Use stack allocated StringInfoDatas, where possible

Various places that were using StringInfo but didn'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.  This also simplifies the cleanup,
in a few cases.

Author: Mats Kindahl <[email protected]>
Reviewed-by: David Rowley <[email protected]>
Reviewed-by: Chao Li <[email protected]>
Discussion: https://postgr.es/m/[email protected]

Author: david-rowley

contrib/postgres_fdw/postgres_fdw.c

@@ -2841,7 +2841,7 @@ postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
 	 */
 	if (list_length(fdw_private) > FdwScanPrivateRelations)
 	{
-		StringInfo	relations;
+		StringInfoData relations;
 		char	   *rawrelations;
 		char	   *ptr;
 		int			minrti,
@@ -2875,7 +2875,7 @@ postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
 		rtoffset = bms_next_member(plan->fs_base_relids, -1) - minrti;
 
 		/* Now we can translate the string */
-		relations = makeStringInfo();
+		initStringInfo(&relations);
 		ptr = rawrelations;
 		while (*ptr)
 		{
@@ -2897,24 +2897,24 @@ postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
 					char	   *namespace;
 
 					namespace = get_namespace_name_or_temp(get_rel_namespace(rte->relid));
-					appendStringInfo(relations, "%s.%s",
+					appendStringInfo(&relations, "%s.%s",
 									 quote_identifier(namespace),
 									 quote_identifier(relname));
 				}
 				else
-					appendStringInfoString(relations,
+					appendStringInfoString(&relations,
 										   quote_identifier(relname));
 				refname = (char *) list_nth(es->rtable_names, rti - 1);
 				if (refname == NULL)
 					refname = rte->eref->aliasname;
 				if (strcmp(refname, relname) != 0)
-					appendStringInfo(relations, " %s",
+					appendStringInfo(&relations, " %s",
 									 quote_identifier(refname));
 			}
 			else
-				appendStringInfoChar(relations, *ptr++);
+				appendStringInfoChar(&relations, *ptr++);
 		}
-		ExplainPropertyText("Relations", relations->data, es);
+		ExplainPropertyText("Relations", relations.data, es);
 	}
 
 	/*

contrib/tcn/tcn.c

@@ -66,12 +66,13 @@ triggered_change_notification(PG_FUNCTION_ARGS)
 	TupleDesc	tupdesc;
 	char	   *channel;
 	char		operation;
-	StringInfo	payload = makeStringInfo();
+	StringInfoData payload;
 	bool		foundPK;
 
 	List	   *indexoidlist;
 	ListCell   *indexoidscan;
 
+	initStringInfo(&payload);
 	/* make sure it's called as a trigger */
 	if (!CALLED_AS_TRIGGER(fcinfo))
 		ereport(ERROR,
@@ -149,22 +150,22 @@ triggered_change_notification(PG_FUNCTION_ARGS)
 
 				foundPK = true;
 
-				strcpy_quoted(payload, RelationGetRelationName(rel), '"');
-				appendStringInfoCharMacro(payload, ',');
-				appendStringInfoCharMacro(payload, operation);
+				strcpy_quoted(&payload, RelationGetRelationName(rel), '"');
+				appendStringInfoCharMacro(&payload, ',');
+				appendStringInfoCharMacro(&payload, operation);
 
 				for (i = 0; i < indnkeyatts; i++)
 				{
 					int			colno = index->indkey.values[i];
 					Form_pg_attribute attr = TupleDescAttr(tupdesc, colno - 1);
 
-					appendStringInfoCharMacro(payload, ',');
-					strcpy_quoted(payload, NameStr(attr->attname), '"');
-					appendStringInfoCharMacro(payload, '=');
-					strcpy_quoted(payload, SPI_getvalue(trigtuple, tupdesc, colno), '\'');
+					appendStringInfoCharMacro(&payload, ',');
+					strcpy_quoted(&payload, NameStr(attr->attname), '"');
+					appendStringInfoCharMacro(&payload, '=');
+					strcpy_quoted(&payload, SPI_getvalue(trigtuple, tupdesc, colno), '\'');
 				}
 
-				Async_Notify(channel, payload->data);
+				Async_Notify(channel, payload.data);
 			}
 			ReleaseSysCache(indexTuple);
 			break;

src/backend/access/transam/xlogbackup.c

@@ -31,18 +31,19 @@ build_backup_content(BackupState *state, bool ishistoryfile)
 	char		startstrbuf[128];
 	char		startxlogfile[MAXFNAMELEN]; /* backup start WAL file */
 	XLogSegNo	startsegno;
-	StringInfo	result = makeStringInfo();
-	char	   *data;
+	StringInfoData result;
 
 	Assert(state != NULL);
 
+	initStringInfo(&result);
+
 	/* Use the log timezone here, not the session timezone */
 	pg_strftime(startstrbuf, sizeof(startstrbuf), "%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&state->starttime, log_timezone));
 
