Subject Join, SP and ORDER BY: strange behaviour
Author Nando Dessena
for some reason I have to code an inner join like this:

select A.*
from ATABLE A join ASTOREDPROC(<parameters>) SP
order by A.AFIELD

Let ASTOREDPROC be a stored procedure that simply performs for select
KEYFIELD from ATABLE into ... do.

The resultset is NOT ordered by A.AFIELD if AFIELD is indexed, unless it
is KEYFIELD (I have 4 indexes on ATABLE: one on KEYFIELD and three on
three other fields, one field each: the order by won't work on those
three only).

The problem goes away if I:
- request a descending sort, or
- use a left join (SP left join table, which in my case is equivalent),
- remove/deactivate the index, or
- remove the join with the SP

As a side note, if I use a left join (which is what I am planning to do
if no better solution arises), the plan shown says IB is not using the
existing index for sorting (IB knows better than me anyway, I suppose).
I am using IB5.6.
Sounds like a bug of some kind.
Any thoughs?