Re: Very bad plan when using VIEW and IN (SELECT...*)

Unfortunately I had double-posted this - originally in General.

Tom Lane pointed out (in PG-GENERAL) that the planner will take any IN
(SELECT...) statement and do a JOIN, which is what is causing the planner
problem - even though the SELECT was just returning a constant. Obviously,
the real query this was testing was something more real-world.

SO, I took my original query and turned it to this:

SELECT *
FROM mdx_core.vw_provider AS p
WHERE provider_id = ANY array(
SELECT provider_id
FROM mdx_core.provider_alias
)

BLISTERINGLY fast!

PG version is 8.3 - as for configuration, I didn't want to throw too much
info as my concern was actually whether views were as klunky as other DB
platforms.

Carlo

-----Original Message-----
From: Kevin Grittner [mailto:Kevin(dot)Grittner(at)wicourts(dot)gov]
Sent: August 13, 2010 9:29 AM
To: pgsql-performance(at)postgresql(dot)org; Carlo Stonebanks
Subject: Re: [PERFORM] Very bad plan when using VIEW and IN (SELECT...*)

"Carlo Stonebanks" <stonec(dot)register(at)sympatico(dot)ca> wrote:

> SELECT *
> FROM mdx_core.vw_provider AS p
> WHERE provider_id IN (SELECT 13083101)
>
> I am using the simple IN (SELECT n) in QUERY 2 to simplify the
> problem. I noticed the oddity of the behaviour when I used a
> proper "IN (SELECT myId FROM myTable)"

Did you try?:

SELECT *
FROM mdx_core.vw_provider AS p
WHERE EXISTS (SELECT * FROM myTable WHERE myId = provider_id)

For any follow-up you should probably mention what version of
PostgreSQL this is and how it's configured.

http://wiki.postgresql.org/wiki/SlowQueryQuestions

-Kevin