[jira] [Commented] (CALCITE-4498) Cannot deduce type of CASE expression which returns a struct that contains a NULL type

["Limian Zhang (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17284307#comment-17284307 ] 

Limian Zhang commented on CALCITE-4498:
---------------------------------------

Yeah, that makes sense, it's my bad, I just changed accordingly.

> Cannot deduce type of CASE expression which returns a struct that contains a NULL type
> --------------------------------------------------------------------------------------
>
>                 Key: CALCITE-4498
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4498
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>         Environment: jvm 1.8.0_121
>            Reporter: Limian Zhang
>            Priority: Major
>
> in [code1|https://github.com/apache/calcite/blob/404f968f6079360621896e6ee20ec12488a40bc2/core/src/main/java/org/apache/calcite/sql/type/SqlTypeFactoryImpl.java#L291] and [code2|https://github.com/apache/calcite/blob/f1da65504e598928cf77aa6a7244552692ae2529/core/src/main/java/org/apache/calcite/rel/type/RelDataTypeFactoryImpl.java#L224] the {{types}} could well be a List of [NULL (not java null point but SqlTypeName.NULL), Row], thus when this {{types}} gets passed down at code1 to code2, and in code 2 line 225, if you try to call `type0.getFieldCount();` You will hit a NullPointerException since the NULL SQL type has NULL as fieldList, thus calling `getFieldCount` will throw NPE.
> stack trace:
> {code:java}
> Exception in thread "main" java.lang.NullPointerException
> at org.apache.calcite.rel.type.RelDataTypeImpl.getFieldCount(RelDataTypeImpl.java:156)
> at org.apache.calcite.rel.type.RelDataTypeFactoryImpl.leastRestrictiveStructuredType(RelDataTypeFactoryImpl.java:223)
> at org.apache.calcite.sql.type.SqlTypeFactoryImpl.leastRestrictiveSqlType(SqlTypeFactoryImpl.java:285)
> at org.apache.calcite.sql.type.SqlTypeFactoryImpl.leastRestrictive(SqlTypeFactoryImpl.java:156)
> {code}
> The above scenario could happen when we try to derive the type of a SqlCaseCall ([e.g.|https://github.com/apache/calcite/blob/f1da65504e598928cf77aa6a7244552692ae2529/core/src/main/java/org/apache/calcite/sql/fun/SqlCaseOperator.java#L172]) where it's like this and we will call the above code path.
> CASE
>      WHEN _condition1_ THEN _NULL_
>      ELSE Some_StructType
>  END;
>  
> basically i think the fix should be in code2, ignore the NULL type in the {{types}}, and only go through the non-null types to get the least restrictive.
>  
>  
>   
>   
>  



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