Question about type cast in ExpressionReducer's reduce procedure

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Question about type cast in ExpressionReducer's reduce procedure

郭健
Hi all,
            I am implementing a STR_TO_DATE scalar SQL function to flink, and found return type casted from java.sql.Date to Integer in Flink’s ExpressionReducer:
https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/ExpressionReducer.scala#L56

// we need to cast here for RexBuilder.makeLiteral


      case (SqlTypeName.DATE, e) =>


        Some(


          rexBuilder.makeCast(typeFactory.createTypeFromTypeInfo(BasicTypeInfo.INT_TYPE_INFO), e)


        )



            so str_to_date('01,5,2013','%d,%m,%Y')" must return an Integer, which conflicted with my implementation.

            My question is: why should we do this? I have seen in comments the reason to do this here is: “we need to cast here for RexBuilder.makeLiteral”, But is it reasonale to change user function’s return Type? Should we restore the origin return type after the reduce?


Thanks,
Aegeaner


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Re: Question about type cast in ExpressionReducer's reduce procedure

Jark Wu
Hi Aegeaner,

First of all, the ExpressionReducer actually restores the origin return
type after reducing, see
https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/ExpressionReducer.scala#L122

So the reduced result and type should be correct. Did you find the wrong
return type?

The `RexBuilder.makeLiteral(Object value, RelDataType type, boolean
allowCast)` accepts any values and will cast Integer back to Date
internally.

Regards,
Jark Wu


2017-06-29 12:38 GMT+08:00 郭健 <[hidden email]>:

> Hi all,
>             I am implementing a STR_TO_DATE scalar SQL function to flink,
> and found return type casted from java.sql.Date to Integer in Flink’s
> ExpressionReducer:
> https://github.com/apache/flink/blob/master/flink-
> libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/
> ExpressionReducer.scala#L56
>
> // we need to cast here for RexBuilder.makeLiteral
>
>
>       case (SqlTypeName.DATE, e) =>
>
>
>         Some(
>
>
>           rexBuilder.makeCast(typeFactory.createTypeFromTypeInfo(BasicTypeInfo.INT_TYPE_INFO),
> e)
>
>
>         )
>
>
>
>             so str_to_date('01,5,2013','%d,%m,%Y')" must return an
> Integer, which conflicted with my implementation.
>
>             My question is: why should we do this? I have seen in comments
> the reason to do this here is: “we need to cast here for
> RexBuilder.makeLiteral”, But is it reasonale to change user function’s
> return Type? Should we restore the origin return type after the reduce?
>
>
> Thanks,
> Aegeaner
>
>
>
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Re: [外部邮件] Re: Question about type cast in ExpressionReducer's reduce procedure

郭健
Hi Jark Wu,
        I did see the wrong result type failed the CodeGen compile stage, it throws out exception stack as follow, even before the ExpressionReducer actually restores the origin return
    type:

org.apache.flink.api.common.InvalidProgramException: Table program cannot be compiled. This is a bug. Please file an issue.

