[Mondrian] Calculated Member Solve Order & AggregateFunctionHandling

Matt Campbell mkambol at gmail.com
Tue May 20 08:49:50 EDT 2008


I think it should be the default behavior.  It doesn't seem like an MDX
client should usually need to know anything about the solve order of cube
defined calculated members.  In the AS2K world there was always the
possibility of unintended conflict just because the client didn't know how
cube solve orders happened to be set.

On Mon, May 19, 2008 at 8:39 PM, Julian Hyde <jhyde at pentaho.com> wrote:

>  Timothy,
>
> The change looks good, but you need to tie up a few loose ends to be tied
> up before I can accept the contribution:
>
> 1. The unit test cases need some work. I enabled the tests in
> SolveOrderScopeIsolationTest, and most worked if I preceded them with
> a check that SolveOrderMode==scoped. But
> testOverrideOverCubeMemberHappensWithScopeIsolation still gives errors;
> can't figure out whether it's to do with case sensitivity.
>
> And, can you create some cases that test the behavior when
> SolveOrderMode==absolute. This will be especially important when scoped
> becomes the default behavior. Maybe make each test case into an 'if ...
> else' with alternative outputs.
>
> 2. The description of the property in mondrian.properties and
> MondrianProperties.java needs a little more information, because the average
> DBA would not know what SS2K behavior was (or SS2K was, for that matter).
> The information in your email below would do just fine.
>
> 3. Please put the same property information into configuration.html.
>
> 4. For future changes, please keep those lines to 80 characters, and use
> <p> to delimit paragraphs in javadoc.
>
> See attached a new change list with my modifications.
>
> All,
>
> Any opinions what should be the default behavior? I'm inclined to think
> that mondrian should use scoped solve-order (like Analysis Services 2005) by
> default.
>
> Julian
>
>  ------------------------------
> *From:* mondrian-bounces at pentaho.org [mailto:mondrian-bounces at pentaho.org]
> *On Behalf Of *timothy.lambert at thomsonreuters.com
> *Sent:* Monday, May 12, 2008 12:08 PM
> *To:* mondrian at pentaho.org
> *Subject:* [Mondrian] Calculated Member Solve Order &
> AggregateFunctionHandling
>
>  Sorry folks … hopefully this third time will be charmed.
>
>
>
> This time with a subject **and** the code attachment.
>
>
>  ------------------------------
>
> *From:* mondrian-bounces at pentaho.org [mailto:mondrian-bounces at pentaho.org]
> *On Behalf Of *Lambert, Timothy
> *Sent:* Monday, May 12, 2008 3:05 PM
> *To:* mondrian at pentaho.org
> *Subject:* [Mondrian] Calculated Member Solve Order & Aggregate
> FunctionHandling
>
>
>
> *Calculated Member Solve Order & Aggregate Function Handling *
>
> *SSAS2005 vs. SSAS2000 vs. Mondrian*
>
>
>
> *Background*
>
>
>
> This proposal was seeded by the R&D of others.
>
>
>
> Following are links to some of that work…
>
>
>
> http://forums.pentaho.org/showthread.php?t=60654
>
>
>
>
> http://777eisenhower.blogspot.com/2008/03/analysis-services-2000-vs-2005.html
>
>
>
> * *
>
> *SOLVE_ORDER Calculated Member Property*
>
>
>
> Definition:  The order of evaluation (from highest to lowest solve order)
> and calculation (from lowest to highest solve order) for calculated members,
> custom members, custom rollup formulas, and calculated cells in a single
> calculation pass of a multidimensional cube. Solve order is used to
> determine formula precedence when calculating values for cells in
> multidimensional cubes, but only within a single calculation pass.
>
>
>
> SSAS2000 Behavior:  The SOLVE_ORDER value is absolute regardless of where
> it is defined; e.g. a query defined calculated member with a SOLVE_ORDER of
> 1 always takes precedence over a cube defined value of 2.
>
>
>
> SSAS2005 Behavior:  By default, cube calculated members are resolved before
> any session scope calculated members, and session scope members are resolved
> before any query defined calculation.  The SOLVE_ORDER value only applies
> within the scope in which it was defined.
>
>
>
> Achieving SSAS2000 Behavior on SSAS2005:  Using the SCOPE_ISOLATION=CUBE
> property in a query calculated member definition will put the query defined
> member into cube scope.  So effectively solve_order is treated like an
> SSAS2000 absolute value since all members are treated as if they were
> defined in the same scope.
>
>
>
> *Aggregate Function*
>
>
>
> Definition:  Returns a number that is calculated by aggregating over the
> cells returned by the set expression.
>
>
>
> The Aggregation function is designed to be used against base measures.
>
>
>
> SSAS2000 Behavior:  The SOLVE_ORDER value must be manually applied such
> that aggregate values are solved before other related calculated members.
>
>
>
> SSAS2005 Behavior:  The aggregate function is always applied to base
> members; i.e. as if solve_order was defined to be the lowest value in a
