Jim C. Nasby írta:

>Those queries aren't the same though. The view is equivalent to
>
>SELECT *
>FROM
> (select 'AAA' AS prefix,id from table 1
> union select 'AAA',id from table 2
> ) view
>WHERE prefix||id = '...'
>
>In this case the prefixes have already been unioned together, so there's
>no chance for the planner to use the function index.
>
>If break the WHERE clause into seperate clauses, such as
>
>WHERE prefix='AAA' AND id = '2005000001'
>
>then I think the planner will know what selects it can simply ignore. If
>that doesn't work, then add 'AAA'||id AS fullid to each of the selects
>in the view and that should allow the function indexes to be used.
>
>

Thanks, both method sworks very fast now and use the expression indexes.
Thanks for the patience and the explanations.

Best regards,
Zoltán Böszörményi


---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to majordomo@postgresql.org so that your
message can get through to the mailing list cleanly