Hello,

>> What about the performance in FB with your original SELECT MAX...
>> after adding DESC index? And memory usage with FB?

d> I added both index and desc index to that field, using the command
d> below:

d> CREATE INDEX IX_A ON TABLE_X (field_A);
d> CREATE DESC INDEX IX_A_DE ON TABLE_X (field_A);

d> but seems not worked.
d> The execution will still take as long time as before.
d> and so is memory usage.

Could you please post execution plans for your original query

SELECT MAX(field_A) as max_A, field_B FROM TABLEX GROUP BY field_B

without and with DESC index in the database? You could try DESC
index on (field_B, field_A) also.



--
Best regards,
Pavel Menshchikov
http://www.ls-software.com