        at org.apache.flink.table.codegen.Compiler$class.compile(Compiler.scala:36)
        at org.apache.flink.table.codegen.ExpressionReducer.compile(ExpressionReducer.scala:38)
        at org.apache.flink.table.codegen.ExpressionReducer.reduce(ExpressionReducer.scala:96)
        at org.apache.calcite.rel.rules.ReduceExpressionsRule.reduceExpressionsInternal(ReduceExpressionsRule.java:549)
        at org.apache.calcite.rel.rules.ReduceExpressionsRule.reduceExpressions(ReduceExpressionsRule.java:470)
        at org.apache.calcite.rel.rules.ReduceExpressionsRule.reduceExpressions(ReduceExpressionsRule.java:447)
        at org.apache.calcite.rel.rules.ReduceExpressionsRule$ProjectReduceExpressionsRule.onMatch(ReduceExpressionsRule.java:270)
        at org.apache.calcite.plan.AbstractRelOptPlanner.fireRule(AbstractRelOptPlanner.java:317)
        at org.apache.calcite.plan.hep.HepPlanner.applyRule(HepPlanner.java:506)
        at org.apache.calcite.plan.hep.HepPlanner.applyRules(HepPlanner.java:385)
        at org.apache.calcite.plan.hep.HepPlanner.executeInstruction(HepPlanner.java:251)
        at org.apache.calcite.plan.hep.HepInstruction$RuleInstance.execute(HepInstruction.java:125)
        at org.apache.calcite.plan.hep.HepPlanner.executeProgram(HepPlanner.java:210)
        at org.apache.calcite.plan.hep.HepPlanner.findBestExp(HepPlanner.java:197)
        at org.apache.flink.table.expressions.utils.ExpressionTestBase.addSqlTestExpr(ExpressionTestBase.scala:194)
        at org.apache.flink.table.expressions.utils.ExpressionTestBase.testSqlApi(ExpressionTestBase.scala:277)
        at org.apache.flink.table.expressions.ScalarFunctionsTest.testStrToDate(ScalarFunctionsTest.scala:1516)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
        at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
        at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
        at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
        at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
        at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
        at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
        at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.codehaus.commons.compiler.CompileException: Line 49, Column 23: Assignment conversion not possible from type "java.sql.Date" to type "int"
        at org.codehaus.janino.UnitCompiler.compileError(UnitCompiler.java:11672)
        at org.codehaus.janino.UnitCompiler.assignmentConversion(UnitCompiler.java:10528)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:3452)
        at org.codehaus.janino.UnitCompiler.access$5200(UnitCompiler.java:212)
        at org.codehaus.janino.UnitCompiler$9.visitAssignment(UnitCompiler.java:3416)
        at org.codehaus.janino.UnitCompiler$9.visitAssignment(UnitCompiler.java:3396)
        at org.codehaus.janino.Java$Assignment.accept(Java.java:4300)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:3396)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:2316)
        at org.codehaus.janino.UnitCompiler.access$1700(UnitCompiler.java:212)
        at org.codehaus.janino.UnitCompiler$6.visitExpressionStatement(UnitCompiler.java:1450)
        at org.codehaus.janino.UnitCompiler$6.visitExpressionStatement(UnitCompiler.java:1443)
        at org.codehaus.janino.Java$ExpressionStatement.accept(Java.java:2848)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:1443)
        at org.codehaus.janino.UnitCompiler.compileStatements(UnitCompiler.java:1523)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:1509)
        at org.codehaus.janino.UnitCompiler.access$1600(UnitCompiler.java:212)
        at org.codehaus.janino.UnitCompiler$6.visitBlock(UnitCompiler.java:1449)
        at org.codehaus.janino.UnitCompiler$6.visitBlock(UnitCompiler.java:1443)
        at org.codehaus.janino.Java$Block.accept(Java.java:2753)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:1443)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:2424)
        at org.codehaus.janino.UnitCompiler.access$1800(UnitCompiler.java:212)
        at org.codehaus.janino.UnitCompiler$6.visitIfStatement(UnitCompiler.java:1451)
        at org.codehaus.janino.UnitCompiler$6.visitIfStatement(UnitCompiler.java:1443)
        at org.codehaus.janino.Java$IfStatement.accept(Java.java:2923)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:1443)
        at org.codehaus.janino.UnitCompiler.compileStatements(UnitCompiler.java:1523)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:3052)
        at org.codehaus.janino.UnitCompiler.compileDeclaredMethods(UnitCompiler.java:1313)
        at org.codehaus.janino.UnitCompiler.compileDeclaredMethods(UnitCompiler.java:1286)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:785)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:436)
        at org.codehaus.janino.UnitCompiler.access$400(UnitCompiler.java:212)
        at org.codehaus.janino.UnitCompiler$2.visitPackageMemberClassDeclaration(UnitCompiler.java:390)
        at org.codehaus.janino.UnitCompiler$2.visitPackageMemberClassDeclaration(UnitCompiler.java:385)
        at org.codehaus.janino.Java$PackageMemberClassDeclaration.accept(Java.java:1405)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:385)
        at org.codehaus.janino.UnitCompiler.compileUnit(UnitCompiler.java:357)
        at org.codehaus.janino.SimpleCompiler.cook(SimpleCompiler.java:234)
        at org.codehaus.janino.SimpleCompiler.compileToClassLoader(SimpleCompiler.java:446)
        at org.codehaus.janino.SimpleCompiler.cook(SimpleCompiler.java:213)
        at org.codehaus.janino.SimpleCompiler.cook(SimpleCompiler.java:204)
        at org.codehaus.commons.compiler.Cookable.cook(Cookable.java:80)
        at org.codehaus.commons.compiler.Cookable.cook(Cookable.java:75)
        at org.apache.flink.table.codegen.Compiler$class.compile(Compiler.scala:33)
        ... 40 more





On 6/29/17, 14:37, "Jark Wu" <[hidden email]> wrote:

    Hi Aegeaner,
   
    First of all, the ExpressionReducer actually restores the origin return
    type after reducing, see
    https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/ExpressionReducer.scala#L122
   
    So the reduced result and type should be correct. Did you find the wrong
    return type?
   
