DENNIS WILLIAMS wrote: > > Stephane > You mentioned "each additional index costs about 2.5 times the cost of > inserting into a non-indexed table". I just wanted to point out that Kevin > Loney has done some performance tests involving the number of indexes. I > don't know if he has published these anywhere. In a nutshell, the results > were that a single index really hurts insert performance, and each > additional index increases the hurt, but by a decreasing amount. The > conclusions were: > - If you can drop all indexes, that will really help inserts. > - If you have one index, adding a second index will really hurt, but not > as bad. > - If the table already has 15 indexes, adding one more index probably > won't be noticed. > > Dennis Williams > DBA, 40%OCP > Lifetouch, Inc. > [EMAIL PROTECTED] >
Dennis, I have also benched it, and what I gave are my results. Note that we totally agree in _relative_ terms. If you have 15 indexes, I estimate the cost to be about 100 + 15 * 250, so in truth at this stage the cost of an index is about 7% ... Note also that the costs I gave are relative to the number of logical reads. I have met a number of cases when a significant increase in logical reads was hardly noticeable in terms of elapsed time. -- Regards, Stephane Faroult Oriole Software -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Stephane Faroult INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
