From: Greg Smith <greg@2ndquadrant.com>
To: Tobias Brox <tobixen@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: locking issue on simple selects?
Date: Wed, 15 Sep 2010 15:28:24 -0400
Message-ID: <4C911E58.6030605@2ndquadrant.com> (raw)
In-Reply-To: <AANLkTikzssP3AKeQhM+tB_8tScRGs2iGSqTJJUg2w3DP@mail.gmail.com>
References: <AANLkTikh++7mouBb7cr2C9zMPKtRffVxDK0QFTf16HLo@mail.gmail.com>
<4096.1284557987@sss.pgh.pa.us>
<AANLkTikzssP3AKeQhM+tB_8tScRGs2iGSqTJJUg2w3DP@mail.gmail.com>
Tobias Brox wrote:
> I thought so, we have a logging script that logs the content of
> the pg_locks table, it didn't log anything interesting but it may be a
> problem with the script itself. It does an inner join on
> pg_locks.relation = pg_class.oid but when I check now this join seems
> to remove most of the rows in the pg_locks table.
Some of the waits you might be running into will be things waiting on
another transaction holding a lock to finish, which are probably wiped
out by this approach. There are some useful examples of lock views on
the wiki:
http://wiki.postgresql.org/wiki/Lock_Monitoringhttp://wiki.postgresql.org/wiki/Lock_dependency_informationhttp://wiki.postgresql.org/wiki/Find_Locks
And the idea you have of coverting the pg_class one to an outer join
will help.
The other thing you should try is toggling on log_lock_waits and
possibly reducing deadlock_timeout. This will put a lot of the
information you're trying to collect right into the logs.
--
Greg Smith, 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us
Author, "PostgreSQL 9.0 High Performance" Pre-ordering at:
https://www.packtpub.com/postgresql-9-0-high-performance/book
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To: pgsql-performance@postgresql.org
Cc: greg@2ndquadrant.com, tobixen@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: locking issue on simple selects?
In-Reply-To: <4C911E58.6030605@2ndquadrant.com>
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