Subject select on deleted data - bad performance
Author Robert Zimmermann
Hello again,

I'm having some trouble here. I've got a few tables being filled up with data periodically. Some procedures then process the data and another application exports it to a disk file - My application then deletes the table (delete from tablename).
Meanwhile some other procedures and frontend applications are checking the table and it's recordcount (select * / count(*) from tablename) and, to my surprise, this is incredible slow.
Recordcount of the table is ~60.000 records, each containing 10 numerics. Usually not that much data to cause trouble. I played a bit around and tested some statements:

deletion of all ~60.000 records - ~500 msec
select count(*) / * from table (table is completely empty after deletion) ~ 5 minutes !!

After select * or count(*) once is finished (after 5 minutes ^^), every following statement will execute normally ( few msecs ). Table is indexed (primary key on integer column).

Whats happening here? Looking at the task manager theres no significant CPU load. The fb client seems to do nothing during execution (load of client process ~ 5% / ~20% other / ~75% idle)
Any suggestions?

Sys specs:
Athlon64 3400+, 1g RAM, 2x7200rpm SATA Disks @Raid0, Win2000
Running Firebird 2.1 classic server

Greetingz,

Robert
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