Re: sunquery and estimated rows

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Markus Bertheau <twanger@bluetwanger.de>
Cc: Litao Wu <litaowu@yahoo.com>, pgsql-performance@postgresql.org
Date: 2004-04-18T23:09:26Z
Lists: pgsql-performance
Markus Bertheau <twanger@bluetwanger.de> writes:
>  , 17.04.2004,  01:45, Tom Lane :
>> The planner sees that as "where scope = <some complicated expression>"
>> and falls back to a default estimate.  It won't simplify a sub-select
>> to a constant.  (Some people consider that a feature ;-).)

> Why?

It's the only way to prevent it from simplifying when you don't want it
to.

			regards, tom lane