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	Tue, 15 Oct 2002 00:16:28 PDT
Date: Tue, 15 Oct 2002 00:16:28 -0700 (PDT)
From: Ludwig Lim <lud_nowhere_man@yahoo.com>
Subject: Re: Slow performance on MAX(primary_key)
To: Keith Gray <keith@heart.com.au>
Cc: PostgreSQL Mailing List <pgsql-sql@postgresql.org>
In-Reply-To: <3DABA146.7010902@heart.com.au>
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Hi Keith:

--- Keith Gray <keith@heart.com.au> wrote:
> Help,
> 
> I have just been comparing some large table
> performance
> under 7.1 using the
> 
> 	select max(primary key)from table;
> 
> We are using this for various functions including
> sequence.
> 

  Try using the following as alternative :
  
  SELECT primary_key
  FROM table
  ORDER BY primary_key desc
  LIMIT 1;

  This should work if primary_key is indexes.

  As of now, Max() doesn't utilizes the indices hence
it always do a sequential scan.

  Hope that helps,

regards,
ludwig.







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