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Pig >> mail # dev >> Can someone explain the purpose UID serves in the logical plan?


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Can someone explain the purpose UID serves in the logical plan?
Howdy ya'll,

I'm trying to fix the issue in this JIRA:
https://issues.apache.org/jira/browse/PIG-3093

I got the plan at one point, as saw this:

#-----------------------------------------------

# New Logical Plan:

#-----------------------------------------------

D: (Name: LOForEach Schema: B::field1#4:chararray,field2#4:chararray)

|   |

|   (Name: LOGenerate[false,false] Schema:
B::field1#4:chararray,field2#4:chararray)

|   |   |

|   |   B::field1:(Name: Project Type: chararray Uid: 4 Input: 0 Column:
(*))

|   |   |

|   |   A::field1:(Name: Project Type: chararray Uid: 4 Input: 1 Column:
(*))

|   |

|   |---(Name: LOInnerLoad[B::field1] Schema: B::field1#4:chararray)

|   |

|   |---(Name: LOInnerLoad[A::field1] Schema: A::field1#4:chararray)

|

|---C: (Name: LOJoin(HASH) Schema:
A::field1#4:chararray,B::field1#4:chararray)

    |   |

    |   field1:(Name: Project Type: chararray Uid: 4 Input: 0 Column:
field1)

    |   |

    |   field1:(Name: Project Type: chararray Uid: 4 Input: 1 Column:
field1)

    |

    |---A: (Name: LOLoad Schema: field1#4:chararray)RequiredFields:null

    |

    |---B: (Name: LOForEach Schema: field1#4:chararray)

        |   |

        |   (Name: LOGenerate[false] Schema: field1#4:chararray)

        |   |   |

        |   |   field1:(Name: Project Type: chararray Uid: 4 Input: 0
Column: (*))

        |   |

        |   |---(Name: LOInnerLoad[0] Schema: field1#4:chararray)

        |

        |---A: (Name: LOLoad Schema: field1#4:chararray)RequiredFields:null
Noting that the Uid is repeated (because the 2 fields are derived from the
same field). I'm not sure if this is the source of the error, but since I
do not yet know what the error is I thought I would ask about it, as I do
not well understand the role of the uid, but it comes up a lot in the
LogicalPlan.
Thank you!

Jon