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

Gurjeet Singh <singh(dot)gurjeet(at)gmail(dot)com> writes:
> On Mon, Jan 14, 2013 at 10:33 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I think this is unacceptable on its face. It essentially supposes that
>> relcache entries are reliable storage. They are not.

> Would it be acceptable if we inverted the meaning of the struct member, and
> named it to rd_rows_not_inserted. When registering an ON COMMIT action, we
> can set this member to true, and set it to false when inserting a row into
> it. The pre-commit hook will truncate any relation that doesn't have this
> member set to true.

> With that in place, even if the relcache entry is discarded midway through
> the transaction, the cleanup code will truncate the relation, preserving
> the correct behaviour.

Well, that would fail in the safe direction, but it just seems
excessively ugly and hard-to-understand. Given the field demand for
this optimization (which so far as I've noticed is nil), I'm not
convinced we need to do this.

regards, tom lane