Added to TODO:
* Consider using a hash for joining to a large IN (VALUES ...) list
http://archives.postgresql.org/pgsql-hackers/2007-05/msg00450.php
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Atul Deopujari wrote:
Hi,
Tom Lane wrote:
Neil Conway
Hi,
Tom Lane wrote:
Neil Conway [EMAIL PROTECTED] writes:
When planning queries with a large IN expression in the WHERE clause,
the planner transforms the IN list into a scalar array expression. In
clause_selectivity(), we estimate the selectivity of the ScalarArrayExpr
by calling
Hi,
Tom Lane wrote:
Neil Conway [EMAIL PROTECTED] writes:
When planning queries with a large IN expression in the WHERE clause,
the planner transforms the IN list into a scalar array expression. In
clause_selectivity(), we estimate the selectivity of the ScalarArrayExpr
by calling
Atul Deopujari [EMAIL PROTECTED] writes:
Hi,
Tom Lane wrote:
That's the least of the problems. We really ought to convert such cases
into an IN (VALUES(...)) type of query, since often repeated indexscans
aren't the best implementation.
I thought of giving this a shot and while I was
Hi,
Tom Lane wrote:
Atul Deopujari [EMAIL PROTECTED] writes:
Hi,
Tom Lane wrote:
That's the least of the problems. We really ought to convert such cases
into an IN (VALUES(...)) type of query, since often repeated indexscans
aren't the best implementation.
I thought of giving this a shot
Atul Deopujari [EMAIL PROTECTED] writes:
Yes, letting the planner make its own decision would seem best (in
accordance with what we do for different join paths). But for large IN
lists, a substantial part of the planner is spent in estimating the
selectivity of the ScalarArrayExpr by
Tom Lane wrote:
Atul Deopujari [EMAIL PROTECTED] writes:
Yes, letting the planner make its own decision would seem best (in
accordance with what we do for different join paths). But for large IN
lists, a substantial part of the planner is spent in estimating the
selectivity of the
Is this a TODO?
---
Tom Lane wrote:
Neil Conway [EMAIL PROTECTED] writes:
When planning queries with a large IN expression in the WHERE clause,
the planner transforms the IN list into a scalar array expression. In
When planning queries with a large IN expression in the WHERE clause,
the planner transforms the IN list into a scalar array expression. In
clause_selectivity(), we estimate the selectivity of the ScalarArrayExpr
by calling scalararraysel(), which in turn estimates the selectivity of
*each* array
Neil Conway wrote:
Clearly, the current approach is fine when the array is small -- perhaps
for arrays above a certain number of elements, we could switch to
randomly sampling array elements, estimating their selectivities, and
then using that information to infer the estimated selectivity of
Neil Conway [EMAIL PROTECTED] writes:
When planning queries with a large IN expression in the WHERE clause,
the planner transforms the IN list into a scalar array expression. In
clause_selectivity(), we estimate the selectivity of the ScalarArrayExpr
by calling scalararraysel(), which in turn
-Original Message-
From: [EMAIL PROTECTED] [mailto:pgsql-hackers-
[EMAIL PROTECTED] On Behalf Of Tom Lane
Sent: Thursday, May 10, 2007 11:53 AM
To: Neil Conway
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Planning large IN lists
Neil Conway [EMAIL PROTECTED] writes
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