Remove make_temptable_name_n().

This small function is only used in one place, and it fails to
handle quoted table names (although the table name portion of the
input should never be quoted in current usage).  In addition to
removing make_temptable_name_n() in favor of open-coding it where
needed, this commit ensures the "diff" table name is properly
quoted in order to future-proof this area a bit.

Author: Aleksander Alekseev <aleksander@tigerdata.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Shinya Kato <shinya11.kato@gmail.com>
Discussion: https://postgr.es/m/CAJ7c6TO3a5q2NKRsjdJ6sLf8isVe4aMaaX1-Hj2TdHdhFw8zRA%40mail.gmail.com

src/backend/commands/matview.c

@@ -61,7 +61,6 @@ static void transientrel_shutdown(DestReceiver *self);
 static void transientrel_destroy(DestReceiver *self);
 static uint64 refresh_matview_datafill(DestReceiver *dest, Query *query,
 									   const char *queryString, bool is_create);
-static char *make_temptable_name_n(char *tempname, int n);
 static void refresh_by_match_merge(Oid matviewOid, Oid tempOid, Oid relowner,
 								   int save_sec_context);
 static void refresh_by_heap_swap(Oid matviewOid, Oid OIDNewHeap, char relpersistence);
@@ -556,28 +555,6 @@ transientrel_destroy(DestReceiver *self)
 	pfree(self);
 }
 
-
-/*
- * Given a qualified temporary table name, append an underscore followed by
- * the given integer, to make a new table name based on the old one.
- * The result is a palloc'd string.
- *
- * As coded, this would fail to make a valid SQL name if the given name were,
- * say, "FOO"."BAR".  Currently, the table name portion of the input will
- * never be double-quoted because it's of the form "pg_temp_NNN", cf
- * make_new_heap().  But we might have to work harder someday.
- */
-static char *
-make_temptable_name_n(char *tempname, int n)
-{
-	StringInfoData namebuf;
-
-	initStringInfo(&namebuf);
-	appendStringInfoString(&namebuf, tempname);
-	appendStringInfo(&namebuf, "_%d", n);
-	return namebuf.data;
-}
-
 /*
  * refresh_by_match_merge
  *
@@ -620,6 +597,9 @@ refresh_by_match_merge(Oid matviewOid, Oid tempOid, Oid relowner,
 	char	   *matviewname;
 	char	   *tempname;
 	char	   *diffname;
+	char	   *temprelname;
+	char	   *diffrelname;
+	char	   *nsp;
 	TupleDesc	tupdesc;
 	bool		foundUniqueIndex;
 	List	   *indexoidlist;
@@ -632,9 +612,17 @@ refresh_by_match_merge(Oid matviewOid, Oid tempOid, Oid relowner,
 	matviewname = quote_qualified_identifier(get_namespace_name(RelationGetNamespace(matviewRel)),
 											 RelationGetRelationName(matviewRel));
 	tempRel = table_open(tempOid, NoLock);
-	tempname = quote_qualified_identifier(get_namespace_name(RelationGetNamespace(tempRel)),
+
-										  RelationGetRelationName(tempRel));
+	/*
-	diffname = make_temptable_name_n(tempname, 2);
+	 * Build qualified names of the temporary table and the diff table.  The
+	 * only difference between them is the "_2" suffix on the diff table name.
+	 */
+	nsp = get_namespace_name(RelationGetNamespace(tempRel));
+	temprelname = RelationGetRelationName(tempRel);
+	diffrelname = psprintf("%s_2", temprelname);
+
+	tempname = quote_qualified_identifier(nsp, temprelname);
+	diffname = quote_qualified_identifier(nsp, diffrelname);
 
 	relnatts = RelationGetNumberOfAttributes(matviewRel);