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help with correlated delete and outer join

From: "Mike Wertheim" <mike(dot)wertheim(at)linkify(dot)com>
To: <pgsql-general(at)postgresql(dot)org>
Subject: help with correlated delete and outer join
Date: 2004-02-27 01:57:40
Message-ID: KJEEKOANMDIGIAEKHBCDCEMKCCAA.mike.wertheim@linkify.com (view raw or flat)
Thread:
Lists: pgsql-general
I'm using postgresl 7.3.2 and have a query that executes very slowly.

There are 2 tables: Item and LogEvent.  ItemID (an int4) is the primary key
of Item, and is also a field in LogEvent.  Some ItemIDs in LogEvent do not
correspond to ItemIDs in Item, and periodically we need to purge the
non-matching ItemIDs from LogEvent.

The query is:

delete from LogEvent where EventType != 'i' and ItemID in
(select distinct e.ItemID from LogEvent e left outer join Item i
on e.ItemID = i.ItemID where e.EventType != 'i' and i.ItemID is null);

I understand that using "in" is not very efficient.

Is there some other way to write this query without the "in"?





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