[Mondrian] Mondrian Performance Issue with Large Dimensions

Joe Barnett thejoe at gmail.com
Tue Oct 18 10:47:24 EDT 2011


Possible that this is http://jira.pentaho.com/browse/MONDRIAN-811 ?
Sounds like it's related to the order of dimension definition, which
would correspond to what we saw there (and work around by putting the
large dimensions toward the end of our schema definition).

-Joe

On Tue, Oct 18, 2011 at 12:47 AM, Tom Barber <tom at analytical-labs.com> wrote:
> Hi Julian,
>
> I got them to check the mondrian property in
> system/mondrian/mondrian.properties, and I'm told its already set to true. I
> should also point out this when using Analyzer.
>
> Cheers
>
> Tom
>
> On 18 October 2011 08:19, Julian Hyde <jhyde at pentaho.com> wrote:
>>
>> Pedro asked me a similar question. See my reply to him (below).
>>
>> It turns out that option #1 is already implemented. Try setting
>> mondrian.olap.elements.NeedDimensionPrefix=true and see whether mondrian
>> generates fewer SQL queries. (You'll have to write more explicit MDX of
>> course.)
>>
>> Julian
>>
>> -------
>>
>> On Saturday, September 24, 2011, Julian Hyde wrote:
>>
>> > Ideas to improve "large dimension" performance:
>> >
>> > 1. Add option that forces strict name resolution. You would not be able
>> > to write [M], you would have to write [Gender].[M]. Therefore if you wrote
>> > [Customers] mondrian would not look for a root member called "Customers" in
>> > every dimension.
>> >
>> > 2. Specify root members in the schema. E.g.
>> >
>> > <Attribute name='Gender' ... >
>> >  <Members>
>> >   <Member key='F'/>
>> >   <Member key='M'/>
>> >  </Members>
>> > </Attribute>
>> >
>> > 3. Use aggregate tables to find level members. This proposal is flawed,
>> > because only 'non empty' members would come back. For example, if you asked
>> > for [Time].[Year].members, 2012 would not be returned from the agg table,
>> > because we have not yet made a sale in 2012. We would need a way to specify
>> > that this approximation is safe for a given level.
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