[Mondrian] need to get SQL queries from MDX

Luc Boudreau lucboudreau at gmail.com
Mon Feb 21 12:08:40 EST 2011


What you are trying to accomplish is more complex than you would expect.
Mondrian does not necessarily translate a given MDX query into a
deterministic list of SQL statements. Imagine the work load and poor
performance if this was the case. So for optimization reasons, Mondrian will
use a heuristic approach in order to figure out the most efficient way to
answer a given MDX query. The SQL queries will themselves be tailored to
take full advantage of the underlying RDBMS facilities. Mondrian will also
represent internally the data tuples / aggregations in a cross-query
reusable cache structure, so the order in which the MDX queries come in will
influence which SQL query get generated/executed.

As you can guess by now, it is a big requirement. There are also
architectural constraints we would require on possible contributions before
we accept to become the stewards of the code. Should you decide to go
forward, I strongly suggest we have an in-depth discussion about this
feature and how it fits in Mondrian as a whole.

Luc


On Mon, Feb 21, 2011 at 11:59 AM, JS Ubei <jsubei at yahoo.fr> wrote:

> Hi Luc,
>
> One more time, thank you.
> Wonderfull this feature ... but I can't wait !
>
> I will try to evaluate the difficulty to do this myself and if it's too
> hard or "time consumer" I will do my multidimensional database exploration
> without mondrian.
>
> And what the problem if I just, to begin, add a flag to know if I really
> want execute the query (i.e. fetch results) or if I just want the SQL query
> building part ?
>
>
>
> ------------------------------
> *De :* Luc Boudreau <lucboudreau at gmail.com>
> *À :* Mondrian developer mailing list <mondrian at pentaho.org>
> *Cc :* JS Ubei <jsubei at yahoo.fr>
> *Envoyé le :* Lun 21 février 2011, 13h 39min 31s
> *Objet :* Re: [Mondrian] need to get SQL queries from MDX
>
> Norbie,
>
> The feature you are searching for doesn't exist yet. But good news for you,
> it is on the roadmap for this year. We included it in a feature request
> called "Explain Query Feature". The end result will do exactly what you are
> looking for, and then more. Keep a watch on the following Jira case for
> updates. Should you decide to contribute to parts of this feature, don't
> hesitate to get in touch with us.
>
> http://jira.pentaho.com/browse/MONDRIAN-856
>
>
>
>
> On Mon, Feb 21, 2011 at 9:04 AM, JS Ubei <jsubei at yahoo.fr> wrote:
>
>> Dear mondrian community,
>>
>> In a starting project I plan to use mondrian for MDX queries facilitiy.
>> But in
>> another part of the project we need to have the SQL resulting queries to
>> use
>> with an external tool (GIS).
>> How can I do with the API ?
>> Idealy, something like :
>>
>> //********************
>> Query query = connection.parseQuery(...)
>> String sql_query = connection.getSQL(query)
>> //*******************
>>
>> Is the SqlStatement.execute() a good starting point to explore ?
>>
>> Best regards,
>> Norbie
>>
>>
>>
>> _______________________________________________
>> Mondrian mailing list
>> Mondrian at pentaho.org
>> http://lists.pentaho.org/mailman/listinfo/mondrian
>>
>
>
>
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