Minor Description
When casting a struct with a Timestamp field, a MatchError is thrown (pasted below).
the root cause for this is in org.apache.spark.sql.catalyst.expressions.Cast#cast (https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala#L419).
case dt if dt == child.dataType => identity[Any]
should be modified to:
case dt if dt == from => identity[Any]
it seems to explode for timestamp because org.apache.spark.sql.catalyst.expressions.Cast#castToTimestamp does'nt have an identity check or fallback case in its pattern matching.
I'll shortly open a pull request with a failing test case and a fix.
Caused by: scala.MatchError: TimestampType (of class org.apache.spark.sql.types.TimestampType$)
at org.apache.spark.sql.catalyst.expressions.Cast.castToTimestamp(Cast.scala:185)
at org.apache.spark.sql.catalyst.expressions.Cast.org$apache$spark$sql$catalyst$expressions$Cast$$cast(Cast.scala:424)
at org.apache.spark.sql.catalyst.expressions.Cast$$anonfun$1.apply(Cast.scala:403)
at org.apache.spark.sql.catalyst.expressions.Cast$$anonfun$1.apply(Cast.scala:402)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
at scala.collection.mutable.ArrayOps$ofRef.map(ArrayOps.scala:186)
at org.apache.spark.sql.catalyst.expressions.Cast.castStruct(Cast.scala:402)
at org.apache.spark.sql.catalyst.expressions.Cast.org$apache$spark$sql$catalyst$expressions$Cast$$cast(Cast.scala:435)
at org.apache.spark.sql.catalyst.expressions.Cast.cast$lzycompute(Cast.scala:443)
at org.apache.spark.sql.catalyst.expressions.Cast.cast(Cast.scala:443)
at org.apache.spark.sql.catalyst.expressions.Cast.nullSafeEval(Cast.scala:445)
at org.apache.spark.sql.catalyst.expressions.UnaryExpression.eval(Expression.scala:324)
at org.apache.spark.sql.catalyst.expressions.ExpressionEvalHelper$class.evaluate(ExpressionEvalHelper.scala:80)
at org.apache.spark.sql.catalyst.expressions.CastSuite.evaluate(CastSuite.scala:33)
... 58 more
