Re: Patches for TODO item: Avoid truncating empty OCDR temp tables on COMMIT

On 15.01.2013 21:03, Tom Lane wrote:
> Robert Haas<robertmhaas@gmail.com>  writes:
>> On the third hand, the fact that a table is OCDR is recorded in
>> backend-local storage somewhere, and that storage (unlike the
>> relcache) had better be reliable.  So maybe there's some way to
>> finesse it that way.
>
> Hm, keep a flag in that storage you mean?  Yeah, that could possibly
> work.

Sounds reasonable.

Until someone gets around to write a patch along those lines, I'm 
inclined to apply this one liner:

*** a/src/backend/commands/tablecmds.c
--- b/src/backend/commands/tablecmds.c
***************
*** 10124,10130 **** PreCommit_on_commit_actions(void)
   				/* Do nothing (there shouldn't be such entries, actually) */
   				break;
   			case ONCOMMIT_DELETE_ROWS:
! 				oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
   				break;
   			case ONCOMMIT_DROP:
   				{
--- 10124,10136 ----
   				/* Do nothing (there shouldn't be such entries, actually) */
   				break;
   			case ONCOMMIT_DELETE_ROWS:
! 				/*
! 				 * If this transaction hasn't accessed any temporary relations,
! 				 * we can skip truncating ON COMMIT DELETE ROWS tables, as
! 				 * they must still be empty.
! 				 */
! 				if (MyXactAccessedTempRel)
! 					oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
   				break;
   			case ONCOMMIT_DROP:
   				{

We already have that MyXactAccessedTempRel global flag. Just checking 
that should cover many common cases.

- Heikki