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From: Tom Lane <tgl@sss.pgh.pa.us>
To: adam <adhamm31@hotmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: posgres optimizer not using the index on hstore HELP
Date: Tue, 19 Jul 2016 18:06:50 -0400
Message-ID: <16532.1468966010@sss.pgh.pa.us> (raw)
In-Reply-To: <1468855122279-5912464.post@n5.nabble.com>
References: <1468855122279-5912464.post@n5.nabble.com>
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adam <adhamm31@hotmail.com> writes:
> I have a simple query select on the hstore attribute "EMAIL_ADDRESS". but the
> thing is i'm using a parameter in the query to specify which hstore
> attribute I want to access, and when using a parameter the index which I
> created is suppressed; whereas when I hard code the attribute
> "EMAIL_ADDRESS" then the index is used.

WFM:

regression=# create extension hstore;
CREATE EXTENSION
regression=# create table foo(f1 hstore);
CREATE TABLE
regression=# create index on foo ((f1->'bar'));
CREATE INDEX
regression=# explain select * from foo where f1->'bar' = 'baz';
                                QUERY PLAN                                 
---------------------------------------------------------------------------
 Bitmap Heap Scan on foo  (cost=4.21..14.37 rows=7 width=32)
   Recheck Cond: ((f1 -> 'bar'::text) = 'baz'::text)
   ->  Bitmap Index Scan on foo_expr_idx  (cost=0.00..4.21 rows=7 width=0)
         Index Cond: ((f1 -> 'bar'::text) = 'baz'::text)
(4 rows)

regression=# prepare p as select * from foo where f1->$1 = $2;         
PREPARE
regression=# explain execute p('bar', 'baz');
                                QUERY PLAN                                 
---------------------------------------------------------------------------
 Bitmap Heap Scan on foo  (cost=4.21..14.37 rows=7 width=32)
   Recheck Cond: ((f1 -> 'bar'::text) = 'baz'::text)
   ->  Bitmap Index Scan on foo_expr_idx  (cost=0.00..4.21 rows=7 width=0)
         Index Cond: ((f1 -> 'bar'::text) = 'baz'::text)
(4 rows)

As a general rule, when you haven't mentioned the PG version you're using
nor provided an *exact* example of what you're doing, it's difficult to
offer useful help.

			regards, tom lane


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