running number of a flow

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Shu Ting

• April 18, 2017 13:57

How do I create a running number of a data flow (similar to auto increment of database)?

Every time the data flow run, the number should be increased by a constant (i.e. 1), and will be emitted as one of the output columns.

Thanks.

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  Stony Smith

  • April 18, 2017 21:16

  use this:

  emit execCount as myRowNumber

  or this:

  if firstExec then myRowNumber=0
    myRowNumber = myRowNumber +1
  
  emit myRowNumber

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  Shu Ting

  • April 19, 2017 00:59

  Thank you. What if I want the number to be persistent per run not per row.

  For example, for initial run

  run_id, name, amount

  1, susan, 1000

  1, peter, 200

  1, Samie, 300

  Next time when the data flow is executed

  2, susan, 1212

  2, peter, 234

  2, Samie, 334

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  Adrian Williams

  • April 19, 2017 10:53

  There are probably some more elegant ways to achieve this but... the attached .lna file contains a node that stores a persistent execution count in the specified file. If the file does not exist it is created and the execution count starts at 1.

  Obviously, you must use a unique file for each data flow that would use a persistent execution counter.

  Regards,

  Adrian

   

  Attached files

  Persistent_Exec_Count.lna

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  Stony Smith

  • April 19, 2017 16:18

  Another possible way to do this is to use the date (and time) as a unique identifier

   

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