[Mondrian] performance impact of having several cross joins of dimensions at the All level

Robin Tharappel rtharappel at prospricing.com
Wed Aug 29 21:25:16 EDT 2007



We have observed a significant slow down in performance when the there
are several nested NonEmptyCrossJoin calls in an MDX query. Below is an
example query that shows the non empty cross join of about 40
dimensions, however only 3 dimensions are not at the All level ( Dim18,
Dim20, and Dim28). We see a substantial improvement in performance when
the dimensions at the All level are removed. The performance impact
appears to be in lower CPU utilization for Mondrian. Since the other
dimensions are at the All level the expectation is that not much
processing would not be required for them. What is the overhead incurred
for a dimension at the All level in this case ? 


WITH SET [#DataSet#] as
(NonEmptyCrossjoin(NonEmptyCrossjoin({[Dim1].[All]}, {[Dim2].[All]}),
{[Dim3].[All]}), {[Dim4].[All]}), {[Dim5].[All]}), {[Dim6].[All]}),
{[Dim7].[All]}), {[Dim8].[All]}), {[Dim9].[All]}), {[Dim10].[All]}),
{[Dim11].[All]}), {[Dim12].[All]}), {[Dim13].[All]}), {[Dim14].[All]}),
{[Dim15].[All]}), {[Dim16].[All]}), {[Dim17].[All]}),
{Descendants([Dim18].[All], 3)}), {[Dim19].[All]}),
{[Dim20].[All].Children}), {[Dim21].[All]}), {[Dim22].[All]}),
{[Dim23].[All]}), {[Dim24].[All]}), {[Dim25].[All]}), {[Dim26].[All]}),
{[Dim27].[All]}), {Descendants([Dim28].[All], 3)}), {[Dim29].[All]}),
{[Dim30].[All]}), {[Dim31].[All]}), {[Dim32].[All]}), {[Dim33].[All]}),
{[Dim34].[All]}), {[Dim35].[All]}), {[Dim36].[All]}), {[Dim37].[All]}),
{[Dim38].[All]}), {[Dim39].[All]}), {[Dim40].[All]}), {[Dim41].[All]}),
{[Dim42].[All]}), {[Dim43].[All]})' SELECT {[Measures].[Measure1],
[Measures].[Measure2], [Measures].[Measure3]} on columns, NON EMPTY
Hierarchize({[#DataSet#]}) on rows FROM [Transaction]






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