| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | Stephen Davies <scldad(at)sdc(dot)com(dot)au> |
| Cc: | Michael Glaesemann <grzm(at)seespotcode(dot)net>, Russell Smith <mr-russ(at)pws(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Optimising "in" queries |
| Date: | 2007-08-23 19:46:42 |
| Message-ID: | 20070823194642.GD31461@alvh.no-ip.org |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
Stephen Davies wrote:
> Interesting semantics. I have never seen the IN syntax referred to as
> "array processing" before.
>
> I have always thought of array processing as the thing that vector
> processors such as Cray and ETA do/did.
>
> While superficially equivalent, I have always believed that IN (a,b,c)
> executed faster than =a or =b or =c. Am I wrong for PostgreSQL?
Older versions of Postgres translated IN (a, b, c) into an OR'ed list of
equalities. Nowadays it is treated as an array; I think it's translated
to = ANY ({a,b,c}), as you can see in the message you posted at the
start of this thread.
I don't think you showed us the EXPLAIN ANALYZE results that Scott
requested.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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