An Insight into ASO MDX Execution

If you’re familiar with Dan Pressman’s work on ASO internals, you’ll know that he sometimes talks about the number of “bitmap passes” required to answer a particular MDX query.  I don’t want to rehash everything Dan says here, but the following Kscope 2014  presentation (free “associate membership” required) contains a good explanation: How ASO Works and How to Design for Performance.  Dan’s chapter in “Developing Essbase Applications” touches on the same concepts.

In brief, what Dan says is that a given MDX query may require Essbase to run one or more “stored queries” under the hood.  He makes a pretty convincing case, using the analysis to show why (for example) a stacked hierarchy provides better query performance than pure MDX to calculate YTD.  However, I don’t think anyone has pointed out that MaxL exposes a measure that helps prove that this is really what happens: “kernel_queries_tracked”. Continue reading