I am currently evaluating the process of upgrading from Firebird 1.54
to 2.03 and have hit a problem. Having saved a 1.54 database and
restored it to 2.03 everything so far seems to work well except the
following query:

select J.JOB_ID,
J.JOB_NUMBER,
C.SHORT_NAME as CUSTOMER_NAME,
B.BRANCH_NAME,
S.DESCRIPTION as JOB_STATUS,
J.CUST_REF_NO
from JOB J,
CUSTOMER C,
BRANCH B,
JOBSTATUS S
where J.JOB_ID LIKE '544%'
and C.CUSTOMER_ID = J.CUSTOMER_ID
and B.BRANCH_ID = J.BRANCH_ID
and S.JOB_STATUS_CODE = J.JOB_STATUS_CODE
order by J.JOB_ID DESCENDING

JOB table has the following index:
CREATE DESCENDING INDEX IX_JOB_ID_DESC ON JOB(JOB_ID);

When executing this query, Firebird 1.54 uses the following plan:
PLAN JOIN (J ORDER IX_JOB_ID_DESC,C INDEX (RDB$PRIMARY66),B INDEX
(RDB$PRIMARY73),S INDEX (RDB$PRIMARY62))
while Firebird 2.03 uses a different plan, as follows:
PLAN SORT (JOIN (C NATURAL, J INDEX (RDB$FOREIGN106), S INDEX
(RDB$PRIMARY62), B INDEX (RDB$PRIMARY73)))
The result is that this query runs very slow on the Firebird 2.03
database because the IX_JOB_ID_DESC index was not utilised in the
plan.

Can anyone shed any light on why this might be happening?

Thanks
Neal Criscuolo