>> > in this table around 50 000 000 records (and 20 fields)
>> >
>> > this index are motly here because we need to handle search and order for client in < 100 ms. so we need to index all possible
>> > case
>> > of search
>>
>> But ordering using index is quite slow on the table of that size, your quieries will usually be slower than 100 ms anyway.

> by ordering using index is slow, you mean in the insert (updating the index) or you mean in the select (using the select) ?

Yes, SELECT. Can you try yourself ? Construct SELECT statement with WHERE clause that will return e.g. 150 rows,
and execute it on your 50 000 000 records table, once ORDERed by index, once withou index, and compare the times.
(and use different fields for search condition and for ordering)
(for easy switching between ordering with/without index, use ASC/DESC in your order clause)

Ivan
http://www.volny.cz/iprenosil/interbase/