Re: Using Bitmap scan instead of Seq scan - Mailing list pgsql-general

From David Johnston
Subject Re: Using Bitmap scan instead of Seq scan
Date
Msg-id 028a01cbcc70$a3d85ba0$eb8912e0$@yahoo.com
Whole thread Raw
In response to Using Bitmap scan instead of Seq scan  (Ahmed Ossama <ahmed@aossama.net>)
Responses Re: Using Bitmap scan instead of Seq scan  (Jon Nelson <jnelson+pgsql@jamponi.net>)
List pgsql-general
You cannot ALWAYS do an indexed scan - sometimes the only option for the
parser is to do a sequential scan (thus you can say "avoid unless you have
to" but you can never truly disable sequential scanning).

Given limited knowledge of full-text searching I cannot explain why this
specific query is unable (or unwilling) to use an index.  Since you have not
provided any index options for the list to consider we may even assume you
have NO indexes and thus none to choose from...

I'd suggest looking at chapters 11 (Indexes) and 12 (Full-Text) of the
documentation while awaiting further responses from the list (after you
describe what indexes you have already defined on relevant tables - and
maybe provide the raw query as well).

David J


-----Original Message-----
From: pgsql-general-owner@postgresql.org
[mailto:pgsql-general-owner@postgresql.org] On Behalf Of Ahmed Ossama
Sent: Monday, February 14, 2011 12:40 PM
To: pgsql-general@postgresql.org
Subject: [GENERAL] Using Bitmap scan instead of Seq scan

I did a REINDEX and ANALYZE on the table, disabled the seqscan and ran the
query again with the same result.

My question how do I make PostgreSQL always uses bitmap scan instead of seq
scan?

Any advice is very much appreciated.

Best Regards,
Ahmed Ossama

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