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From: gmb <gmbouwer@gmail.com>
To: pgsql-sql@postgresql.org
Subject: View not using index
Date: Tue, 15 Sep 2015 04:56:44 -0700 (MST)
Message-ID: <1442318204445-5865953.post@n5.nabble.com> (raw)
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HI 

I hope somebody can give some guidance.
Since our application make extensive use of views, this is becoming a
concern for me.

Please see below:

CREATE TABLE detail ( invno VARCHAR, accno INTEGER, info INTEGER[] );

CREATE OR REPLACE VIEW detailview AS 
( SELECT invno , accno , COALESCE( info[1],0 ) info1, COALESCE( info[2],0 )
info2, COALESCE( info[3],0 ) info3, COALESCE( info[4],0 ) info4 FROM detail
);

CREATE INDEX detail_ix_info3 ON detail ( ( info[3]  ) ) WHERE  COALESCE(
info[3],0 ) = 1;

EXPLAIN SELECT * FROM detail WHERE COALESCE( info[3],0 ) =1;

                                  QUERY PLAN                                  
------------------------------------------------------------------------------
 Bitmap Heap Scan on detail  (cost=4.13..12.59 rows=4 width=68)
   Recheck Cond: (COALESCE(info[3], 0) = 1)
   ->  Bitmap Index Scan on detail_ix_info3  (cost=0.00..4.13 rows=4
width=0)
(3 rows)

EXPLAIN SELECT * FROM detailview WHERE COALESCE( info3,0 ) =1;

                       QUERY PLAN                       
--------------------------------------------------------
 Seq Scan on detail  (cost=0.00..20.38 rows=4 width=68)
   Filter: (COALESCE(COALESCE(info[3], 0), 0) = 1)
(2 rows)


This is an oversimplified example; the view in our production env provides
for 20 elements in the info array column. My table in productions env
contains ~10mil rows.

Is there any way in which I can force the view to use the index?


Regards




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