--- In firebird-support@yahoogroups.com, "Aaron Abend" wrote:

> Set,
>
> Regarding your comment
>
> "If ID is a primary key (PK), then this index is at best useless."
>
> I assume that if you create a primary key on a table that Firebird
> creates a unique index to support that primary key. This is how the
> other databases I use work. Is that why you say the index on ID is
> useless (because it would be a duplicate index)?

Yes, that and knowing that having duplicate indexes in Firebird used
to confuse the optimizer so much that it came up with a hopeless plan
(almost like "Hm, two identical unique indexes - let's go natural").

> All of our indexes are on values with relatively high cardinality,
> so we do not have a lot of duplicates in the value column (this is
> just a simplified example anyway).

Great, that makes things simpler.

Set