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Re: Reducing stats collection overhead

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Arjen van der Meijden <acm(at)tweakers(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Reducing stats collection overhead
Date: 2007-07-31 03:07:07
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Lists: pgsql-hackers
Arjen van der Meijden wrote:
> Afaik Tom hadn't finished his patch when I was testing things, so I don't 
> know. But we're in the process of benchmarking a new system (dual quad-core 
> Xeon) and we'll have a look at how it performs in the postgres 8.2dev we 
> used before, the stable 8.2.4 and a fresh HEAD-checkout (which we'll call 
> 8.3dev). I'll let you guys (or at least Tom) know how they compare in our 
> benchmark.

So, ahem, did it work? :-)

> On 18-5-2007 15:12 Alvaro Herrera wrote:
>> Tom Lane wrote:
>>> Arjen van der Meijden told me that according to the
>>> benchmark, HEAD is noticeably slower than 8.2.4, and I soon confirmed
>>> here that for small SELECT queries issued as separate transactions,
>>> there's a significant difference.  I think much of the difference stems
>>> from the fact that we now have stats_row_level ON by default, and so
>>> every transaction sends a stats message that wasn't there by default
>>> in 8.2.  When you're doing a few thousand transactions per second
>>> (not hard for small read-only queries) that adds up.
>> So, did this patch make the performance problem go away?

Alvaro Herrera                      
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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