Remove ineffective check against dropped columns from slot_getattr().

anarazel · anarazel · commit c670d0faace6 · 2018-11-09T17:40:40.000-08:00
Before this commit slot_getattr() checked for dropped columns (returning NULL in that case), but only after checking for previously deformed columns. As slot_deform_tuple() does not contain such a check, the check in slot_getattr() would often not have been reached, depending on previous use of the slot. These days locking and plan invalidation ought to ensure that dropped columns are not accessed in query plans. Therefore this commit just drops the insufficient check in slot_getattr(). It's possible that we'll find some holes againt use of dropped columns, but if so, those need to be addressed independent of slot_getattr(), as most accesses don't go through that function anyway. Author: Andres Freund Discussion: https://postgr.es/m/20181107174403.zai7fedgcjoqx44p@alap3.anarazel.de
diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c
@@ -1132,17 +1132,6 @@ slot_getattr(TupleTableSlot *slot, int attnum, bool *isnull)
 		return (Datum) 0;
 	}
 
-	/*
-	 * If the attribute's column has been dropped, we force a NULL result.
-	 * This case should not happen in normal use, but it could happen if we
-	 * are executing a plan cached before the column was dropped.
-	 */
-	if (TupleDescAttr(tupleDesc, attnum - 1)->attisdropped)
-	{
-		*isnull = true;
-		return (Datum) 0;
-	}
-
 	/*
 	 * Extract the attribute, along with any preceding attributes.
 	 */
