From: George Essig <george.essig@gmail.com>
To: K C Lau <KCLau@attglobal.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: SELECT DISTINCT Performance Issue
Date: Wed, 8 Jun 2005 08:34:29 -0500
Message-ID: <6744b38505060806342e6a07d@mail.gmail.com> (raw)
In-Reply-To: <6.2.1.2.0.20050602190756.05ab2c70@localhost>
References: <6.2.1.2.0.20050602190756.05ab2c70@localhost>
On 6/2/05, K C Lau <KCLau@attglobal.net> wrote:
...
>
> select DISTINCT ON (PlayerID) PlayerID,AtDate from Player where
> PlayerID='22220' order by PlayerID desc, AtDate desc;
> The Player table has primary key (PlayerID, AtDate) representing data over
> time and the query gets the latest data for a player.
>
>
...
> esdt=> explain analyze select DISTINCT ON (PlayerID) PlayerID,AtDate from
> Player
> where PlayerID='22220' order by PlayerID desc, AtDate desc;
> Unique (cost=0.00..2507.66 rows=1 width=23) (actual time=0.000..187.000
> rows=1 loops=1)
> -> Index Scan Backward using pk_player on player (cost=0.00..2505.55
> rows=8
> 43 width=23) (actual time=0.000..187.000 rows=1227 loops=1)
> Index Cond: ((playerid)::text = '22220'::text)
> Total runtime: 187.000 ms
>
Is PlayerID an integer datatype or a text datatype. It seems like
PlayerID should be an integer data type, but postgres treats PlayerID
as a text data type. This is because the value '22220' is quoted in
your query. Also, the explain analyze output shows "Index Cond:
((playerid)::text = '22220'::text".
George Essig
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To: pgsql-performance@postgresql.org
Cc: george.essig@gmail.com, KCLau@attglobal.net
Subject: Re: SELECT DISTINCT Performance Issue
In-Reply-To: <6744b38505060806342e6a07d@mail.gmail.com>
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