> This is caused by a semi-well known weakness in the optimizer.
> The optimizer
> rewrites the WHERE clause in conjunctive normal form (CNF):
>
> (A and B) or (C and D) ==> (A or C) and (A or D) and (B or C)
> and (B or D)
>
Wouldn't disjunctive normal form be better, since it can be implemented as
the simple union of a set of small queries?
Taral