Re: generic plans and "initial" pruning

On Fri, Apr 8, 2022 at 8:45 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> Most looked fine changes to me except a couple of typos, so I've
> adopted those into the attached new version, even though I know it's
> too late to try to apply it.
>
> + * XXX is it worth doing a bms_copy() on glob->minLockRelids if
> + * glob->containsInitialPruning is true?. I'm slighly worried that the
> + * Bitmapset could have a very long empty tail resulting in excessive
> + * looping during AcquireExecutorLocks().
> + */
>
> I guess I trust your instincts about bitmapset operation efficiency
> and what you've written here makes sense. It's typical for leaf
> partitions to have been appended toward the tail end of rtable and I'd
> imagine their indexes would be in the tail words of minLockRelids. If
> copying the bitmapset removes those useless words, I don't see why we
> shouldn't do that. So added:
>
> + /*
> + * It seems worth doing a bms_copy() on glob->minLockRelids if we deleted
> + * bit from it just above to prevent empty tail bits resulting in
> + * inefficient looping during AcquireExecutorLocks().
> + */
> + if (glob->containsInitialPruning)
> + glob->minLockRelids = bms_copy(glob->minLockRelids)
>
> Not 100% about the comment I wrote.

And the quoted code change missed a semicolon in the v14 that I
hurriedly sent on Friday. (Had apparently forgotten to `git add` the
hunk to fix that).

Sending v15 that fixes that to keep the cfbot green for now.

--
Amit Langote
EDB: http://www.enterprisedb.com