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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3033: [FLINK-5256] Extend DataSetSingleRowJoin to suppor...
Date Tue, 17 Jan 2017 14:39:03 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3033#discussion_r96419377
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/dataset/DataSetSingleRowJoin.scala
---
    @@ -144,21 +150,46 @@ class DataSetSingleRowJoin(
     
         val condition = codeGenerator.generateExpression(joinCondition)
     
    -    val joinMethodBody = s"""
    -                  |${condition.code}
    -                  |if (${condition.resultTerm}) {
    -                  |  ${conversion.code}
    -                  |  ${codeGenerator.collectorTerm}.collect(${conversion.resultTerm});
    -                  |}
    -                  |""".stripMargin
    +    val joinMethodBody =
    +      if (joinType == JoinRelType.INNER) {
    +        s"""
    +         |${condition.code}
    +         |if (${condition.resultTerm}) {
    +         |  ${conversion.code}
    +         |  ${codeGenerator.collectorTerm}.collect(${conversion.resultTerm});
    +         |}
    +         |""".stripMargin
    +    } else {
    +        val singleNode =
    +          if (leftIsSingle) {
    +            leftNode
    +          }
    +          else {
    +            rightNode
    +          }
    +        val notSuitedToCondition = singleNode
    +          .getRowType
    +          .getFieldList
    +          .map(field => getRowType.getFieldNames.indexOf(field.getName))
    +          .map(i => s"${conversion.resultTerm}.setField($i,null);")
    --- End diff --
    
    This only works if the result term is a `Row`. 
    
    It think a better approach is to generate a dedicated result expression for the null case
based on `CodeGenerator.generateResultExpression()`, where the field expressions are the outer
fields and the null expressions. Then we could use the current result expression if the condition
is met and the result expression with null values if that is not the case.
    
    We would need to extend the `CodeGenerator` with methods for `generateFieldAccesses(boolean
firstInput)` (see `generateConverterResultExpression()`) and `generateNullValues(boolean firstInput)`
which generates expressions for null values.


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