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From: Andres Freund <andres@2ndquadrant.com>
To: Дмитрий Дегтярёв <degtyaryov@gmail.com>
Cc: Merlin Moncure <mmoncure@gmail.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Cpu usage 100% on slave. s_lock problem.
Date: Tue, 17 Sep 2013 13:59:26 +0200
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Hi,

On 2013-09-17 17:55:01 +0600, Дмитрий Дегтярёв wrote:
> We have not been able to reproduce this problem on a test servers. Use this
> patch to production servers do not dare.
> 
> In the course of studying the problems we have identified that many queries
> are executed on the slave several times slower. On master function
> heap_hot_search_buffer execute 100 cycles, on the slave the same query with
> the same plan function heap_hot_search_buffer execute 2000 cycles.
> Also, we were able to reproduce the problem on the master and detect that
> there s_lock of slow queries.

What you describe is normally an indication that you have too many
longrunning transactions around preventing hot pruning from working.

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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