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Re: Degrading PostgreSQL 8.4 write performance

From: "Pierre C" <lists(at)peufeu(dot)com>
To: pgsql-performance(at)postgresql(dot)org, "Kabu Taah" <kabuutah(at)hot(dot)ee>
Subject: Re: Degrading PostgreSQL 8.4 write performance
Date: 2011-06-19 23:05:32
Message-ID: op.vxcifizfeorkce@apollo13 (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
>                 Load testing of postgresql 8.4 for OLTP application
> suitability showed that throughput of the
> database significantly degraded over time from thousands of write
> transactions per second to almost zero.

A typical postgres benchmarking gotcha is :

- you start with empty tables
- the benchmark fills them
- query plans which were prepared based on stats of empty (or very small)  
tables become totally obsolete when the table sizes grow
- therefore everything becomes very slow as the tables grow

So you should disconnect/reconnect or issue a DISCARD ALL periodically on  
each connection, and of course periodically do some VACUUM ANALYZE (or  
have autovacuum do that for you).

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