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BUG #5946: Long exclusive lock taken by vacuum (not full)

From: "Maxim Boguk" <Maxim(dot)Boguk(at)gmail(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: BUG #5946: Long exclusive lock taken by vacuum (not full)
Date: 2011-03-25 08:56:41
Message-ID: 201103250856.p2P8ufGc004544@wwwmaster.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-bugs
The following bug has been logged online:

Bug reference:      5946
Logged by:          Maxim Boguk
Email address:      Maxim(dot)Boguk(at)gmail(dot)com
PostgreSQL version: 8.4
Operating system:   Linux
Description:        Long exclusive lock taken by vacuum (not full)
Details: 

From documentation I know that vacuum (without full) can truncate empty
pages from end of a relation if they are free and vacuum successfully grabed
exclusive lock for short time.

However, I wasn't ready to learn that 'short exclusive lock' can be 10-20
minutes in some cases.

In my case vacuum tried to truncate last 10-15GB from 100Gb relation, and
each time (3) it was cost 10+ minutes of service downtime (because that
table was completely locked).

Is  that correct behaviour? Are here any way to speedup that process or at
least allow read-only queries during that time?

PS: no exessive disk IO observed during that 10+ min locks.

Responses

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Next:From: Raman SharmaDate: 2011-03-25 09:47:14
Subject: BUG #5947: Error while running query
Previous:From: shenwenguangDate: 2011-03-25 08:26:09
Subject: BUG #5945: serial repetition Error!

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