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Re: Question about ALTER TABLE DROP CONSTRAINT on 9.1 -- psql crashes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Craig Ringer <ringerc(at)ringerc(dot)id(dot)au>
Cc: Greg Williamson <gwilliamson39(at)yahoo(dot)com>, "pgsql-admin(at)postgresql(dot)org" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Question about ALTER TABLE DROP CONSTRAINT on 9.1 -- psql crashes
Date: 2012-08-10 04:20:48
Message-ID: 13011.1344572448@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-admin
Craig Ringer <ringerc(at)ringerc(dot)id(dot)au> writes:
> On 08/10/2012 10:06 AM, Tom Lane wrote:
>> That sure sounds like the source of your problem.  It might be sane if
>> it killed only processes that *had been idle* for at least three
>> seconds, but I'm not sure there is any easy way to determine that ...

> wouldn't:

> select * from pg_stat_activity
> where current_query = '<IDLE> in transaction'
> AND query_start < current_timestamp - INTERVAL '3 seconds';

> do it?

No, that would find sessions that were idle and whose last command
started at least 3 seconds ago.  But it might have completed only
microseconds ago.  The symptoms Greg is describing are consistent
with this kill script running during a short interval between his
index-build command and his COMMIT.

As of 9.2 there's a "state_change" timestamp column in pg_stat_activity
that would provide a safer check, but it's not in existing releases ...

			regards, tom lane

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Subject: Re: Question about ALTER TABLE DROP CONSTRAINT on 9.1 -- psql crashes
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