[Mondrian] Multi-threading SQL execution

John V. Sichi jsichi at gmail.com
Fri Feb 9 05:53:07 EST 2007

michael bienstein wrote:
> The main issues I see are:
> 1) Either you let the database do the parallelism, in which case you 
> need to issue effectively multiple GROUP BYs in one SELECT (which is 
> possible on some databases such as ORACLE and even MySQL with its ROLLUP 
> option) and then disentangle the results,
> but this is not a standard in SQL.

Actually, SQL/OLAP (including CUBE, ROLLUP, and window clauses) is now 
standard in SQL:2003, but de facto, yeah, you can't rely on it as 
universal yet.

> In the options (2) and (3) you need to revisit the way JDBC connections 
> are handled by Mondrian.  In option (1) you need to maintain different 
> SQL generation strategies.  All nice ideas but a lot of work.  Yes I've 
> thought about it.  But who can do it?  Frustrating.

Long term, LucidEra will probably work on (1).  We're planning to start 
on subtotal calculated member pushdown first.  Once LucidDB 
(http://www.luciddb.org) can handle SQL/OLAP, we'll want Mondrian to 
generate it.


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