From: Craig A. James <cjames@modgraph-usa.com>
To: Spiegelberg, Greg <gspiegelberg@cranel.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: DELETE with filter on ctid
Date: Mon, 09 Apr 2007 14:57:35 -0700
Message-ID: <461AB6CF.3060202@modgraph-usa.com> (raw)
In-Reply-To: <82E74D266CB9B44390D3CCE44A781ED90B6ADC@POSTOFFICE.cranel.local>
References: <82E74D266CB9B44390D3CCE44A781ED90B6ADC@POSTOFFICE.cranel.local>
Spiegelberg, Greg wrote:
> We have a query which generates a small set of rows (~1,000) which are
> to be used in a DELETE on the same table. The problem we have is that
> we need to join on 5 different columns and it takes far too long.
You may have encountered the same problem I did: You *must* run ANALYZE on a temporary table before you use in another query. It's surprising that this is true even for very small tables (a few hundred to a few thousand rows), but it is. I had a case where I created a "scratch" table like yours, and the before/after ANALYZE performance was the difference between 30 seconds and a few milliseconds for the same query.
Craig
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To: pgsql-performance@postgresql.org
Cc: cjames@modgraph-usa.com, gspiegelberg@cranel.com
Subject: Re: DELETE with filter on ctid
In-Reply-To: <461AB6CF.3060202@modgraph-usa.com>
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