java – 在级联中构建自定义连接逻辑,仅确保MAP_SIDE

解决这个问题的最好方法(我可以想到)是修改你的较小的数据集.您可以向较小的数据集添加新的字段(F1DecidingFactor). F1Result的价值可以如下：

Sudo代码

if F1DecidingFactor == "Yes" then
    F1Result = ACTUAL_VALUE
else
    F1Result = "N/A"

结果表

|F1#Join|F1#Result|F1#DecidingFactor|
|    Yes|        0|             True|
|    Yes|        1|            False|
|     No|        0|              N/A|
|     No|        1|              N/A|

您也可以通过级联进行上述操作.

之后,您可以进行地图侧的加入.

如果修改较小的数据集是不可能的,那么我有2个选项来解决问题.

选项1

将新的字段添加到您的小管道,这相当于您决定的因素(即F1DecidingFactor_RHS =是).然后将其包含在您的加入条件中.一旦你的加入完成,你将只有这些条件匹配的那些行的值.否则将为空/空白.示例代码：

主班

import cascading.operation.Insert;
import cascading.pipe.Each;
import cascading.pipe.HashJoin;
import cascading.pipe.Pipe;
import cascading.pipe.assembly.discard;
import cascading.pipe.joiner.LeftJoin;
import cascading.tuple.Fields;

public class StackHashJoinTestOption2 {
    public StackHashJoinTestOption2() {
        Fields f1Input = new Fields("F1Input");
        Fields f2Input = new Fields("F2Input");
        Fields f1Join = new Fields("F1Join");
        Fields f2Join = new Fields("F2Join");

        Fields f1DecidingFactor = new Fields("F1DecidingFactor");
        Fields f2DecidingFactor = new Fields("F2DecidingFactor");
        Fields f1DecidingFactorRhs = new Fields("F1DecidingFactor_RHS");
        Fields f2DecidingFactorRhs = new Fields("F2DecidingFactor_RHS");

        Fields lhsJoinerOne = f1DecidingFactor.append(f1Input);
        Fields lhsJoinerTwo = f2DecidingFactor.append(f2Input);

        Fields rhsJoinerOne = f1DecidingFactorRhs.append(f1Join);
        Fields rhsJoinerTwo = f2DecidingFactorRhs.append(f2Join);

        Fields functionFields = new Fields("F1DecidingFactor","F1Output","F2DecidingFactor","F2Output");

        // Large Pipe fields : 
        // F1DecidingFactor F1Input F2DecidingFactor F2Input
        Pipe largePipe = new Pipe("large-pipe");

        // Small Pipe 1 Fields : 
        // F1Join F1Result
        Pipe rhsOne = new Pipe("small-pipe-1");

        // New field to small pipe. Expected Fields:
        // F1Join F1Result F1DecidingFactor_RHS
        rhsOne = new Each(rhsOne,new Insert(f1DecidingFactorRhs,"Yes"),Fields.ALL);

        // Small Pipe 2 Fields : 
        // F2Join F2Result
        Pipe rhsTwo = new Pipe("small-pipe-2");

        // New field to small pipe. Expected Fields:
        // F2Join F2Result F2DecidingFactor_RHS
        rhsTwo = new Each(rhsTwo,Fields.ALL);

        // Joining first small pipe. Expected fields after join: 
        // F1DecidingFactor F1Input F2DecidingFactor F2Input F1Join F1Result F1DecidingFactor_RHS
        Pipe resultsOne = new HashJoin(largePipe,lhsJoinerOne,rhsOne,rhsJoinerOne,new LeftJoin());

        // Joining second small pipe. Expected fields after join: 
        // F1DecidingFactor F1Input F2DecidingFactor F2Input F1Join F1Result F1DecidingFactor_RHS F2Join F2Result F2DecidingFactor_RHS
        Pipe resultsTwo = new HashJoin(resultsOne,lhsJoinerTwo,rhsTwo,rhsJoinerTwo,new LeftJoin());

        Pipe result = new Each(resultsTwo,functionFields,new TestFunction(),Fields.REPLACE);

        result = new discard(result,f1DecidingFactorRhs);
        result = new discard(result,f2DecidingFactorRhs);

        // result Pipe should have expected result
    }
}

选项2

如果要使用默认值而不是null / blank,那么建议先使用默认的Joiners进行HashJoin,然后使用一个函数来更新具有适当值的元组.就像是：

主班

import cascading.pipe.Each;
import cascading.pipe.HashJoin;
import cascading.pipe.Pipe;
import cascading.pipe.joiner.LeftJoin;
import cascading.tuple.Fields;

public class StackHashJoinTest {
    public StackHashJointest() {
        Fields f1Input = new Fields("F1Input");
        Fields f2Input = new Fields("F2Input");
        Fields f1Join = new Fields("F1Join");
        Fields f2Join = new Fields("F2Join");

        Fields functionFields = new Fields("F1DecidingFactor","F2Output");

        // Large Pipe fields : 
        // F1DecidingFactor F1Input F2DecidingFactor F2Input
        Pipe largePipe = new Pipe("large-pipe");

        // Small Pipe 1 Fields : 
        // F1Join F1Result
        Pipe rhsOne = new Pipe("small-pipe-1");

        // Small Pipe 2 Fields : 
        // F2Join F2Result
        Pipe rhsTwo = new Pipe("small-pipe-2");

        // Joining first small pipe. 
        // Expected fields after join: 
        // F1DecidingFactor F1Input F2DecidingFactor F2Input F1Join F1Result
        Pipe resultsOne = new HashJoin(largePipe,f1Input,f1Join,new LeftJoin());

        // Joining second small pipe. 
        // Expected fields after join: 
        // F1DecidingFactor F1Input F2DecidingFactor F2Input F1Join F1Result F2Join F2Result
        Pipe resultsTwo = new HashJoin(resultsOne,f2Input,f2Join,Fields.REPLACE);

        // result Pipe should have expected result
    }
}

更新功能

import cascading.flow.FlowProcess;
import cascading.operation.BaSEOperation;
import cascading.operation.Function;
import cascading.operation.FunctionCall;
import cascading.tuple.Fields;
import cascading.tuple.TupleEntry;

public class TestFunction extends BaSEOperation<Void> implements Function<Void> {

    private static final long serialVersionUID = 1L;

    private static final String DECIDING_FACTOR = "No";
    private static final String DEFAULT_VALUE = "N/A";

    // Expected Fields: "F1DecidingFactor","F2Output"
    public TestFunction() {
        super(Fields.ARGS);
    }

    @Override
    public void operate(@SuppressWarnings("rawtypes") FlowProcess process,FunctionCall<Void> call) {
        TupleEntry arguments = call.getArguments();

        TupleEntry result = new TupleEntry(arguments);

        if (result.getString("F1DecidingFactor").equalsIgnoreCase(DECIDING_FACTOR)) {
            result.setString("F1Output",DEFAULT_VALUE);
        }

        if (result.getString("F2DecidingFactor").equalsIgnoreCase(DECIDING_FACTOR)) {
            result.setString("F2Output",DEFAULT_VALUE);
        }

        call.getoutputCollector().add(result);
    }

}

参考

> Insert Function
> Custom Function
> HashJoin

这应该可以解决你的问题.让我知道这是否有帮助.