From: Stephan Szabo <sszabo@megazone.bigpanda.com>
To: Tomas Skäre <tomas@nocrew.org>
Cc: pgsql-general@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: Query is not using index when it should
Date: Fri, 10 Dec 2004 18:28:38 -0800 (PST)
Message-ID: <20041210182453.G92467@megazone.bigpanda.com> (raw)
In-Reply-To: <80oeh2tm7x.fsf@junk.nocrew.org>
References: <80oeh2tm7x.fsf@junk.nocrew.org>
On Fri, 10 Dec 2004, Tomas [iso-8859-1] Skäre wrote:
> I have a table that looks like this:
>
> Table "public.cjm_object"
> Column | Type | Modifiers
> -----------+-------------------+-----------
> timestamp | bigint | not null
> jobid | bigint | not null
> objectid | bigint | not null
> class | integer | not null
> field | character varying | not null
In 7.4.x and earlier, you need to cast the value you're comparing to into
a bigint in order to make sure the indexes are used (in your timestamp
case it appears to work because the value doesn't fit in a plain integer).
8.0 should handle this better.
> But when doing a search with objectid, class and field, it doesn't use
> the idx_cjm_object1 index.
> db=# explain analyze select * from cjm_object where objectid=4534 and class=12 and field='paroid';
Using one of
objectid=4534::bigint
objectid='4534'
objectid=CAST(4534 as bigint)
rather than objectid=4534 should make this indexable in 7.4.x.
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To: pgsql-sql@postgresql.org
Cc: sszabo@megazone.bigpanda.com, tomas@nocrew.org, pgsql-general@postgresql.org, pgsql-performance@postgresql.org
Subject: Re: Query is not using index when it should
In-Reply-To: <20041210182453.G92467@megazone.bigpanda.com>
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