From: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
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To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [GENERAL] Performance issue with libpq prepared queries on 9.3 and 9.4 |
Date: | 2014-11-14 00:43:45 |
Message-ID: | 1415925825145-5826921.post@n5.nabble.com |
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Lists: | pgsql-general pgsql-hackers |
Tom Lane-2 wrote
> In the meantime, I assume that your real data contains a small percentage
> of values other than these two? If so, maybe cranking up the statistics
> target would help. If the planner knows that there are more than two
> values in the column, I think it would be less optimistic about assuming
> that the comparison value is one of the big two.
Is there any value (or can value be added) in creating a partial index of
the form:
archetype IN ('banner','some other rare value')
such that the planner will see that such a value is possible but infrequent
and will, in the presence of a plan using a value contained in the partial
index, refuse to use a generic plan knowing that it will be unable to use
the very specific index that the user created?
David J.
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