    The `RexBuilder.makeLiteral(Object value, RelDataType type, boolean
    allowCast)` accepts any values and will cast Integer back to Date
    internally.
   
    Regards,
    Jark Wu
   
   
    2017-06-29 12:38 GMT+08:00 郭健 <[hidden email]>:
   
    > Hi all,
    >             I am implementing a STR_TO_DATE scalar SQL function to flink,
    > and found return type casted from java.sql.Date to Integer in Flink’s
    > ExpressionReducer:
    > https://github.com/apache/flink/blob/master/flink-
    > libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/
    > ExpressionReducer.scala#L56
    >
    > // we need to cast here for RexBuilder.makeLiteral
    >
    >
    >       case (SqlTypeName.DATE, e) =>
    >
    >
    >         Some(
    >
    >
    >           rexBuilder.makeCast(typeFactory.createTypeFromTypeInfo(BasicTypeInfo.INT_TYPE_INFO),
    > e)
    >
    >
    >         )
    >
    >
    >
    >             so str_to_date('01,5,2013','%d,%m,%Y')" must return an
    > Integer, which conflicted with my implementation.
    >
    >             My question is: why should we do this? I have seen in comments
    > the reason to do this here is: “we need to cast here for
    > RexBuilder.makeLiteral”, But is it reasonale to change user function’s
    > return Type? Should we restore the origin return type after the reduce?
    >
    >
    > Thanks,
    > Aegeaner
    >
    >
    >
   

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Re: [外部邮件] Re: Question about type cast in ExpressionReducer's reduce procedure

Jark Wu
That's wired. Can you print the generated code ?

Add this line before
https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/ExpressionReducer.scala#L96

println(generatedFunction.code)

2017-06-29 14:50 GMT+08:00 郭健 <[hidden email]>:

