From: Vladimir Kamarzin <vvk@vvk.pp.ru>
To: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Performance degradation in 324577f39bc8738ed0ec24c36c5cb2c2f81ec660
Date: Wed, 08 Oct 2014 14:40:23 +0600
Message-ID: <2012271412757623@web3g.yandex.ru> (raw)
In-Reply-To: <22483.1412690194@sss.pgh.pa.us>
References: <29191412676815@web25o.yandex.ru>
<22483.1412690194@sss.pgh.pa.us>
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07.10.2014, 19:59, "Tom Lane" <tgl@sss.pgh.pa.us>:
> Vladimir Kamarzin <vvk@vvk.pp.ru> writes:
>> After upgrade from 9.3.1 to 9.3.5 we expirienced a slight performance degradation of all queries. Query time increased to some amount of ms, mostly in range of 100ms. Some actions in our application results in a lot of small queries and in such cases performance degradation is very significant - total action performs for a 2-3 times longer then before (15s -> 40s, etc).
>> Using git-bisect we've found a bad revision causes performance drop: it is 324577f39bc8738ed0ec24c36c5cb2c2f81ec660
>
> Hm. If you're going to do queries that involve update/delete across large
> inheritance trees, that bug fix is unavoidably going to cost you some
> cycles.
Yeah, we're actually noticed significantly increased CPU load while running on 9.3.5.
> I am wondering if you've
> misidentified the commit that made the difference --- especially since you
> claim there's a penalty for "all" queries, which there manifestly couldn't
> be with this particular patch.
No, problem appears exactly on this commit. Actually I don't really sure about "all": we don't see degradation when performing plain SELECTs manually,
but comparing logged query time of some SELECTs we see the differences.
Here is example 42ms -> 250ms:
http://pastebin.ca/2855292http://pastebin.ca/2855290> If not, there must be something rather
> unusual about your queries or schema. Care to provide a self-contained
> test case?
I'm afraid we cannot do this now. If you wish, we can give you ssh access to the test server to investigate the problem.
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To: pgsql-performance@postgresql.org
Cc: vvk@vvk.pp.ru
Subject: Re: Performance degradation in 324577f39bc8738ed0ec24c36c5cb2c2f81ec660
In-Reply-To: <2012271412757623@web3g.yandex.ru>
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