 	XLByteToSeg(state->startpoint, startsegno, wal_segment_size);
 	XLogFileName(startxlogfile, state->starttli, startsegno, wal_segment_size);
-	appendStringInfo(result, "START WAL LOCATION: %X/%08X (file %s)\n",
+	appendStringInfo(&result, "START WAL LOCATION: %X/%08X (file %s)\n",
 					 LSN_FORMAT_ARGS(state->startpoint), startxlogfile);
 
 	if (ishistoryfile)
@@ -52,18 +53,18 @@ build_backup_content(BackupState *state, bool ishistoryfile)
 
 		XLByteToSeg(state->stoppoint, stopsegno, wal_segment_size);
 		XLogFileName(stopxlogfile, state->stoptli, stopsegno, wal_segment_size);
-		appendStringInfo(result, "STOP WAL LOCATION: %X/%08X (file %s)\n",
+		appendStringInfo(&result, "STOP WAL LOCATION: %X/%08X (file %s)\n",
 						 LSN_FORMAT_ARGS(state->stoppoint), stopxlogfile);
 	}
 
-	appendStringInfo(result, "CHECKPOINT LOCATION: %X/%08X\n",
+	appendStringInfo(&result, "CHECKPOINT LOCATION: %X/%08X\n",
 					 LSN_FORMAT_ARGS(state->checkpointloc));
-	appendStringInfoString(result, "BACKUP METHOD: streamed\n");
-	appendStringInfo(result, "BACKUP FROM: %s\n",
+	appendStringInfoString(&result, "BACKUP METHOD: streamed\n");
+	appendStringInfo(&result, "BACKUP FROM: %s\n",
 					 state->started_in_recovery ? "standby" : "primary");
-	appendStringInfo(result, "START TIME: %s\n", startstrbuf);
-	appendStringInfo(result, "LABEL: %s\n", state->name);
-	appendStringInfo(result, "START TIMELINE: %u\n", state->starttli);
+	appendStringInfo(&result, "START TIME: %s\n", startstrbuf);
+	appendStringInfo(&result, "LABEL: %s\n", state->name);
+	appendStringInfo(&result, "START TIMELINE: %u\n", state->starttli);
 
 	if (ishistoryfile)
 	{
@@ -73,22 +74,19 @@ build_backup_content(BackupState *state, bool ishistoryfile)
 		pg_strftime(stopstrfbuf, sizeof(stopstrfbuf), "%Y-%m-%d %H:%M:%S %Z",
 					pg_localtime(&state->stoptime, log_timezone));
 
-		appendStringInfo(result, "STOP TIME: %s\n", stopstrfbuf);
-		appendStringInfo(result, "STOP TIMELINE: %u\n", state->stoptli);
+		appendStringInfo(&result, "STOP TIME: %s\n", stopstrfbuf);
+		appendStringInfo(&result, "STOP TIMELINE: %u\n", state->stoptli);
 	}
 
 	/* either both istartpoint and istarttli should be set, or neither */
 	Assert(XLogRecPtrIsInvalid(state->istartpoint) == (state->istarttli == 0));
 	if (!XLogRecPtrIsInvalid(state->istartpoint))
 	{
-		appendStringInfo(result, "INCREMENTAL FROM LSN: %X/%08X\n",
+		appendStringInfo(&result, "INCREMENTAL FROM LSN: %X/%08X\n",
 						 LSN_FORMAT_ARGS(state->istartpoint));
-		appendStringInfo(result, "INCREMENTAL FROM TLI: %u\n",
+		appendStringInfo(&result, "INCREMENTAL FROM TLI: %u\n",
 						 state->istarttli);
 	}
 
-	data = result->data;
-	pfree(result);
-
-	return data;
+	return result.data;
 }

src/backend/backup/basebackup.c

@@ -239,7 +239,7 @@ perform_base_backup(basebackup_options *opt, bbsink *sink,
 	TimeLineID	endtli;
 	backup_manifest_info manifest;
 	BackupState *backup_state;
-	StringInfo	tablespace_map;
+	StringInfoData tablespace_map;
 
 	/* Initial backup state, insofar as we know it now. */
 	state.tablespaces = NIL;
@@ -263,11 +263,11 @@ perform_base_backup(basebackup_options *opt, bbsink *sink,
 
 	/* Allocate backup related variables. */
 	backup_state = (BackupState *) palloc0(sizeof(BackupState));
-	tablespace_map = makeStringInfo();
+	initStringInfo(&tablespace_map);
 
 	basebackup_progress_wait_checkpoint();
 	do_pg_backup_start(opt->label, opt->fastcheckpoint, &state.tablespaces,
-					   backup_state, tablespace_map);
+					   backup_state, &tablespace_map);
 
 	state.startptr = backup_state->startpoint;
 	state.starttli = backup_state->starttli;
@@ -342,7 +342,7 @@ perform_base_backup(basebackup_options *opt, bbsink *sink,
 				if (opt->sendtblspcmapfile)
 				{
 					sendFileWithContent(sink, TABLESPACE_MAP,
-										tablespace_map->data, -1, &manifest);
+										tablespace_map.data, -1, &manifest);
 					sendtblspclinks = false;
 				}
 
