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Backend touches index not involved in update / NULL indexing

From: pgsql-bugs(at)postgresql(dot)org
To: pgsql-bugs(at)postgresql(dot)org
Subject: Backend touches index not involved in update / NULL indexing
Date: 2000-11-02 01:40:45
Message-ID: 200011020140.eA21ejw32918@hub.org (view raw or flat)
Thread:
Lists: pgsql-bugs
Doug Mitchell (pgsql(at)dougmitchell(dot)com) reports a bug with a severity of 3
The lower the number the more severe it is.

Short Description
Backend touches index not involved in update / NULL indexing

Long Description
I had some updates that were taking a few seconds each on a primary-keyed table with a few million records.  I dropped an index on a field not involved in the query and the updates now run several times faster.

Idea:  The non-involved field which was indexed with a btree has a lot of NULLs in it.  The btree node with the NULLs (several million records) had to be processed thus slowing performance.  Please provide and document a way to turn on/off the indexing of NULL values.

Either way, PG should not have to update the index in the first place,
because it indexes a field which is not part of the SET or WHERE in the UPDATE statement.

Thanks,
Doug

Sample Code


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