[Mondrian] SOLVE_ORDER: AS2K vs. SSAS2005

Matt Campbell mkambol at gmail.com
Thu Mar 27 16:29:42 EDT 2008


I've had a persistent headache over the past several months trying to deal
with solve order related issues.  We have limited control over the MDX
generated by our reporting tool (Cognos), which means that in some cases the
solve order of calculated members in the query is incorrect relative to the
solve order of cube members.

While this is a problem with Cognos, it is really a general issue with any
reporting client.  Since the client can't really guess what the solve order
of measures in the cube is, let alone what the user intends with a
particular calculation, there is always the possibility of conflict.  A tool
can allow specifying absolute solve order, but that means the user creating
the report needs to know and understand details about cube definition that
they may not have access to.

Recently I've learned more about how SSAS2005 handles solve order.  SSAS2005
uses a model where solve order is given a scope.  Members within the cube
are by default evaluated before members in the query, regardless of relative
solve order.  In almost all cases this makes better sense.  For the times
when it doesn't SSAS allows you to specify SCOPE_ISOLATION=CUBE for a
particular member to allow the AS2K behavior.  I did a write up of the
differences at
http://777eisenhower.blogspot.com/2008/03/analysis-services-2000-vs-2005.htmlif
anyone is interested.  The SSAS 2005 behavior seems like it would
eliminate most of the problems we've had.

Has anyone else run into similar problems with solve order?  I'm planning on
creating some unit tests which demonstrate the SSAS 2005 behavior, and
hopefully this can eventually be rolled into Mondrian.
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