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Thread: Simple Evaluation step - I am getting The previous result is empty! in error log

  1. #1

    Default Simple Evaluation step - I am getting The previous result is empty! in error log

    Hi

    I think I did exactly as http://wiki.pentaho.com/display/EAI/...28Job+Entry%29 wiki said but I am getting this error.

    What in seven heavens could I have done wrong...sigh
    Attached Files Attached Files

  2. #2
    Join Date
    Jul 2009
    Posts
    476

    Default

    Instead of the SQL step in your job, use an "Evaluate rows number in a table" step, and check the "Add rows to result" checkbox.

  3. #3
    Join Date
    Jun 2012
    Posts
    5,534

    Default

    Just some additional comments on your attached files:

    • The SQL entry will ignore any query results, not so the Table Input transformation step
    • Instead of an absolute file path you can use a variable, e.g. ${Internal.Transformation.Filename.Directory}
    • When referring to a previous result, you should have created one before
    • You can't copy rows to the result stream in a transformation, before you created them in that very transformation
    • If you find yourself having a hard time arranging your design, try Tools/Options.../Look&Feel/Grid Size = 16
    So long, and thanks for all the fish.

  4. #4

    Default

    Thanks to marabou and robj. I am still in draft phase getting familiar with the tool.

    I just have hard time finding good samples of controlling workflows. As a data analyst I have little experience of procedural programming - I try to write SQL to solve problems as I used to do

    I find lookups, joins, analytical queries, group by-s etc familiar animals but how to control workflow in Pentaho is really obscure to me. I used to do this with temporary tables, log tables, control tables...It is hard to understand what "piece" is meant for what.

  5. #5
    Join Date
    Apr 2008
    Posts
    1,771

    Default

    Hi JoyDivision,
    I had the same problem!

    My approach is to split the whole process in small parts.
    Then I try to create transformations (group of steps) for each small part.
    Finally I put them together using jobs.

    Exceptions!
    - since all steps within a transformation are initialised at the same time, sometime you need to split a part in further transformations
    - if you create variables, you need at least 2 transformations and 1 job
    - if you need to process a list of files one at the time

    Hope this helps.
    Mick

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