Horton

Re: Optimizer : query rewrite and execution plan ?

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

View thread
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: theo@flame.co.za, pgsql-performance@postgresql.org
Date: 2008-02-11T16:44:42Z
Lists: pgsql-performance 
Simon Riggs <simon@2ndquadrant.com> writes:
> Say if cost of best plan >= N then recheck query for strangeness. If
> anything found, re-plan query.

Whatever makes you think that would be useful?

The usual result of undetected duplicate WHERE clauses is an
*underestimate* of runtime, not an overestimate (because it thinks
too few tuples will be selected).

			regards, tom lane