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Re: Re: Hot Standby query cancellation and Streaming Replication integration

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Re: Hot Standby query cancellation and Streaming Replication integration
Date: 2010-03-01 19:21:48
Message-ID: 4B8C13CC.7030908@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-hackers
> So I think the primary solution currently is to raise max_standby_age.
> 
> However there is a concern with max_standby_age. If you set it to,
> say, 300s. Then run a 300s query on the slave which causes the slave
> to fall 299s behind. Now you start a new query on the slave -- it gets
> a snapshot based on the point in time that the slave is currently at.
> If it hits a conflict it will only have 1s to finish before the
> conflict causes the query to be cancelled.

Completely aside from that, how many users are going to be happy with a
slave server which is constantly 5 minutes behind?

--Josh Berkus

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