#BWonHANA: OLAP Compiler Demo

Thomas Zurek

Posted by Thomas Zurek on May 13, 2013

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This video provides two examples that show the power of the OLAP compiler in BW-on-HANA.

Example 1

The first example basically pushes down the rowset to cellset conversion: the columns Quantity Jan, Quantity Jan-Feb and Quantity Jan-Mar have overlapping filter conditions, namely {Jan} ⊂ {Jan,Feb} ⊂ {Jan,Feb,Mar}. This means that a record X providing an aggregated value for Quantity will contribute in all the three columns if X has data from January. Or in other words: X appears in the rowset and needs to contribute into multiple cells of the cellset based result.

Example 2

The second example has a COUNT DISTINCT based key figure as an instance of an exception aggregation. The latter means that the aggregation function is bound to a specific (or exceptional) characteristic, namely orders in this instance. To calculate that function, all the orders need to be looked at, duplicates eliminated, to then be counted. This requires to list all the orders and this list can be long. In the demo, there are 1.343.674 orders.

Example 1: Multiple Complex Selections (Filters) Example 2: COUNT DISTINCT (exception aggregation)
Example 1: Multiple Complex Selections (Filters) Example 2: COUNT DISTINCT (exception aggregation)

Each example is processed in two different ways, the standard way (also in HANA) and the optimised way as explained by the blog:

  • The respective query on the left-hand side shows the standard processing via SQL [to HANA] and OLAP processing in the application server. This is the reason for much more records being transferred from HANA to the application server.
  • The respective query on the right-hand side shows the optimized processing via HANA’s calculation engine. The leads to less data being transferred to the application server as all aggregation are calculated inside HANA.

Here is the 1-min demo video on YouTube. I recommend that you switch the video quality to HD.

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