Re: Automatic optimization of IN clauses via INNER JOIN - Mailing list pgsql-performance

From Robert Haas
Subject Re: Automatic optimization of IN clauses via INNER JOIN
Date
Msg-id 603c8f070912171005u557eeedcgaa08f74ffed68b0@mail.gmail.com
Whole thread Raw
In response to Automatic optimization of IN clauses via INNER JOIN  (Thomas Hamilton <thomashamilton76@yahoo.com>)
Responses Re: Automatic optimization of IN clauses via INNER JOIN  (Grzegorz Jaśkiewicz <gryzman@gmail.com>)
List pgsql-performance
On Thu, Dec 17, 2009 at 10:23 AM, Thomas Hamilton
<thomashamilton76@yahoo.com> wrote:
> Apparently the latest version of MySQL has solved this problem:
http://www.xaprb.com/blog/2006/06/28/why-large-in-clauses-are-problematic/
>
> But I am running PostgreSQL v8.3 and am observing generally that SELECT ... WHERE ... IN (a, b, c, ...) is much
slowerthan SELECT ... INNER JOIN (SELECT a UNION ALL SELECT b UNION ALL SELECT c ...) 

That's certainly not MY observation.  It would be interesting to see
what's going on in your case but you'll need to provide more details.

http://wiki.postgresql.org/wiki/Guide_to_reporting_problems

...Robert

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