Add TupleDescGetDefault()

This unifies some repetitive code.

Note: I didn't push the "not found" error message into the new
function, even though all existing callers would be able to make use
of it.  Using the existing error handling as-is would probably require
exposing the Relation type via tupdesc.h, which doesn't seem
desirable.  (Or even if we changed it to just report the OID, it would
inject the concept of a relation containing the tuple descriptor into
tupdesc.h, which might be a layering violation.  Perhaps some further
improvements could be considered here separately.)

Discussion: https://www.postgresql.org/message-id/flat/52a125e4-ff9a-95f5-9f61-b87cf447e4da%40eisentraut.org

1 files changed, 1 insertions, 15 deletions

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index b486ab559a8..41a362310a8 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -1246,21 +1246,7 @@ build_column_default(Relation rel, int attrno)
 	 */
 	if (att_tup->atthasdef)
 	{
-		if (rd_att->constr && rd_att->constr->num_defval > 0)
-		{
-			AttrDefault *defval = rd_att->constr->defval;
-			int			ndef = rd_att->constr->num_defval;
-
-			while (--ndef >= 0)
-			{
-				if (attrno == defval[ndef].adnum)
-				{
-					/* Found it, convert string representation to node tree. */
-					expr = stringToNode(defval[ndef].adbin);
-					break;
-				}
-			}
-		}
+		expr = TupleDescGetDefault(rd_att, attrno);
 		if (expr == NULL)
 			elog(ERROR, "default expression not found for attribute %d of relation \"%s\"",
 				 attrno, RelationGetRelationName(rel));