Date: Thu, 1 Jun 2006 10:53:28 -0400
From: Alvaro Herrera <alvherre@commandprompt.com>
To: Miroslav ?ulc <miroslav.sulc@startnet.cz>
Cc: pgsql-sql@postgresql.org
Subject: Re: SELECT DISTINCT too slow
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Miroslav ?ulc wrote:
> Well, "key" is not primary key from another table. It is just a column
> in pair "key" => "value".
> The structure of the table is this:
> 
> Id (primary key)
> MRTPContactId (id of contact from table MRTPContact)
> Key (key from pair key => value)
> Value (value from pair key => value)
> 
> So I want the get the list of keys used in the table.

The plan you get is the most efficient possible for that query.  If you
had a table of possible keys (which should of course be FK of "Key"),
you could get a much faster version :-)

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.