SV: [firebird-support] general question: calculated fileds vs performance

[Svein Erling Tysvær svein.erling.tysv...@kreftregisteret.no [firebird-support]]

Hello! Generally speaking, regarding performance, is expensive having 
calculated fields?

Not complex ones, I mean this type of thing:



... COMPUTED BY (cast(qty * price * tax / 100 as money 2))

So far I don't notice any difference but I'd like to hear opinions about 
whether is a good

idea using them.



Probably having a real field, maintained with a trigger is better? I don't 
like having redundant

data in my database, but I'm note sure what is the better option: waste a bit 
of space or

(probably) decrease performance??

?
I've heard (don't remember who said it, and since I don't use calculated fields 
much myself, I cannot tell how reliable this information is) that calculated 
fields ought only to refer to the current record, i.e. not a different table or 
different record in the same table. So, as long as qty, price and tax all are 
part of the same record as your COMPUTED BY value, this ought to be fine. If 
they are stored in different lookup tables, then a view or a trigger maintained 
field may be preferrable.

Hopefully, others will verify this or tell that I'm wrong.

Set

[firebird-support] Problem occuers while trying to generate trace file

[babak_...@yahoo.com [firebird-support]]

Hi experts
 

 I would like to trace data base activity in fire bird using Audit/Trace 
Services. I run this command in my command prompt:
 

 C:\Program Files\Firebird\Firebird_2_5\binfbtracemgr -se 
localhost/3050:service_mgr -user SYSDBA -password masterkey -start -name User 
Trace 1 -config fbtrace.conf  C:\Users\Babak\Desktop\trace.out
  
 

 This command generates trace.out file, but I get such an error:
 

 error during fopen operation for file ftrace.conf
 error while trying to open file
 System can not find the file
 

 What should I do to solve these errors?
 

 thank you so much

[firebird-support] Re: general question: calculated fileds vs performance

[brucedickin...@wp.pl [firebird-support]]

If you do not notice any performance then do not worry ahead.
In case of any performance degradation you will easily switch to persistent 
column with trigger on INSERT/UPDATE.