From: Igor Neyman <ineyman@perceptron.com>
To: gmb <gmbouwer@gmail.com>
To: pgsql-sql@postgresql.org <pgsql-sql@postgresql.org>
Subject: Re: View not using index
Date: Tue, 15 Sep 2015 13:29:09 +0000
Message-ID: <A76B25F2823E954C9E45E32FA49D70ECCD515FDC@mail.corp.perceptron.com> (raw)
In-Reply-To: <1442318204445-5865953.post@n5.nabble.com>
References: <1442318204445-5865953.post@n5.nabble.com>
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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?
_______________________
Why are you applying "extra" COALESCE when querying the view?
Why not just:
SELECT * FROM detailview WHERE infor3 = 1;
?
Regards,
Igor Neyman
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To: pgsql-sql@postgresql.org
Cc: ineyman@perceptron.com, gmbouwer@gmail.com
Subject: Re: View not using index
In-Reply-To: <A76B25F2823E954C9E45E32FA49D70ECCD515FDC@mail.corp.perceptron.com>
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