Subject: Re: Extension Enhancement: Buffer Invalidation in pg_buffercache

From: jian he <[email-masked]>
Date: Tue, 4 Jul 2023 19:53:39 +0800

On Tue, Jul 4, 2023 at 5:45 PM Japin Li <[email-masked]> wrote:

>
> On Tue, 04 Jul 2023 at 17:00, jian he <[email-masked]> wrote:
> > the following will also crash. no idea why.
> > begin;
> >     select count(*) from onek;
> >     select relpages from pg_class where relname = 'onek'; --queryA
> >
> >     SELECT count(*) FROM pg_buffercache WHERE relfilenode =
> > pg_relation_filenode('onek'::regclass); --queryB
> >
> >     insert into onek values(default);
> >
> >     select count(pg_buffercache_invalidate(bufferid)) from
> >     pg_buffercache where relfilenode =
> > pg_relation_filenode('onek'::regclass);
> >
> > ---------------------------------
> > queryA returns 35, queryB returns 37.
> > ----------------------------------
> > crash info:
> > test_dev=*#     insert into onek values(default);
> > INSERT 0 1
> > test_dev=*#     select count(pg_buffercache_invalidate(bufferid)) from
> >     pg_buffercache where relfilenode =
> > pg_relation_filenode('onek'::regclass);
> > TRAP: failed Assert("resarr->nitems < resarr->maxitems"), File:
> >
> "../../Desktop/pg_sources/main/postgres/src/backend/utils/resowner/resowner.c",
> > Line: 275, PID: 1533312
>
> According to the comments of ResourceArrayAdd(), the caller must have
> previously
> done ResourceArrayEnlarge(). I tried to call ResourceOwnerEnlargeBuffers()
> before
> PinBuffer_Locked(), so it can avoid this crash.
>
>                 if ((buf_state & BM_DIRTY) == BM_DIRTY)
>                 {
> +                       /* make sure we can handle the pin */
> +                       ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
> +
>                         /*
>                          * Try once to flush the dirty buffer.
>                          */
>                         PinBuffer_Locked(bufHdr);
>
> --
> Regrads,
> Japin Li.
>

thanks. tested flush pg_catalog, public schema, now, both works as pitched.