From: Craig James <craig_james@emolecules.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Deadlock on "select ... for update"?
Date: Wed, 30 Nov 2011 10:08:42 -0800
Message-ID: <4ED6712A.8040603@emolecules.com> (raw)
In-Reply-To: <CAOR=d=1Dr8mzoXXr93-ev4pQqK=SsD=eJeHPkDzjTddfg6DTqQ@mail.gmail.com>
References: <CACKquuGP-S1xXw4cYr-5VhzkqEC3w9bOkhnXEwqoWKXD3EkU=w@mail.gmail.com>
<CAOR=d=1Dr8mzoXXr93-ev4pQqK=SsD=eJeHPkDzjTddfg6DTqQ@mail.gmail.com>
On 11/29/11 10:36 AM, Scott Marlowe wrote:
> On Tue, Nov 29, 2011 at 11:15 AM, Craig James
> <craig_james@emolecules.com> wrote:
>> Several times recently one of our databases has gotten stuck with the
>> following situation:
>>
>> postgres=# select datname, procpid, usename, current_query from
>> pg_stat_activity where current_query != '<IDLE>';
>> datname | procpid | usename |
>> current_query
>> ------------+---------+----------+--------------------------------------------------------------------------------------------------------
>> emolecules | 13503 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid<= 0 for update
>> emolecules | 32082 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid<= 0 for update
>> emolecules | 17974 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid<= 0 for update
>> emolecules | 31299 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>> emolecules | 30247 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>> postgres | 1705 | postgres | select datname, procpid, usename,
>> current_query from pg_stat_activity where current_query != '<IDLE>';
>> emolecules | 28866 | customerdb |<IDLE> in transaction
>> emolecules | 21394 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>> emolecules | 22237 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>> (9 rows)
>>
>> It's obvious that they're all waiting ... but for what? The "<IDLE>"
>> process looks like the culprit, but how do I figure out what it's doing?
>> The next time this happens, what queries can I run to help diagnose what's
>> going on?
>> This is PG 8.4.4 on Ubuntu 10.
> Does this help?
>
> http://wiki.postgresql.org/wiki/Lock_Monitoring
Yes, thanks! That's exactly what I needed.
Craig
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To: pgsql-admin@postgresql.org
Cc: craig_james@emolecules.com, scott.marlowe@gmail.com
Subject: Re: Deadlock on "select ... for update"?
In-Reply-To: <4ED6712A.8040603@emolecules.com>
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