo(&seqstr);
+		resetStringInfo(&cmd);
 
 		batch_missing_count = batch_size - (batch_succeeded_count +
 											batch_mismatched_count +
-- 
2.34.1

--wggHK0nYArblB/da--