Optimize StringJoin() for when prefix-postfix is needed

Before this commit, we required multiple copies of the
same stringInfo if we needed to append/prepend data to
the stringInfo. Now, we optionally get prefix/postfix.

For large string operations, this can save up to %10
memory.

src/backend/distributed/utils/listutils.c

@@ -161,13 +161,31 @@ GeneratePositiveIntSequenceList(int upTo)
 /*
  * StringJoin gets a list of char * and then simply
  * returns a newly allocated char * joined with the
- * given delimiter.
+ * given delimiter. It uses ';' as the delimiter by
+ * default.
  */
 char *
 StringJoin(List *stringList, char delimiter)
+{
+	return StringJoinParams(stringList, delimiter, NULL, NULL);
+}
+
+
+/*
+ * StringJoin gets a list of char * and then simply
+ * returns a newly allocated char * joined with the
+ * given delimiter, prefix and postfix.
+ */
+char *
+StringJoinParams(List *stringList, char delimiter, char *prefix, char *postfix)
 {
 	StringInfo joinedString = makeStringInfo();
 
+	if (prefix != NULL)
+	{
+		appendStringInfoString(joinedString, prefix);
+	}
+
 	const char *command = NULL;
 	int curIndex = 0;
 	foreach_ptr(command, stringList)
@@ -180,6 +198,11 @@ StringJoin(List *stringList, char delimiter)
 		curIndex++;
 	}
 
+	if (postfix != NULL)
+	{
+		appendStringInfoString(joinedString, postfix);
+	}
+
 	return joinedString->data;
 }
 

src/backend/distributed/utils/multi_partitioning_utils.c

@@ -569,13 +569,11 @@ CreateFixPartitionShardIndexNames(Oid parentRelationId, Oid partitionRelationId,
 			task->taskId = taskId++;
 			task->taskType = DDL_TASK;
 
+			char *prefix = "SELECT pg_catalog.citus_run_local_command($$";
+			char *postfix = "$$)";
+			char *string = StringJoinParams(queryStringList, ';', prefix, postfix);
 
-			char *string = StringJoin(queryStringList, ';');
-			StringInfo commandToRun = makeStringInfo();
-
-			appendStringInfo(commandToRun,
-							 "SELECT pg_catalog.citus_run_local_command($$%s$$)", string);
-			SetTaskQueryString(task, commandToRun->data);
+			SetTaskQueryString(task, string);
 
 
 			task->dependentTaskList = NULL;

src/include/distributed/listutils.h

@@ -166,6 +166,8 @@ extern List * SortList(List *pointerList,
 extern void ** PointerArrayFromList(List *pointerList);
 extern HTAB * ListToHashSet(List *pointerList, Size keySize, bool isStringList);
 extern char * StringJoin(List *stringList, char delimiter);
+extern char * StringJoinParams(List *stringList, char delimiter,
+							   char *prefix, char *postfix);
 extern List * ListTake(List *pointerList, int size);
 extern void * safe_list_nth(const List *list, int index);
 extern List * GeneratePositiveIntSequenceList(int upTo);