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Re: Finding if old transactions are running...

From: jtv(at)xs4all(dot)nl
To: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au>,"Christopher Browne" <cbbrowne(at)acm(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Finding if old transactions are running...
Date: 2005-02-25 06:22:23
Message-ID: 25376.202.47.227.16.1109312543.squirrel@202.47.227.16 (view raw or flat)
Thread:
Lists: pgsql-hackers
Bruce Momjian wrote:

>> > You can get that from pg_stat_activity, if you have the relevant stats
>> > turned on.
>>
>> pg_stat_activity will tell you about the oldest active query, but not
>> about oldest open transaction.
>
> And pg_stat_activity can lose information when the network is under
> heavy load too.

On a side note, a similar issue came up with libpqxx, in the part that
deals with connections being lost while committing a transaction.  The
library tries to reconnect and figure out whether the commit completed or
not, but it was pointed out that the commit might actually still be in
progress by that time.

Tom, I believe you said at the time that I should check pg_stat_activity. 
My current code polls it for the old backend pid.  But if that is neither
100% reliable nor unconditionally available, wouldn't it be better if I
just queried pg_locks for the transaction's ID?  Would that work for all
backend versions I can expect to see?


Jeroen



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