[Mondrian] Making Pre-aggregated Tables Work

Luc Boudreau lucboudreau at gmail.com
Mon Apr 4 10:58:16 EDT 2016


> 1. Why does mondrian rely on the rowCount (...)

The number of rows tells us which of the aggregate tables is the most
efficient. There is not always a 1:1 match between a query's aggregation
level and the aggregation table's. When faced with two aggregation table
choices, both needing a supplemental grouping, the most efficient is the
one with the least rows.

> 2. Why does the code check if the aggregate table has more number of rows
than the fact table

Same as above. If an aggregation table is bigger than your fact table, then
you're better off using the fact table.


On Mon, Apr 4, 2016 at 10:24 AM, Tom Barber <tom at analytical-labs.com> wrote:

> On top of Amits questions, here's a bunch more output:
>
> We have 2 schema:
>
> http://pastebin.com/XkPSFN3P and http://pastebin.com/YbANX0pB
>
> The foodmart one uses the aggregate tables, the phoenix one doesn't.
>
> I've not been able to devote loads of time to debugging it, but Amit has
> been trying his best and we've been playing around with making sure phoenix
> uses a stats provider etc, and still it picks the fact table over the
> aggregate.
>
> http://pastebin.com/raw/MU6Xkqtk here's the mondrian logging output.
>
> Cheers
>
> Tom
>
> --------------
>
> Director Meteorite.bi - Saiku Analytics Founder
> Tel: +44(0)5603641316
>
> (Thanks to the Saiku community we reached our Kickstart
> <http://kickstarter.com/projects/2117053714/saiku-reporting-interactive-report-designer/>
> goal, but you can always help by sponsoring the project
> <http://www.meteorite.bi/products/saiku/sponsorship>)
>
> On 2 April 2016 at 11:10, Amit Shah <amits.84 at gmail.com> wrote:
>
>> Any inputs here? I'm sure having pre-aggregated tables must be a pretty
>> common practice.
>> I'm kind of blocked with this not working.
>>
>> Thanks,
>> Amit.
>>
>> On Fri, Apr 1, 2016 at 5:34 PM, Tom Barber <tom at analytical-labs.com>
>> wrote:
>>
>>> I'll extend this post slightly to add:
>>>
>>> We've enabled aggregates in mondrian.properties, and we added a
>>> Aggregate only measure and using that one forced the use of the aggregate
>>> table, so the aggregates are being parsed.
>>>
>>> --------------
>>>
>>> Director Meteorite.bi - Saiku Analytics Founder
>>> Tel: +44(0)5603641316
>>>
>>> (Thanks to the Saiku community we reached our Kickstart
>>> <http://kickstarter.com/projects/2117053714/saiku-reporting-interactive-report-designer/>
>>> goal, but you can always help by sponsoring the project
>>> <http://www.meteorite.bi/products/saiku/sponsorship>)
>>>
>>> On 1 April 2016 at 12:59, Amit Shah <amits.84 at gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> I have been using Mondrian 4 with Saiku as an OLAP engine. Mondrian is
>>>> integrated with apache phoenix (version 4.6) as the data source that used
>>>> apache hbase as the data store. In order to speed up the queries I am
>>>> trying to make pre-aggregated tables work but for some reason the actual
>>>> fact table is getting queried. Here's how the mondrian schema definition
>>>> looks like - http://pastebin.com/xquutKYX.
>>>>
>>>> The database schema for the dimension, facts and the pre-aggregated
>>>> table is shared here - http://pastebin.com/EWhyNLTJ
>>>>
>>>> Selecting the total sales measure and the agent id as a row in the
>>>> saiku builds up a query and tries to execute it on the facts table instead
>>>> of the pre-aggregated table. The query from the sql logs is
>>>>
>>>> DEBUG [mondrian.sql] 850: Segment.load: executing sql [select
>>>> "AGENTS"."A_ID" as "c0", sum("TRANSACTIONS"."TOTAL_SALES") as "m0" from
>>>> "TRANSACTIONS" as "TRANSACTIONS", "AGENTS" as "AGENTS" where
>>>> "TRANSACTIONS"."AGENT_ID" = "AGENTS"."A_ID" group by "AGENTS"."A_ID"]
>>>>
>>>> What could be missing in order to make the OLAP engine to use the
>>>> AG_TER_PRO (pre-aggregated table)?
>>>>
>>>> Thanks,
>>>> Amit.
>>>>
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>>>>
>>>>
>>>
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