@@ -399,7 +399,7 @@ perform_base_backup(basebackup_options *opt, bbsink *sink,
 		endtli = backup_state->stoptli;
 
 		/* Deallocate backup-related variables. */
-		destroyStringInfo(tablespace_map);
+		pfree(tablespace_map.data);
 		pfree(backup_state);
 	}
 	PG_END_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));

src/backend/commands/subscriptioncmds.c

@@ -491,20 +491,20 @@ static void
 check_publications(WalReceiverConn *wrconn, List *publications)
 {
 	WalRcvExecResult *res;
-	StringInfo	cmd;
+	StringInfoData cmd;
 	TupleTableSlot *slot;
 	List	   *publicationsCopy = NIL;
 	Oid			tableRow[1] = {TEXTOID};
 
-	cmd = makeStringInfo();
-	appendStringInfoString(cmd, "SELECT t.pubname FROM\n"
+	initStringInfo(&cmd);
+	appendStringInfoString(&cmd, "SELECT t.pubname FROM\n"
 						   " pg_catalog.pg_publication t WHERE\n"
 						   " t.pubname IN (");
-	GetPublicationsStr(publications, cmd, true);
-	appendStringInfoChar(cmd, ')');
+	GetPublicationsStr(publications, &cmd, true);
+	appendStringInfoChar(&cmd, ')');
 
-	res = walrcv_exec(wrconn, cmd->data, 1, tableRow);
-	destroyStringInfo(cmd);
+	res = walrcv_exec(wrconn, cmd.data, 1, tableRow);
+	pfree(cmd.data);
 
 	if (res->status != WALRCV_OK_TUPLES)
 		ereport(ERROR,
@@ -535,15 +535,17 @@ check_publications(WalReceiverConn *wrconn, List *publications)
 	if (list_length(publicationsCopy))
 	{
 		/* Prepare the list of non-existent publication(s) for error message. */
-		StringInfo	pubnames = makeStringInfo();
+		StringInfoData pubnames;
+
+		initStringInfo(&pubnames);
 
-		GetPublicationsStr(publicationsCopy, pubnames, false);
+		GetPublicationsStr(publicationsCopy, &pubnames, false);
 		ereport(WARNING,
 				errcode(ERRCODE_UNDEFINED_OBJECT),
 				errmsg_plural("publication %s does not exist on the publisher",
 							  "publications %s do not exist on the publisher",
 							  list_length(publicationsCopy),
-							  pubnames->data));
+							  pubnames.data));
 	}
 }
 
@@ -2885,12 +2887,13 @@ fetch_relation_list(WalReceiverConn *wrconn, List *publications)
 	int			server_version = walrcv_server_version(wrconn);
 	bool		check_columnlist = (server_version >= 150000);
 	int			column_count = check_columnlist ? 4 : 3;
-	StringInfo	pub_names = makeStringInfo();
+	StringInfoData pub_names;
 
 	initStringInfo(&cmd);
+	initStringInfo(&pub_names);
 
 	/* Build the pub_names comma-separated string. */
-	GetPublicationsStr(publications, pub_names, true);
+	GetPublicationsStr(publications, &pub_names, true);
 
 	/* Get the list of relations from the publisher */
 	if (server_version >= 160000)
@@ -2917,7 +2920,7 @@ fetch_relation_list(WalReceiverConn *wrconn, List *publications)
 						 "                FROM pg_publication\n"
 						 "                WHERE pubname IN ( %s )) AS gpt\n"
 						 "             ON gpt.relid = c.oid\n",
-						 pub_names->data);
+						 pub_names.data);
 
 		/* From version 19, inclusion of sequences in the target is supported */
 		if (server_version >= 190000)
@@ -2926,7 +2929,7 @@ fetch_relation_list(WalReceiverConn *wrconn, List *publications)
 							 "  SELECT DISTINCT s.schemaname, s.sequencename, " CppAsString2(RELKIND_SEQUENCE) "::\"char\" AS relkind, NULL::int2vector AS attrs\n"
 							 "  FROM pg_catalog.pg_publication_sequences s\n"
 							 "  WHERE s.pubname IN ( %s )",
-							 pub_names->data);
+							 pub_names.data);
 	}
 	else
 	{
@@ -2939,10 +2942,10 @@ fetch_relation_list(WalReceiverConn *wrconn, List *publications)
 
 		appendStringInfo(&cmd, "FROM pg_catalog.pg_publication_tables t\n"
 						 " WHERE t.pubname IN ( %s )",
-						 pub_names->data);
+						 pub_names.data);
 	}
 
-	destroyStringInfo(pub_names);
+	pfree(pub_names.data);
 
 	res = walrcv_exec(wrconn, cmd.data, column_count, tableRow);
 	pfree(cmd.data);