> I have a table with 5.900.000 records and a unique index on one
> column. Firebird 1.53.
> I execute the following statement 'select count (*) from table'.
>
> The execution plan informs that the index is not used (Ok, not really
> an issue in this case). But the response time is always different and
> deos not seem to follow any rule (I expected it will decrease and
> take advantage of cached data).
>
> Some example:
> 1st execution takes 2.01 sec.
> 2nd : 7.43 sec
> 3rd : 8.54 sec
> 4th : 3.04 sec
> 5th : 2.03 sec
> 6th : 2.02 sec
>
> Note that no other process was running on the PC.
> How do you explain the response time increases and decreases?

My first guess would be garbage collection - it is asynchronous
in FB1.5, so 1st run initiated it, and it was running during 2nd and 3rd run.
Is that possible ? (You should show us statistics ...)

Ivan