get_relid_attribute_name is dead, long live get_attname

The modern way is to use a missing_ok argument instead of two separate
almost-identical routines, so do that.

Author: Michaël Paquier
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/20180201063212.GE6398@paquier.xyz

1 files changed, 8 insertions, 23 deletions

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index e8aa179347d..51b6b4f7bbe 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -765,19 +765,19 @@ get_opfamily_proc(Oid opfamily, Oid lefttype, Oid righttype, int16 procnum)
 
 /*
  * get_attname
- *		Given the relation id and the attribute number,
- *		return the "attname" field from the attribute relation.
+ *		Given the relation id and the attribute number, return the "attname"
+ *		field from the attribute relation as a palloc'ed string.
  *
- * Note: returns a palloc'd copy of the string, or NULL if no such attribute.
+ * If no such attribute exists and missing_ok is true, NULL is returned;
+ * otherwise a not-intended-for-user-consumption error is thrown.
  */
 char *
-get_attname(Oid relid, AttrNumber attnum)
+get_attname(Oid relid, AttrNumber attnum, bool missing_ok)
 {
 	HeapTuple	tp;
 
 	tp = SearchSysCache2(ATTNUM,
-						 ObjectIdGetDatum(relid),
-						 Int16GetDatum(attnum));
+						 ObjectIdGetDatum(relid), Int16GetDatum(attnum));
 	if (HeapTupleIsValid(tp))
 	{
 		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
@@ -787,26 +787,11 @@ get_attname(Oid relid, AttrNumber attnum)
 		ReleaseSysCache(tp);
 		return result;
 	}
-	else
-		return NULL;
-}
-
-/*
- * get_relid_attribute_name
- *
- * Same as above routine get_attname(), except that error
- * is handled by elog() instead of returning NULL.
- */
-char *
-get_relid_attribute_name(Oid relid, AttrNumber attnum)
-{
-	char	   *attname;
 
-	attname = get_attname(relid, attnum);
-	if (attname == NULL)
+	if (!missing_ok)
 		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
 			 attnum, relid);
-	return attname;
+	return NULL;
 }
 
 /*