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Re: Massive update, memory usage

From: Andreas Kretschmer <akretschmer(at)spamfence(dot)net>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Massive update, memory usage
Date: 2010-10-27 18:58:04
Message-ID: 20101027185804.GA15814@tux (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Trenta sis <trenta(dot)sis(at)gmail(dot)com> wrote:

> Hi,
> I have a Linux Server (Debian) with Postgres 8.3 and I have problems with a
> massive update, about 400000 updates/inserts.

Updates or Inserts?

> If I execute about 100000 it seems all ok, but when I execute 400000, I have
> the same problem with or without a transaction (I need to do with a
> transaction) increase memory usage and disk usage.
> With a execution of 400.000 inserts/update server begin woring well, but after
> 100 seconds of executions increase usage of RAM, and then Swap and finally all
> RAM and swap are used and execution can't finish.
> I have made some tuning in server, I have modified:
> -shared_buffers 1024 Mb
> -work_mem 512 Mb

Way too high, but that's not the problem here... (i guess, depends on
the real query, see below about explain analyse)

> -effective_cache_size 2048Mb

You have 4GB, but you are defined only 1 GByte for shared_mem and you
have defined only 2GB for shared_mem and os-cache together. What about
the other 2 GByte?

> -random_page_cost 2.0

you have changed the default, why?

> -checkpoint_segments 64
> -wal_buffers 8Mb
> -max_prepared_transaction 100
> -synchronous_commit off
> what is wrong in this configuration to executes this inserts/update?

Hard to guess, can you provide the output generated from 
EXPLAIN ANALYSE <your query>?

> Server has: 4Gb RAM, 3GB Swap and SATA Disk with RAID5

RAID5 isn't a good choise for a database server...

Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

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