> Hi Jark Wu,
>         I did see the wrong result type failed the CodeGen compile stage,
> it throws out exception stack as follow, even before the ExpressionReducer
> actually restores the origin return
>     type:
>
> org.apache.flink.api.common.InvalidProgramException: Table program cannot
> be compiled. This is a bug. Please file an issue.
>
>         at org.apache.flink.table.codegen.Compiler$class.
> compile(Compiler.scala:36)
>         at org.apache.flink.table.codegen.ExpressionReducer.
> compile(ExpressionReducer.scala:38)
>         at org.apache.flink.table.codegen.ExpressionReducer.
> reduce(ExpressionReducer.scala:96)
>         at org.apache.calcite.rel.rules.ReduceExpressionsRule.
> reduceExpressionsInternal(ReduceExpressionsRule.java:549)
>         at org.apache.calcite.rel.rules.ReduceExpressionsRule.
> reduceExpressions(ReduceExpressionsRule.java:470)
>         at org.apache.calcite.rel.rules.ReduceExpressionsRule.
> reduceExpressions(ReduceExpressionsRule.java:447)
>         at org.apache.calcite.rel.rules.ReduceExpressionsRule$
> ProjectReduceExpressionsRule.onMatch(ReduceExpressionsRule.java:270)
>         at org.apache.calcite.plan.AbstractRelOptPlanner.fireRule(
> AbstractRelOptPlanner.java:317)
>         at org.apache.calcite.plan.hep.HepPlanner.applyRule(
> HepPlanner.java:506)
>         at org.apache.calcite.plan.hep.HepPlanner.applyRules(
> HepPlanner.java:385)
>         at org.apache.calcite.plan.hep.HepPlanner.executeInstruction(
> HepPlanner.java:251)
>         at org.apache.calcite.plan.hep.HepInstruction$RuleInstance.
> execute(HepInstruction.java:125)
>         at org.apache.calcite.plan.hep.HepPlanner.executeProgram(
> HepPlanner.java:210)
>         at org.apache.calcite.plan.hep.HepPlanner.findBestExp(
> HepPlanner.java:197)
>         at org.apache.flink.table.expressions.utils.ExpressionTestBase.
> addSqlTestExpr(ExpressionTestBase.scala:194)
>         at org.apache.flink.table.expressions.utils.
> ExpressionTestBase.testSqlApi(ExpressionTestBase.scala:277)
>         at org.apache.flink.table.expressions.ScalarFunctionsTest.
> testStrToDate(ScalarFunctionsTest.scala:1516)
>         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>         at sun.reflect.NativeMethodAccessorImpl.invoke(
> NativeMethodAccessorImpl.java:62)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(
> DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:498)
>         at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(
> FrameworkMethod.java:50)
>         at org.junit.internal.runners.model.ReflectiveCallable.run(
> ReflectiveCallable.java:12)
>         at org.junit.runners.model.FrameworkMethod.invokeExplosively(
> FrameworkMethod.java:47)
>         at org.junit.internal.runners.statements.InvokeMethod.
> evaluate(InvokeMethod.java:17)
>         at org.junit.internal.runners.statements.RunBefores.
> evaluate(RunBefores.java:26)
>         at org.junit.internal.runners.statements.RunAfters.evaluate(
> RunAfters.java:27)
>         at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
>         at org.junit.runners.BlockJUnit4ClassRunner.runChild(
> BlockJUnit4ClassRunner.java:78)
>         at org.junit.runners.BlockJUnit4ClassRunner.runChild(
> BlockJUnit4ClassRunner.java:57)
>         at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
>         at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
>         at org.junit.runners.ParentRunner.runChildren(
> ParentRunner.java:288)
>         at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
>         at org.junit.runners.ParentRunner$2.evaluate(
> ParentRunner.java:268)
>         at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
>         at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
>         at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(
> JUnit4IdeaTestRunner.java:68)
>         at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.
> startRunnerWithArgs(IdeaTestRunner.java:51)
>         at com.intellij.rt.execution.junit.JUnitStarter.
> prepareStreamsAndStart(JUnitStarter.java:242)
>         at com.intellij.rt.execution.junit.JUnitStarter.main(
> JUnitStarter.java:70)
> Caused by: org.codehaus.commons.compiler.CompileException: Line 49,
> Column 23: Assignment conversion not possible from type "java.sql.Date" to
> type "int"
>         at org.codehaus.janino.UnitCompiler.compileError(
> UnitCompiler.java:11672)
>         at org.codehaus.janino.UnitCompiler.assignmentConversion(
> UnitCompiler.java:10528)
>         at org.codehaus.janino.UnitCompiler.compile2(
> UnitCompiler.java:3452)
>         at org.codehaus.janino.UnitCompiler.access$5200(
> UnitCompiler.java:212)
>         at org.codehaus.janino.UnitCompiler$9.
> visitAssignment(UnitCompiler.java:3416)
>         at org.codehaus.janino.UnitCompiler$9.
> visitAssignment(UnitCompiler.java:3396)
>         at org.codehaus.janino.Java$Assignment.accept(Java.java:4300)
>         at org.codehaus.janino.UnitCompiler.compile(
> UnitCompiler.java:3396)
>         at org.codehaus.janino.UnitCompiler.compile2(
> UnitCompiler.java:2316)
>         at org.codehaus.janino.UnitCompiler.access$1700(
