[Mondrian] Re: Performance degradation

Peter Tran ptran at prospricing.com
Tue Mar 3 17:45:08 EST 2009


Matt,

Are you doing native evaluation?  We found a case where Mondrian was doing non-native evaluation based on how the MDX was structured which had a huge impact on performance.

Check to see whether the crossjoin is being pushed down natively to the database.

-Peter

________________________________
From: mondrian-bounces at pentaho.org [mailto:mondrian-bounces at pentaho.org] On Behalf Of Matt Campbell
Sent: Tuesday, March 03, 2009 4:25 PM
To: Mondrian developer mailing list
Subject: [Mondrian] Re: Performance degradation

I was able to reproduce this issue with a very simple Foodmart query.  The following runs in under 2 seconds with changelist 10915.  It now takes around 55 seconds with 12403.   From the little investigation I've done it looks like most time is spent in executeStripe().

It's interesting, if I eliminate either part of the set the time drops back down to ~2 seconds--i.e. eliminate either the GENERATE() or the {Product.DEFAULTMEMBER, [Yearly Income].DEFAULTMEMBER}.  If they are both present, though, it takes 55 seconds.

SELECT
            {GENERATE({[Product].[Product Name].MEMBERS},
             CROSSJOIN( {([Product].CURRENTMEMBER)},
           {[Yearly Income].[Yearly Income].MEMBERS}), ALL),
            {([Product].DEFAULTMEMBER,[Yearly Income].DEFAULTMEMBER)}
}
 ON AXIS(0)
FROM
            [Sales] ;


On Tue, Mar 3, 2009 at 11:03 AM, Matt Campbell <mkambol at gmail.com<mailto:mkambol at gmail.com>> wrote:

During a run of a performance test we noticed a fairly significant increase in query time for queries involving very large numbers of cells.  We actually hadn't run this particular test in nearly a year, so the comparison is between changelist 10915 and 12403.

The query is ridiculously large--nearly 200K tuples, intersected with 12 measures.  With 10915 this query ran in a little over an hour.  With 12403 it runs for over 5 hours.

I haven't investigated much yet.  I'm going to create simple Foodmart query to try to reproduce, and then I'll try to narrow down where the bottleneck is.  I wanted to post, though, in case anyone has thoughts about this.



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