Question to improve the performances of applications, i use 'repeated select' in my programs.
when the application runs, the define query is done more than one time for the same query. it should be done one time only.
do you know why ?
Answer Hello,
First, sorry to answer a little in late ...
"repeated select" only tell to the dbms to store the QEP in it's memory. So when the query is defined the second time, DBMS do not have to recalculate it. It was true only and only if the same query is running (do not hope the "repeated" run along the same table thru differents query's (ie differents where clause).
In the past with an other DBA whe made a loop program (Embeded/C) to "mesure" performance of our information system. The loop consist to a "repeated select" on the main and bigget table with a blank key (to ensure each time the DBMS scan all the table) and then output the elaps time of the query. The first run take seconds (2 ou 3), and the others less than one.
Hope this is clear (i'am french so my english could be sometimes a little poor :-) and help you,
Jean-Pierre ZUATE
