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 <
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 Scalar
"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
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:
> 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 wh
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 scalararray
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 scalararray
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. I
> -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
>
> Ne
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
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 th
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 e
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