maropu commented on a change in pull request #24179: [SPARK-27241][SQL] Support
map_keys in SelectedField
URL: https://github.com/apache/spark/pull/24179#discussion_r268137902
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SelectedField.scala
##########
@@ -97,6 +97,19 @@ object SelectedField {
val MapType(keyType, _, valueContainsNull) = child.dataType
val opt = dataTypeOpt.map(dt => MapType(keyType, dt,
valueContainsNull))
selectField(child, opt)
+ case MapKeys(child) =>
+ val MapType(_, valueType, valueContainsNull) = child.dataType
+ // MapKeys does not select a field from a struct (i.e. prune the
struct) so it can't be
+ // the top-level extractor. However it can be part of an extractor
chain.
+ val newKeyType = dataTypeOpt match {
+ case None => None
+ case Some(ArrayType(dataType, _)) => Some(dataType)
+ case Some(x) =>
+ // This should not happen.
+ throw new AnalysisException(s"DataType '$x' is not supported by
MapKeys.")
+ }
+ val opt = dataTypeOpt.map(dt => MapType(newKeyType.get, valueType,
valueContainsNull))
Review comment:
nit: like this?
```
case MapKeys(child) =>
val MapType(_, valueType, valueContainsNull) = child.dataType
// MapKeys does not select a field from a struct (i.e. prune the
struct) so it can't be
// the top-level extractor. However it can be part of an extractor
chain.
val opt = dataTypeOpt.map {
case ArrayType(dataType, _) => MapType(dataType, valueType,
valueContainsNull)
case x =>
// This should not happen.
throw new AnalysisException(s"DataType '$x' is not supported by
MapKeys.")
}
selectField(child, opt)
```
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