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 <mats.kindahl@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/4379aac8-26f1-42f2-a356-ff0e886228d3@gmail.com

2 files changed, 17 insertions, 16 deletions

diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 456b267f70b..06b52c65300 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/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);
 	}
 
 	/*
diff --git a/contrib/tcn/tcn.c b/contrib/tcn/tcn.c
index 3158dee0f26..9ca47f17cac 100644
--- a/contrib/tcn/tcn.c
+++ b/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;