Re: Bug in optimizer

От:

Bruno Wolff III <bruno@wolff.to>

Дата:

4 мая 2004 г. в 13:32:13

On Mon, May 03, 2004 at 18:08:23 +0200,
  Timo Nentwig  wrote:
> 
> This is very slow:

This kind of question should be asked on the performance list.

> 
> SELECT urls.id FROM urls WHERE
> (
> 	urls.id <> ALL (SELECT html.urlid FROM html)
> );
> 
> ...while this is quite fast:

You didn't provide your postgres version or an explain analyze so it is hard
to answer your question definitivly. Most likely you are using a pre 7.4
version which is know to be slow for IN (which is what the above probably
gets translated to).

> 
> SELECT urls.id FROM urls WHERE
> (
> 	NOT (EXISTS (SELECT html.urlid FROM tml WHERE
> 	(
> 		html.urlid = urls.id
> 	)))
> );