Alberto Ferrari
sqlbi.com
Alberto started working with SQL Server in 2000 and immediately his interest focused on Business Intelligence. He and Marco Russo created sqlbi.com, where they publish extensive content about Business Intelligence.
SQLBits 2013
DAX Query Engine Internals
In this session, we will analyze the way DAX solves filtering. Starting from simple queries, we will follow the steps DAX does with the filter context, discovering the internals of the query engine of DAX.
The VertiPaq engine, which is the core of
the new SQL Server Analysis Services Tabular engine, has an unprecedented level
of performance, thanks to its fine-tuned architecture and its ability to
perform fast cross-fltering. Automatic cross filtering between columns of the
same table or related tables is a very powerful feature of DAX. It allows a measure
to evaluate to different values for different cells in a pivot table even
though the DAX expression for the measure does not change. Filter context is
the underlying mechanism that enables this magic behavior. But it is also a
very tricky concept that even befuddles some DAX experts. In this session, we will
analyze the way DAX solves filtering. Starting from simple queries, we will
follow the steps DAX does with the filter context, discovering the internals of
the query engine of DAX.