Re: slow query execution

[Trigve Siver <trigves(at)yahoo(dot)com>]

Hi, 
Thanks for reply, As you have mentioned I need to get row numbers for my query, so when I make some other query with same data I will know which row number has a particular ID. As you mentioned "You can
do this with a temporary sequence, among other approaches...". Can you point me to some sources or give me some examples, please?

Thanks 

Trigve

----- Original Message ----
From: Andrew Sullivan <ajs(at)crankycanuck(dot)ca>
To: pgsql-sql(at)postgresql(dot)org
Sent: Wednesday, May 30, 2007 6:45:53 PM
Subject: Re: [SQL] slow query execution

On Wed, May 30, 2007 at 08:56:45AM -0700, Trigve Siver wrote:
> Hi all,
> 
> This query executes very slow:
> 
> select (select count(*) from customer where id <= a.id) as row, id,
> from customer as a order by id;

So you are trying to get the ordinal position of every ID in the
table?  I'm not surprised it takes a long time -- you have to join
the whole table to itself and then do a lot of counting.  Are you
just trying to get the "row number" for your query answer?  You can
do this with a temporary sequence, among other approaches, more
cheaply.

A


-- 
Andrew Sullivan  | ajs(at)crankycanuck(dot)ca
Users never remark, "Wow, this software may be buggy and hard 
to use, but at least there is a lot of code underneath."
        --Damien Katz

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