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Message-ID: <dcc563d10708220743h37f85ae5scb183bb9e6e85073@mail.gmail.com>
Date: Wed, 22 Aug 2007 09:43:00 -0500
From: "Scott Marlowe" <scott.marlowe@gmail.com>
To: "Aleksandr Vinokurov" <aleksandr.vin@gmail.com>
Subject: Re: Partial index and query plan
Cc: pgsql-sql@postgresql.org
In-Reply-To: <b048c51b0708220557g18cc9a6p7bf2ab195539c3bd@mail.gmail.com>
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References: <b048c51b0708220557g18cc9a6p7bf2ab195539c3bd@mail.gmail.com>

On 8/22/07, Aleksandr Vinokurov <aleksandr.vin@gmail.com> wrote:
>
> create table user_history (
>    rec_id               SERIAL not null,
>    date                 TIMESTAMP            not null,
>    action               INT2                 not null,
>    uid                  INT4                 not null,
>    name                 CHAR(10)             null default NULL,
>    constraint PK_USER_HISTORY primary key (rec_id),
>    constraint AK_DATE_USER_HIS unique (date)
> );
>
> create unique index indx_date_action12_uid_user_his
> on user_history (date, uid)
> where action <> 0;
>
> and this query:
>
> select date
> from "user_history"
> where date > '2007-08-18 14:33'
> and date <= '2007-08-18 16:30'
> and uid = 1388
> and action <> 0
> limit 1;
>
>
> The question is why "explain analyze" shows a 'Filter: ("action" <> 0)' in plan:
>
> Limit  (cost=0.00..3.05 rows=1 width=8) (actual time=4.798..4.798
> rows=0 loops=1)
>    ->  Index Scan using indx_date_action12_uid_user_his on
> user_history  (cost=0.00..6.10 rows=2 width=8) (actual
> time=4.791..4.791 rows=0 loops=1)
>          Index Cond: ((date > '2007-08-18 14:33:40.60664'::timestamp
> without time zone) AND (date <= '2007-08-18 16:30:00'::timestamp
> without time zone) AND (uid = 138658))
>          Filter: ("action" <> 0)

I don't see the issue here.  The index being used is the same partial
index you created.  Maybe it's just a question of semantics?