Examples of cascading.operation.aggregator.First

cascading.operation.aggregator.First
Class First is an {@link Aggregator} that returns the first {@link Tuple} encountered in a grouping.
By default, it returns the first Tuple of {@link Fields#ARGS} found.
If {@code firstN} is given, Tuples with each of the first N number of Tuples encountered are returned. That is,this Aggregator will return at maximum N tuples per grouping.
Be sure to set the {@link cascading.pipe.GroupBy} {@code sortFields} to control which Tuples are seen first.


    Function splitter = new RegexSplitter( new Fields( "num", "char" ), " " );


    Pipe pipeLower = new Each( new Pipe( "lower" ), new Fields( "line" ), splitter );
    pipeLower = new GroupBy( pipeLower, new Fields( "num" ) );
    pipeLower = new Every( pipeLower, new Fields( "char" ), new First(), Fields.ALL );


    Pipe pipeUpper = new Each( new Pipe( "upper" ), new Fields( "line" ), splitter );
    pipeUpper = new GroupBy( pipeUpper, new Fields( "num" ) );
    pipeUpper = new Every( pipeUpper, new Fields( "char" ), new First(), Fields.ALL );


    Pipe splice = new CoGroup( pipeLower, new Fields( "num" ), pipeUpper, new Fields( "num" ), Fields.size( 4 ) );


    Flow flow = getPlatform().getFlowConnector().connect( sources, sink, splice );

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    Function splitter1 = new RegexSplitter( new Fields( "num1", "char1" ), " " );


    Pipe pipeLower = new Each( new Pipe( "lower" ), new Fields( "line" ), splitter1 );
    pipeLower = new Each( pipeLower, new Insert( new Fields( "one", "two", "three", "four" ), "one", "two", "three", "four" ), Fields.ALL );
    pipeLower = new GroupBy( pipeLower, new Fields( "num1" ) );
    pipeLower = new Every( pipeLower, new Fields( "char1" ), new First(), Fields.ALL );


    Function splitter2 = new RegexSplitter( new Fields( "num2", "char2" ), " " );


    Pipe pipeUpper = new Each( new Pipe( "upper" ), new Fields( "line" ), splitter2 );
    pipeUpper = new GroupBy( pipeUpper, new Fields( "num2" ) );
    pipeUpper = new Every( pipeUpper, new Fields( "char2" ), new First(), Fields.ALL );


    Pipe splice = new CoGroup( pipeLower, new Fields( "num1" ), pipeUpper, new Fields( "num2" ) );


    Flow flow = getPlatform().getFlowConnector().connect( sources, sink, splice );

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    uniques = new Each( uniques, new Fields( "line" ), new RegexSplitGenerator( new Fields( "word" ), "\\s" ) );


    uniques = new GroupBy( uniques, new Fields( "word" ) );


    uniques = new Every( uniques, new Fields( "word" ), new First( Fields.ARGS ), Fields.REPLACE );


//    uniques = new Each( uniques, new Debug( true ) );


    Pipe fielded = new Pipe( "fielded" );

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    Pipe pipeUpper = new Each( new Pipe( "upper" ), new Fields( "line" ), splitter );
    Pipe pipeOffset = new Each( new Pipe( "offset" ), new Fields( "line" ), splitter );


    Pipe splice = new GroupBy( "merge", Pipe.pipes( pipeLower, pipeUpper, pipeOffset ), new Fields( "num" ), new Fields( "char" ) );


    splice = new Every( splice, new Fields( "char" ), new First( new Fields( "first" ) ) );


    splice = new Each( splice, new Fields( "num", "first" ), new Identity() );


    Flow flow = getPlatform().getFlowConnector().connect( sources, sink, splice );

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    pipe = new Each( pipe, new SortElements( new Fields( "n1", "v1" ), new Fields( "n2", "v2" ) ) );


    // unique the pipe
    pipe = new GroupBy( pipe, Fields.ALL );


    pipe = new Every( pipe, Fields.ALL, new First(), Fields.RESULTS );


    // out: name1, name2, movie, name1, rate1, name2, rate2
    pipe = new GroupBy( pipe, new Fields( "n1", "n2" ) );


    // out: movie, name1, rate1, name2, rate2, score

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    Function splitter = new RegexSplitter( new Fields( "num", "char" ), " " );


    Pipe pipeLower = new Each( new Pipe( "lower" ), new Fields( "line" ), splitter );
    pipeLower = new GroupBy( pipeLower, new Fields( "num" ) );
    pipeLower = new Every( pipeLower, new Fields( "char" ), new First(), Fields.ALL );


    Pipe pipeUpper = new Each( new Pipe( "upper" ), new Fields( "line" ), splitter );
    pipeUpper = new GroupBy( pipeUpper, new Fields( "num" ) );
    pipeUpper = new Every( pipeUpper, new Fields( "char" ), new First(), Fields.ALL );


    Pipe splice = new HashJoin( pipeLower, new Fields( "num" ), pipeUpper, new Fields( "num" ), Fields.size( 4 ) );


    Flow flow = getPlatform().getFlowConnector().connect( sources, sink, splice );

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    Pipe pipeLower = new Each( new Pipe( "lower" ), new Fields( "line" ), splitter );
    Pipe pipeUpper = new Each( new Pipe( "upper" ), new Fields( "line" ), splitter );


    Pipe splice = new CoGroup( pipeLower, new Fields( "num" ), pipeUpper, new Fields( "num" ), new Fields( "num1", "lhs", "num2", "rhs" ) );


    splice = new Every( splice, new First( new Fields( "value" ) ), new Fields( "num1", "value" ) );


    Flow countFlow = getPlatform().getFlowConnector().connect( sources, sink, splice );
    }

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    Pipe pipeLower = new Each( new Pipe( "lower" ), new Fields( "line" ), splitter );
    Pipe pipeUpper = new Each( new Pipe( "upper" ), new Fields( "line" ), splitter );


    Pipe splice = new CoGroup( pipeLower, new Fields( "num" ), pipeUpper, new Fields( "num" ), new Fields( "num1", "lhs", "num2", "rhs" ), new Fields( "somenum", "somenum2" ) );


    splice = new Every( splice, new First( new Fields( "value" ) ), new Fields( "somenum", "value" ) );


    Flow countFlow = getPlatform().getFlowConnector().connect( sources, sink, splice );
    }

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    pipe = new Each( pipe, new SortElements( new Fields( "name1", "rate1" ), new Fields( "name2", "rate2" ) ) );


    // unique the pipe
    pipe = new GroupBy( pipe, Fields.ALL );


    pipe = new Every( pipe, Fields.ALL, new First(), Fields.RESULTS );


    // calculate square of diff
    Function sqDiff = new Identity( new Fields( "score" ) )
    {
    public void operate( FlowProcess flowProcess, FunctionCall functionCall )

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      pipe = new Each( pipe, new Identity() );


      pipe = new GroupBy( pipe, Fields.ALL );


      pipe = new Every( pipe, new First(), Fields.RESULTS );


      setTails( pipe );
      }

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