In the previous parts (1, 2) I showed how to connect Informatica with MS-OLAP, meaning that a mapplet can process cube or dimension. The thing is that I focused on the side of MS-OLAP. In the second part I even wrote the T-SQL code itself. Now I want to close the loop by describing what's going on in the Informatica side. This part was made by my friend, Alex, who permitted me to post here about what he did.
First of all, there's a table which contains the parameters to call with to the MS-OLAP procedure (object id, type, user name, etc.). This table is the source (& source qualifier, of course) of the mapplet. Each row in this table calls the stored procedure in the MS-OLAP side (in fact, the procedure is part of the relational DB, but never mind now). The call to the SP is made with Informatica's Procedure block. The connection is a regular ODBC connection, as mentioned in the previous part. Now for the interesting part: In the mapplet, the result of the procedure (zero for success, one for failure) goes into a Java Transformation block. This java block will fail the mapplet if one or more procedure calls returned failure.
How to do this java block? Double click on it to enter its properties. Go to the "Java Code" tab. There you'll see tab for every event in this block's life cycle. Here is the code for every tab (only the relevant ones):
Helper Code:
static int errorCounter = 0;
static Object lock = new Object();
On Input Row:
if (returnValue != 0)
{
synchronized(lock)
{
errorCounter++;
}
}
On End of Data:
synchronized(lock)
{
if (errorCounter > 0)
{
failSession("OLAP Objects failed");
}
}
Note that:
- I'm not sure that the lock mechanism is required here. sync, lock, semaphore, etc. mechanisms are often used when atomic write is needed in order to solve problems like deadlocks, mutual write, etc. Here I simply don't care. Even if two parallel threads will read the errorCounter as zero and they both will increase it to one (when in fact it needs to have the value of two) it won't be a bug because the session will fail anyway. Alex & I need to talk about this point...
- failSession is a function which is part of Informatica's API. As you might guess, it will fail the whole mapplet.
- Very important: Calling all the MS-OLAP objects at once will cause an error in the Analysis Services server and all the objects will be in the state of Unprocessed. The Informatica side has to call the dimensions first and only then the cubes. The cubes must not be called all at once if they have relationships between them. This will cause deadlock too.