Re: SQL statement logging: picking up strange queries from "pg_catalog"

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Graham Leggett <minfrin(at)sharp(dot)fm>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: SQL statement logging: picking up strange queries from "pg_catalog"
Date: 2010-07-03 22:49:31
Message-ID: 18060.1278197371@sss.pgh.pa.us
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Graham Leggett <minfrin(at)sharp(dot)fm> writes:
> I am currently trying to analyse some performance problems within my
> postgresql v8.4.4 database, and after successfully turning sql
> statement logging on, I discover thousands and thousands of queries
> being made what looks like an internal postgresql set of tables in a
> database called "pg_catalog".

> These queries vastly outnumber the queries to the real database, which
> are lost in the noise.

> Does anyone recognise what these statements are for, whether they are
> necessary, and if they aren't necessary, how to switch them off?

I'd bet that you are using a client-side driver that feels a need to
fetch metadata about the tables it's working with. JDBC or ODBC maybe?

A reasonable driver would cache such information, so if there are enough
of these to present a performance issue, maybe the problem is you're
using too short-lived database connections.

regards, tom lane

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