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Thread: Mapping

  1. #1
    Join Date
    Oct 2007
    Posts
    25

    Default Mapping

    Hey.

    The Mapping transformation used to create sub transformations waits for the stream to be completely loaded before starting or is fed immediatly with the rows that are arriving from the stream? I wanted to make the sub transformation start only with the complete set of data from the stream...

    Tks,
    Gustavo

  2. #2
    Join Date
    Oct 2007
    Posts
    25

    Default

    Anybody knows this?

    I appreciate if anybody clarifies me on this...

  3. #3
    Join Date
    Nov 1999
    Posts
    9,729

    Default

    A Mapping basically is a transformation on its own. As such, it will start running immediately.
    If you want it to wait for all rows you should use a temporary table and 2 separate transformations in a job.
    Alternatively, you can look at the "Blocking Step" in a recent PDI version that has the capability of caching all rows until the last one has arrived.
    (the "pass all rows" option)

    Matt

  4. #4
    Join Date
    Oct 2007
    Posts
    25

    Default

    Thank you Matt.

    The Blocking Step says it only passes the last row received to the next step? Maybe you're refering to 3.0. I'm on 2.5.2...

  5. #5
    Join Date
    Nov 1999
    Posts
    9,729

    Default

    Yes, so it seems. You could simulate the same behavior by using a Sort step.
    That being said I still think you should probably split up the transformation.

    You are probably trying to force some transactions or something and your mileage is going to vary.

    http://wiki.pentaho.org/display/EAI/...sked+Questions (How to sequentialize transformations in the "beginners" section)

    Matt

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