Subject Re: [firebird-support] Plan with udf funtions
Author Svein Erling Tysvaer
Firebird 1.5 cannot index anything but columns (I think). Think about
it, it would be a tremendous amount of waste if it should index every
internal function applied to every field, let alone external functions.
Hence, not even

Select *
from table A

can use an index.

I think Firebird 2.0 can index expressions, but then you have to do
something like

CREATE INDEX MyUDFIndex ON substr(,1,4)

and I doubt (I haven't tried, and would be happy if I'm wrong) that
index could be used with substr(,1,3).


yartax1 wrote:
> Hi,
> One question, did fb 1.5 benefits of indexes with udf functions?
> Example:
> I have next query:
> Select *
> from table A
> where substr(,1,4) = 'EUR_'
> with a index on
> If I run the query, the plan was PLAN(A NATURAL)!!!
> Is that correct?
> Must to create two columns; one with zone and another with zone_prefix
> to benefit of index?
> Thanks.
> Yartax.