In the 2 previous blog entries about recreating the SSAS example cubes for Adventure Works sales BI on Pentaho, I focused on generating new departmental-sized ROLAP cubes through the thin client Auto Modeler tools here & here.
In this entry, I’m going to show you how you can move over to the Pentaho BA Suite quickly by getting started with your existing SSAS cubes, such as the Adventure Works sales cubes, by migrating them pretty much as-is to the Pentaho ROLAP engine called Mondrian. This way, you can use the modeling tools that you are already familiar with (i.e. BIDS) and just convert them to Mondrian. Once you are converted over to the Pentaho platform, then you can start playing around with Pentaho analytics and manage the new version of the cubes in Pentaho.
In case you didn’t already do so, make sure you go here to download the evaluation of the Pentaho Business Suite here. And here is the Codeplex link for the open source download of the Adventure Works SSAS 2012 MOLAP cubes that we’ll use for this demonstration.
Make sure you also download the SQL Server 2012 JDBC driver and the tool that I built to help you migrate your online SSAS cubes from the SQL Server Analysis Server to Mondrian XML schema output files using AMO here, called SSAS2MONDRIAN. The full source code and C# project is available on GitHub in case you want to add more to it, have a look around, etc. The tool needs more features and error catching, so please contribute your ideas back to the source project!
So basically, instead of recreating a new OLAP model in Pentaho’s Analyzer, we are going to just migrate as-is from SSAS. Instead of rewriting the details of some of the primary differences between the 2 engines that you need to be aware of, I’m going to just link you back to my last posting on this topic at KromerBigData. You’ll need to become familiar with the Mondrian schema and MDX differences because we don’t have a complete migration tool that can do it all for you. Instead, the ssas2mondrian utility will take your model outline of dimensions, measures, expressions, attributes, hierarchies and measure groups and convert them to Mondrian descriptors and names, but leaving out decisions about conflicts and conversion gaps in the hands of the BI developer.
Ok, once you’ve loaded the AdventureWorks 2012 DW database and the MOLAP cubes from Codeplex into SQL Server, you should see them appear in your SSMS:
Next, run the ssas2mondrian utility and redirect the output to an XML file so that we’ll be able to open the model in Pentaho Schema Workbench to make it ready for Mondrian:
You can see some of the output in that PowerShell screenshot above. I first ran the conversion utility without redirecting the output to a file, so some of the stdout is visible. I selected the server, cube, SSAS databsae and chose a new name for the resulting Mondrian schema, which is what will appear to report users when they build reports in Pentaho Analyzer.
Notice the conversion utility just using Console.WriteLine to output a Mondrian schema format. But, now I can open that schema file in Pentaho Schema Workbench (PSW) and work with it to clean things up and make it ready for Pentaho Analytics:
Make sure that you connect to the AdventureWorksDW2012 database from PSW as well under Database Connections. Remember that Mondrian is ROLAP only, so you will always send queries to the source database in Mondrian which will handle caching as well. Also take notice of the red check marks above. That means that you’ll want to open those nodes in the tree and look at the error in the bottom of the PSW screen. It is possible that some of the table names are actually named queries in the SSAS cube model, which means that those will need to become views in the source Adventure Works database to resolve the red check in PSW for Mondrian.
You can now use that ROLAP model to build Pentaho Analyzer reports and continue to maintain the models directly in Pentaho Mondrian, taking SSAS away from the solution. Or, if you like designing models in BIDS, build your cube there and then run ssas2mondrian to load the model into the Pentaho suite!