Horton

Re: Connections hang indefinitely while taking a gin index's LWLock buffer_content lock

Alexander Korotkov <aekorotkov@gmail.com>

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From: Alexander Korotkov <aekorotkov@gmail.com>
To: Andrey Borodin <x4mmm@yandex-team.ru>
Cc: Peter Geoghegan <pg@bowt.ie>, Andres Freund <andres@anarazel.de>, chenhj <chjischj@163.com>, Teodor Sigaev <teodor@sigaev.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-12-13T12:03:54Z
Lists: pgsql-hackers 
On Wed, Dec 12, 2018 at 4:08 PM Andrey Borodin <x4mmm@yandex-team.ru> wrote:
> > 12 дек. 2018 г., в 3:26, Alexander Korotkov <aekorotkov@gmail.com> написал(а):
> >
> > BTW, I still can't see you're setting deleteXid field of
> > ginxlogDeletePage struct anywhere.
> Oops. Fixed.
> >
> > Also, I note that protection against re-usage of recently deleted
> > pages is implemented differently than it is in B-tree.
> > 1) You check TransactionIdPrecedes(GinPageGetDeleteXid(page),
> > RecentGlobalDataXmin)), while B-tree checks
> > TransactionIdPrecedes(opaque->btpo.xact, RecentGlobalXmin).  Could you
> > clarify why do we use RecentGlobalDataXmin instead of RecentGlobalXmin
> > here?
> As far as I understand RecentGlobalDataXmin may be slightly farther than RecentGlobalXmin in case when replication_slot_catalog_xmin is holding RecentGlobalXmin. And GIN is never used by catalog tables. But let's use RecentGlobalXmin like in B-tree.
>
> > 2) B-tree checks this condition both before putting page into FSM and
> > after getting page from FSM.  You're checking only after getting page
> > from FSM.  Approach of B-tree looks better for me.  It's seems more
> > consistent when FSM pages are really free for usage.
> Fixed.

Thank you.  I've revised your patch and pushed it.  As long as two
other patches in this thread.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Commits

  1. Fix WAL format incompatibility introduced by backpatching of 52ac6cd2d0

  2. Fix wrong backpatching of ginRedoDeletePage() deadlock fix

  3. Fix deadlock in GIN vacuum introduced by 218f51584d5

  4. Prevent GIN deleted pages from being reclaimed too early

  5. Prevent deadlock in ginRedoDeletePage()

  6. Reduce page locking in GIN vacuum

  7. Fix race condition in GIN posting tree page deletion.