Re: Mini improvement: statement_cost_limit

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Hans-Jürgen Schönig <postgres(at)cybertec(dot)at>
Subject: Re: Mini improvement: statement_cost_limit
Date: 2008-08-15 23:05:54
Message-ID: 200808151605.56557.josh@agliodbs.com
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Bruce,

> How about a simpler approach that throws an error or warning for
> cartesian products? That seems fool-proof.

Well, throwing a warning is pretty useless for an unattended application.

Also, it's perfectly possible to write queries which will never complete
without a cartesian join.

Basically, *unless* someone has a plan to integrate the greenplum resource
management stuff sometime soon, I think we should take Hans' idea (pending
patch quality, of course). There's an argument to be made that even if we
took the greenplum resource controller, statement_cost_limit would be much
simpler and worth having for the small-effort simple-application users.

FYI, the concept behind the Greenplum RM is similar, except that it
maintains a total "pool" of query costs on a per-role basis.

--
--Josh

Josh Berkus
PostgreSQL
San Francisco

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