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Re: problem with pg_statistics

From: Manfred Koizar <mkoi-pg(at)aon(dot)at>
To: Andre Schubert <andre(at)km3(dot)de>
Cc: tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-performance(at)postgresql(dot)org
Subject: Re: problem with pg_statistics
Date: 2003-06-27 10:05:14
Message-ID: 555ofvopbsuiog6tti32natah0futga7d4@4ax.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, 27 Jun 2003 11:10:58 +0200, Andre Schubert <andre(at)km3(dot)de>
wrote:
>Once a month we delete the all data of the oldest month.
>And after that a vacuum full verbose analyze is performed.
>Could this cause reordering of the data ?

I may be wrong, but I think VACUUM FULL starts taking tuples from the
end of the relation and puts them into pages at the beginning until
read and write position meet somewhere in the middle.  This explains
the bad correlation.

>And should i do a cluster idx_ts tbl_traffic ?

I think so.

>> >#effective_cache_size = 1000  # default in 8k pages
>> 
>> This is definitely too low.  With 512MB or more I tend to set this to
>> ca. 80% of available RAM.  Use top and free to find hints for good
>> values.
>> 
>
>Ok, i will talk with my coworker ( he is the sysadmin of our machine )
>and look if can use such amount of RAM, because there are several other
>processes that are running on these machines.
>But i will test and report ...

effective_cache_size does not *control* resource consumption,  it just
*reports* it as a hint to the planner.

Servus
 Manfred

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Subject: Large querie with several EXISTS which will be often runned
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