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Re: Anyone seen this kind of lock pileup?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Anyone seen this kind of lock pileup?
Date: 2010-11-17 23:56:44
Message-ID: 27473.1290038204@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Josh Berkus <josh(at)agliodbs(dot)com> writes:
> Ok, I've collected more data.   Looks like the case I was examining was
> idiosyncratic; most of these lock pile-ups involve 400 or more locks
> waiting held by around 20 different backends.  Given this, taking 3
> seconds to sort that all out doesn't seem that unreasonable.
> Presumably there's a poll cycle of some sort for waiting statements?

No ... but if the lock requests were mutually exclusive, I could believe
it taking 3 seconds for all of the waiting backends to get their turn
with the lock, do whatever they were gonna do, commit, and release the
lock to the next guy.

> Anyway, the obvious answer is for the user to fix their application.

Probably.

			regards, tom lane

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