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To: Joe <dev@freedomcircle.net>
cc: Alvaro Herrera <alvherre@commandprompt.com>,
	George Pavlov <gpavlov@mynewplace.com>, pgsql-sql@postgresql.org
Subject: Re: huge disparities in =/IN/BETWEEN performance 
In-reply-to: <1170997319.697.72.camel@pampa> 
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Comments: In-reply-to Joe <dev@freedomcircle.net>
	message dated "Fri, 09 Feb 2007 00:01:59 -0500"
Date: Fri, 09 Feb 2007 09:26:52 -0500
Message-ID: <24132.1171031212@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Joe <dev@freedomcircle.net> writes:
> George didn't provide the inside of his view, but it's
> possible that my earlier example could be rephrased as follows:
> create view v_foo as select * from tab where x < 5;
> select * from v_foo where x = 10;

So try it:

regression=# create table tab (x int);
CREATE TABLE
regression=# create view v_foo as select * from tab where x < 5;
CREATE VIEW
regression=# explain select * from v_foo where x = 10;
                     QUERY PLAN
----------------------------------------------------
 Seq Scan on tab  (cost=0.00..46.00 rows=4 width=4)
   Filter: ((x < 5) AND (x = 10))
(2 rows)

regression=# set constraint_exclusion to 1;
SET
regression=# explain select * from v_foo where x = 10;
                QUERY PLAN
------------------------------------------
 Result  (cost=0.00..0.01 rows=1 width=0)
   One-Time Filter: false
(2 rows)

(This is with HEAD, but I think 8.2 can do it too.)

			regards, tom lane