From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andreas Kretschmer <akretschmer@spamfence.net>
cc: "Huang, Suya" <Suya.Huang@au.experian.com>,
 pgsql-performance@postgresql.org
Subject: Re: GIN index not used
In-reply-to: <20140711044452.GA7390@tux>
References: 
 <D83E55F5F4D99B4A9B4C4E259E6227CD014C3263@AUX1EXC01.apac.experian.local>
 <20140711044452.GA7390@tux>
Comments: In-reply-to Andreas Kretschmer <akretschmer@spamfence.net>
 message dated "Fri, 11 Jul 2014 06:44:52 +0200"
Date: Fri, 11 Jul 2014 00:56:14 -0400
Message-ID: <20680.1405054574@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

Andreas Kretschmer <akretschmer@spamfence.net> writes:
> Huang, Suya <Suya.Huang@au.experian.com> wrote:
>> I’ve got a table with GIN index on integer[] type. While doing a query with
>> filter criteria on that column has GIN index created, it’s not using index at
>> all, still do the full table scan. Wondering why?

> Btw.: works for me:

Yeah, me too:

regression=# create table booking_weekly(booking_ts int[]);
CREATE TABLE
regression=# create index on booking_weekly using gin (booking_ts);
CREATE INDEX
regression=# explain select * from booking_weekly where booking_ts@>array[2446685];
                                         QUERY PLAN                                         
--------------------------------------------------------------------------------------------
 Bitmap Heap Scan on booking_weekly  (cost=8.05..18.20 rows=7 width=32)
   Recheck Cond: (booking_ts @> '{2446685}'::integer[])
   ->  Bitmap Index Scan on booking_weekly_booking_ts_idx  (cost=0.00..8.05 rows=7 width=0)
         Index Cond: (booking_ts @> '{2446685}'::integer[])
 Planning time: 0.862 ms
(5 rows)

What PG version is this?  What non-default planner parameter settings are
you using?  (Don't say "none", because I can see you've got enable_seqscan
turned off.)

			regards, tom lane


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