> given evaluation in a SSAS2000 sense.
>
>
>
> *Current Mondrian Behavior*
>
> * *
>
> In regard to solve_order and Aggregate function handling, Mondrian behaves
> like SSAS2000.
>
>
>
> During the evaluation of a given cell, if there are multiple calculated
> members in the evaluation context then the member with the highest
> solve_order is evaluated.  The other calculated members with lower
> solve_order values stay within the evaluation context, and are evaluated
> during the processing of the calculated member with the higher solve_order.
>
>
>
> Through this recursive process, the calculated members with lower
> solve_order values get calculated before those with higher values.
>
>
>
>
>
> *Mondrian Issue*
>
> * *
>
> For use with certain reporting clients (e.g. Cognos), it is better for
> Mondrian to behave like SSAS2005 rather than SSAS2000 in regard to solve
> order and aggregate function evaluation.
>
>
>
> Note that some reporting clients (e.g. Cognos) do not take advantage of the
> SSAS2005 SCOPE_ISOLATION property, so support for it is not considered
> critically important.
>
>
>
> *Proposed Mondrian Changes*
>
>
>
> *High Level*
>
>
>
> The proposal involves enhancing Mondrian to optionally behave like SSAS2005
> rather than SSAS2000 in regard to solve order.
>
>
>
> The option is controlled using the MondrianProperties entry S
> olveOrderMode=absolute|scoped.  The current Mondrian solve order behavior
> remains the default; 'absolute'.  The SSAS2005 behavior can be turned on
> with the value of 'scoped'.  One can achieve SSAS2005 SCOPE_ISOLATION=CUBE
> semantics by using 'absolute' mode.
>
>
>
> While preserving old behavior as a default is usually desirable, in this
> case it is recommended that Mondrian adopt the SSAS2005 behavior as the
> default.
>
>
>
> The implementation of the proposal is based on the same sort of logic one
> uses when manually applying the solve_order property to get the desired
> SSAS2005-like behavior with current Mondrian.
>
>
>
> The 'scoped' solve order mode code determines the highest solve order based
> on…
>
>
> -   If the calculated member is involved with an aggregate function.
>
> Aggregation function based calculations are calculated first.
>
> -   The location of the calculated member definition; i.e. its scope.
>
> Cube scope members are calculated after Aggregate function based
> calculations.
>
> Query scope members are calculated after cube scope calculations.
>
> -   The solve_order property.
>
> This property is only used to order calculations within a given scope.
>
>
>
> * *
>
> *Code Changes*
>
>
>
> Attached to this email – the archive was built with the packChange script.
>
>
>
> The RolapEvaluator.peekCalcMember method now invokes one of two methods for
> determining the highest solve order for two or more calculated members.
> One of these methods implements the "absolute" algorithm and the other
> implements the "scoped" algorithm.
>
>
>
> Determining cube and query scope is easy since there is an already defined
> class method for determining if a member is defined in a query.  If it's not
> defined in the query then it must be defined in the cube.
>
>
>
> Determining relative solve_order is also trivial since that property is
> readily available for a given calculated member.
>
>
>
> Determining if the member is part of an aggregate function is a little more
> difficult.  There are (at least) two ways to go about this.
>
>
>
> In the proposed solution, there is a new RolapEvaluator method that
> traverses the expression graph associated with a calculated member
> explicitly looking for an aggregate function.
>
>
>
> An alternate solution performed a full evaluation of the calculated member
> in order to look for an aggregate function.  After the evaluation, a flag
> was checked to see if an aggregate function was found.
>
>
>
> * *
>
> *Unit Tests*
>
> * *
>
> A JUnit test (SolveOrderScopeIsolationTest) was recently contributed to the
> Mondrian project.  These test cases expect AS2005 behavior and as such fail
> with the current Mondrian.  So this test is not normally setup to run with
> the regular regression suite.
>
>
>
> When this test is enabled, the proposed implementation with the new AS2005
> solve order behavior passes all test cases.
>
>
>
> Note there is one exception in which Mondrian fails regardless of
> SolveOrderMode.  There seems to be an MDX syntax problem in one of the test
> cases.
>
>
>
> Also note there is one test case that passes for both the old and new
> behavior.
>
>
>
> There is another test case that passes for current Mondrian but fails for
> the new solve order behavior.  The test case is
> Mondrian.test.NamedSetTest.testOrderedNamedSet.  The test case explicitly
> expects SSAS2000 behavior and as such should fail with the new AS2005
> behavior.
>
>
>
>
> _______________________________________________
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>
>
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