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: 2018-12-11T22:26:37Z
Lists: pgsql-hackers 
On Tue, Dec 11, 2018 at 10:14 AM Andrey Borodin <x4mmm@yandex-team.ru> wrote:
> > 11 дек. 2018 г., в 3:43, Alexander Korotkov <aekorotkov@gmail.com> написал(а):
> >
> > Attached patch appears to be incomplete.  GinPageSetDeleteXid() is
> > called only in ginRedoDeletePage(), so only in recovery, while it
> > should be set during normal work too.  deleteXid field of
> > ginxlogDeletePage is never set.
>
> Sorry, I've messed it again. Forgot to include ginvacuum.c changes. Here it is.

BTW, I still can't see you're setting deleteXid field of
ginxlogDeletePage struct anywhere.

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?
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.

------
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.