From: Richard Huxton <dev@archonet.com>
To: Keith Gray <keith@heart.com.au>
Cc: PostgreSQL Mailing List <pgsql-sql@postgresql.org>
Subject: Re: Slow performance on MAX(primary_key)
Date: Tue, 15 Oct 2002 09:23:15 +0100
Message-ID: <200210150923.15822.dev@archonet.com> (raw)
In-Reply-To: <3DABC801.8060902@heart.com.au>
References: <20021015071628.57518.qmail@web80304.mail.yahoo.com>
<3DABC801.8060902@heart.com.au>
On Tuesday 15 Oct 2002 8:47 am, Keith Gray wrote:
> Ludwig Lim wrote:
> > As of now, Max() doesn't utilizes the indices hence
> > it always do a sequential scan.
>
> Thanks Ludwig,
>
> That does help performance, but I was using a "standard"
> SQL command wrapped in a VB6 ADO ODBC program.
>
> Is this likely to be sorted in 7.2 ?
> Is anyone looking at this?
As I understand, the problem is that the optimisation only applies for simple
cases, and for certain aggregate functions (e.g. not sum()). This means that
the parser would need special-case code to spot these cases, along with tags
for those functions that can be optimised. Thinking further, it might also
vary from type to type. Given that there is a simple workaround and the need
for the optimisation to be added cleanly to the code I believe this has a
fairly low priority.
There is a todo list on the developers' side of the website which has a list
of changes in upcoming releases, you could check there for details.
--
Richard Huxton
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To: pgsql-sql@postgresql.org
Cc: dev@archonet.com, keith@heart.com.au
Subject: Re: Slow performance on MAX(primary_key)
In-Reply-To: <200210150923.15822.dev@archonet.com>
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