Re: sunquery and estimated rows

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

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Rod Taylor <rbt@rbt.ca>
Cc: Markus Bertheau <twanger@bluetwanger.de>, Litao Wu <litaowu@yahoo.com>, Postgresql Performance <pgsql-performance@postgresql.org>
Date: 2004-04-19T02:16:53Z
Lists: pgsql-performance
Rod Taylor <rbt@rbt.ca> writes:
>> It's the only way to prevent it from simplifying when you don't want it
>> to.

> I'm having a difficult time coming up with a circumstance where that is
> beneficial except when stats are out of whack.

Try trawling the archives --- I recall several cases in which people
were using sub-selects for this purpose.

In any case, I don't see the value of having the planner check to see if
a sub-select is just a trivial arithmetic expression.  The cases where
people write that and expect it to be simplified are so few and far
between that I can't believe it'd be a good use of planner cycles.

			regards, tom lane