Re: [HACKERS] Block level parallel vacuum

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От Mahendra Singh
Тема Re: [HACKERS] Block level parallel vacuum
Дата
Msg-id CAKYtNAoMnWM6RBz1gocaP0=MQdwkcOujETtuh=_k+imqCuxLjA@mail.gmail.com
обсуждение исходный текст
Ответ на Re: [HACKERS] Block level parallel vacuum  (Amit Kapila <amit.kapila16@gmail.com>)
Ответы Re: [HACKERS] Block level parallel vacuum
Список pgsql-hackers
Дерево обсуждения
On Wed, 27 Nov 2019 at 08:14, Amit Kapila <amit.kapila16@gmail.com> wrote:
On Wed, Nov 27, 2019 at 12:52 AM Masahiko Sawada
<masahiko.sawada@2ndquadrant.com> wrote:
>
>
> I've incorporated the comments I got so far including the above and
> the memory alignment issue.
>

Thanks, I will look into the new version.  BTW, why haven't you posted
0001 patch (IndexAM API's patch)?  I think without that we need to use
the previous version for that. Also, I think we should post Dilip's
patch related to Gist index [1] modifications for parallel vacuum or
at least have a mention for that while posting a new version as
without that even make check fails.

[1] - https://www.postgresql.org/message-id/CAFiTN-uQY%2BB%2BCLb8W3YYdb7XmB9hyYFXkAy3C7RY%3D-YSWRV1DA%40mail.gmail.com


I did some testing on the top of v33 patch set. By debugging, I was able to hit one assert in lazy_parallel_vacuum_or_cleanup_indexes.
TRAP: FailedAssertion("nprocessed == nindexes_remains", File: "vacuumlazy.c", Line: 2099)

I further debugged and found that this assert is not valid in all the cases. Here, nprocessed can be less than nindexes_remains in some cases because it is  possible that parallel worker is launched for vacuum and idx count is incremented in vacuum_or_cleanup_indexes_worker for particular index  but work is still not finished(lvshared->nprocessed is not incremented yet) so in that case, nprocessed will be less than nindexes_remains.  I think, we should remove this assert.

I have one comment for assert used variable:

+#ifdef USE_ASSERT_CHECKING
+ int nprocessed = 0;
+#endif

I think, we can make above declaration as " int nprocessed PG_USED_FOR_ASSERTS_ONLY = 0" so that code looks good because this USE_ASSERT_CHECKING is used in 3 places in 20-30 code lines.

Thanks and Regards
Mahendra Thalor

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