[GitHub] [spark] viirya opened a new pull request #24576: [SPARK-27671][SQL] Fix error when casting from a nested null in a struct

[GitBox <gi...@apache.org>]

viirya opened a new pull request #24576: [SPARK-27671][SQL] Fix error when casting from a nested null in a struct
URL: https://github.com/apache/spark/pull/24576
 
 
   ## What changes were proposed in this pull request?
   
   When a null in a nested field in struct, casting from the struct throws error, currently.
   
   ```scala
   scala> sql("select cast(struct(1, null) as struct<a:int,b:int>)").show
   scala.MatchError: NullType (of class org.apache.spark.sql.types.NullType$)                                                                             
     at org.apache.spark.sql.catalyst.expressions.Cast.castToInt(Cast.scala:447)                                                                          
     at org.apache.spark.sql.catalyst.expressions.Cast.cast(Cast.scala:635)                                                                               
     at org.apache.spark.sql.catalyst.expressions.Cast.$anonfun$castStruct$1(Cast.scala:603)   
   ```
   
   ```scala
   scala> sql("select * FROM VALUES (('a', (10, null))), (('b', (10, 50))), (('c', null)) AS tab(x, y)").show                                             
   org.apache.spark.sql.AnalysisException: failed to evaluate expression named_struct('col1', 10, 'col2', NULL): NullType (of class org.apache.spark.sql.t
   ypes.NullType$); line 1 pos 14                                                                                                                         
     at org.apache.spark.sql.catalyst.analysis.package$AnalysisErrorAt.failAnalysis(package.scala:47)                                                     
     at org.apache.spark.sql.catalyst.analysis.ResolveInlineTables.$anonfun$convert$6(ResolveInlineTables.scala:106)        
   ```
   
   This fixes the issue.
   
   ## How was this patch tested?
   
   Added tests.

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