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Re: pending patch: Re: HS/SR and smart shutdown

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: pending patch: Re: HS/SR and smart shutdown
Date: 2010-03-31 15:16:21
Message-ID: n2n603c8f071003310816zd23e9515nbefe9cc8dc36967d@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Mar 31, 2010 at 5:02 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> > >From what I have seen, the comment about PM_WAIT_BACKENDS is incorrect.
>> > "backends might be waiting for the WAL record that conflicts with their
>> > queries to be replayed". Recovery sometimes waits for backends, but
>> > backends never wait for recovery.
>>
>> Really? As Heikki explained before, backends might wait for the lock
>> taken by the startup process.
>> http://archives.postgresql.org/pgsql-hackers/2010-01/msg02984.php
>
> Backends wait for locks, yes, but they could be waiting for user locks
> also. That is not "waiting for the WAL record", that concept does not
> exist.

Hmm... this is a good point, on two levels.  First, the comment is not
as well-phrased as it could be.  Second, I wonder why we can't kill
the startup process and WAL receiver right away, and then wait for the
backends to die off afterwards.

...Robert

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