> UnitCompiler.java:212)
>         at org.codehaus.janino.UnitCompiler$6.visitExpressionStatement(
> UnitCompiler.java:1450)
>         at org.codehaus.janino.UnitCompiler$6.visitExpressionStatement(
> UnitCompiler.java:1443)
>         at org.codehaus.janino.Java$ExpressionStatement.accept(
> Java.java:2848)
>         at org.codehaus.janino.UnitCompiler.compile(
> UnitCompiler.java:1443)
>         at org.codehaus.janino.UnitCompiler.compileStatements(
> UnitCompiler.java:1523)
>         at org.codehaus.janino.UnitCompiler.compile2(
> UnitCompiler.java:1509)
>         at org.codehaus.janino.UnitCompiler.access$1600(
> UnitCompiler.java:212)
>         at org.codehaus.janino.UnitCompiler$6.visitBlock(
> UnitCompiler.java:1449)
>         at org.codehaus.janino.UnitCompiler$6.visitBlock(
> UnitCompiler.java:1443)
>         at org.codehaus.janino.Java$Block.accept(Java.java:2753)
>         at org.codehaus.janino.UnitCompiler.compile(
> UnitCompiler.java:1443)
>         at org.codehaus.janino.UnitCompiler.compile2(
> UnitCompiler.java:2424)
>         at org.codehaus.janino.UnitCompiler.access$1800(
> UnitCompiler.java:212)
>         at org.codehaus.janino.UnitCompiler$6.
> visitIfStatement(UnitCompiler.java:1451)
>         at org.codehaus.janino.UnitCompiler$6.
> visitIfStatement(UnitCompiler.java:1443)
>         at org.codehaus.janino.Java$IfStatement.accept(Java.java:2923)
>         at org.codehaus.janino.UnitCompiler.compile(
> UnitCompiler.java:1443)
>         at org.codehaus.janino.UnitCompiler.compileStatements(
> UnitCompiler.java:1523)
>         at org.codehaus.janino.UnitCompiler.compile(
> UnitCompiler.java:3052)
>         at org.codehaus.janino.UnitCompiler.compileDeclaredMethods(
> UnitCompiler.java:1313)
>         at org.codehaus.janino.UnitCompiler.compileDeclaredMethods(
> UnitCompiler.java:1286)
>         at org.codehaus.janino.UnitCompiler.compile2(
> UnitCompiler.java:785)
>         at org.codehaus.janino.UnitCompiler.compile2(
> UnitCompiler.java:436)
>         at org.codehaus.janino.UnitCompiler.access$400(
> UnitCompiler.java:212)
>         at org.codehaus.janino.UnitCompiler$2.
> visitPackageMemberClassDeclaration(UnitCompiler.java:390)
>         at org.codehaus.janino.UnitCompiler$2.
> visitPackageMemberClassDeclaration(UnitCompiler.java:385)
>         at org.codehaus.janino.Java$PackageMemberClassDeclaration.
> accept(Java.java:1405)
>         at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:385)
>         at org.codehaus.janino.UnitCompiler.compileUnit(
> UnitCompiler.java:357)
>         at org.codehaus.janino.SimpleCompiler.cook(
> SimpleCompiler.java:234)
>         at org.codehaus.janino.SimpleCompiler.compileToClassLoader(
> SimpleCompiler.java:446)
>         at org.codehaus.janino.SimpleCompiler.cook(
> SimpleCompiler.java:213)
>         at org.codehaus.janino.SimpleCompiler.cook(
> SimpleCompiler.java:204)
>         at org.codehaus.commons.compiler.Cookable.cook(Cookable.java:80)
>         at org.codehaus.commons.compiler.Cookable.cook(Cookable.java:75)
>         at org.apache.flink.table.codegen.Compiler$class.
> compile(Compiler.scala:33)
>         ... 40 more
>
>
>
>
>
> On 6/29/17, 14:37, "Jark Wu" <[hidden email]> wrote:
>
>     Hi Aegeaner,
>
>     First of all, the ExpressionReducer actually restores the origin return
>     type after reducing, see
>     https://github.com/apache/flink/blob/master/flink-
> libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/
> ExpressionReducer.scala#L122
>
>     So the reduced result and type should be correct. Did you find the
> wrong
>     return type?
>
>     The `RexBuilder.makeLiteral(Object value, RelDataType type, boolean
>     allowCast)` accepts any values and will cast Integer back to Date
>     internally.
>
>     Regards,
>     Jark Wu
>
>
>     2017-06-29 12:38 GMT+08:00 郭健 <[hidden email]>:
>
>     > Hi all,
>     >             I am implementing a STR_TO_DATE scalar SQL function to
> flink,
>     > and found return type casted from java.sql.Date to Integer in Flink’s
>     > ExpressionReducer:
>     > https://github.com/apache/flink/blob/master/flink-
>     > libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/
>     > ExpressionReducer.scala#L56
>     >
>     > // we need to cast here for RexBuilder.makeLiteral
>     >
>     >
>     >       case (SqlTypeName.DATE, e) =>
>     >
>     >
>     >         Some(
>     >
>     >
>     >           rexBuilder.makeCast(typeFactory.createTypeFromTypeInfo(
> BasicTypeInfo.INT_TYPE_INFO),
>     > e)
>     >
>     >
>     >         )
>     >
>     >
>     >
>     >             so str_to_date('01,5,2013','%d,%m,%Y')" must return an
>     > Integer, which conflicted with my implementation.
>     >
>     >             My question is: why should we do this? I have seen in
> comments
>     > the reason to do this here is: “we need to cast here for
>     > RexBuilder.makeLiteral”, But is it reasonale to change user
> function’s
>     > return Type? Should we restore the origin return type after the
> reduce?
>     >
>     >
>     > Thanks,
>     > Aegeaner
>     >
>     >
>     >
>
>
>