| Subject | Re: Optimiser chooses wrong plan? |
|---|---|
| Author | Svein Erling Tysvær |
| Post date | 2004-10-08T11:50:07Z |
Hi Filip!
and do not change. The chances of changing I think are limited to the
system generated index names - e.g. rdb$primary44.
A.LYDGBKJ+0 = B.LYDCBKJ
The +0 prevents the "poor" plan, whereas the "good" plan still can be
used. If LYDGBKJ is a character field, use
A.LYDGBKJ || '' = B.LYDCBKJ
This should help,
Set
> You wrote:In your case yes - they are safe. The names have been chosen by you
>
>
> Hi,
>
> Firebird 1.5 optimiser chooses wrong plan on following query. I
> can't figure out why it does so or how to correct it. The only
> sollution i found was to change the first inner join by a left join
> or to use an explicited plan.
>
> Could someone help me out, i prefer not to use explicited plans. Are
> explicited plans safe to use with regard to backup/restore DBs (Risc
> of changed Index Names)?
and do not change. The chances of changing I think are limited to the
system generated index names - e.g. rdb$primary44.
> SELECT ...change to
> FROM
> LYDGB A
> INNER JOIN
> LYDOC B
> on
> A.LYDGBKJ = B.LYDCBKJ AND
> A.LYDGCODE = B.LYDCDGB
A.LYDGBKJ+0 = B.LYDCBKJ
The +0 prevents the "poor" plan, whereas the "good" plan still can be
used. If LYDGBKJ is a character field, use
A.LYDGBKJ || '' = B.LYDCBKJ
This should help,
Set