Re: Extension Enhancement: Buffer Invalidation in pg_buffercache

On Tue, 04 Jul 2023 at 17:00, jian he <jian(dot)universality(at)gmail(dot)com> 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.