Subject: Re: Does Postgresql have a similar pseudo-column "ROWNUM" as
From: Ragnar =?ISO-8859-1?Q?Hafsta=F0?= <gnari@simnet.is>
To: Alain <alainm@pobox.com>
Cc: Sql-Postgre <pgsql-sql@postgresql.org>
In-Reply-To: <428AA569.3010708@pobox.com>
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Date: Wed, 18 May 2005 08:28:25 +0000
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On Tue, 2005-05-17 at 23:16 -0300, Alain wrote:
> 
> Ragnar Hafstað escreveu:
> >>[how to solve the get next 100 records problem]

> BUT, I think that this is close to a final solution, I made some 
> preliminary test ok. Please tell me what you think about this.
> 
> Fisrt let's state that I am reading records to put on a screen (in a 
> Table/Grid). I separated the problem is *3* parts
> 
> -first select is as above:
> select ... from tab ORDER by skey,pkey LIMIT 100;
> 
> -second method for next 100:
> select ... from tab WHERE skey>=skey_last
>                      ORDER BY skey,pkey
>                      LIMIT 100;
> but here I test for repetitions using pkey and discard them
> 
> -now if I get all repetitions or the last 100 have the same skey with 
> the second method, I use
> select ... from tab WHERE skey=skey_last AND pkey>pkey_last
>                      ORDER BY skey,pkey
>                      LIMIT 100;
> until I get an empty response, then I go back to the second method.

if your distribution is such that those skeys that have > 100 records
tend to have a lot more, you might have a higher limit for this case.


> All queries are extremely fast with 6000000 records and it looks like 
> the few redundant or empty queries (but very fast) will not be a problem.
> 
> What is your opinion about this (apart that it is a bit complex :) ??


looks fine

gnari