From: | Lukas Smith <smith(at)pooteeweet(dot)org> |
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To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
Subject: | Re: Automatic function replanning |
Date: | 2005-12-22 20:55:14 |
Message-ID: | 43AB12B2.1080803@pooteeweet.org |
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Lists: | pgsql-hackers |
Bruce Momjian wrote:
>> Maybe I am mixing up separate concepts (are bound variables and prepared
>> statements different concepts?) here. I also do not really understand if
>> that means that oracle does not store a query plan for a prepared query
>> or if it just does some special handling in case it knows that a
>> prepared statement column is known to have a highly varying selectivity
>> per value.
>
> What the Oralce manual means I think is that the plan of the query is
> delayed until the _first_ EXECUTE, so it has some values to use in the
> optimizer. The problem is that later queries might use constants of
> greatly different cardinality.
ok .. which just goes to tell to not use prepared statements for a
column with highly varying selectivity ..?
or is there a realistic shot at fixing this use case?
regards,
Lukas
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