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Posted to dev@flink.apache.org by 郭健 <gu...@immomo.com> on 2017/06/29 04:38:07 UTC
Question about type cast in ExpressionReducer's reduce procedure
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
Re: [外部邮件] Re: Question about type cast in ExpressionReducer's reduce procedure
Posted by Jark Wu <ja...@apache.org>.
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 <gu...@immomo.com>:
> 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" <ja...@apache.org> 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 <gu...@immomo.com>:
>
> > 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
> >
> >
> >
>
>
>
Re: [外部邮件] Re: Question about type cast in ExpressionReducer's reduce procedure
Posted by 郭健 <gu...@immomo.com>.
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" <ja...@apache.org> 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 <gu...@immomo.com>:
> 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
>
>
>
Re: Question about type cast in ExpressionReducer's reduce procedure
Posted by Jark Wu <ja...@apache.org>.
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 <gu...@immomo.com>:
> 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
>
>
>