Github user ueshin commented on a diff in the pull request:
https://github.com/apache/spark/pull/1889#discussion_r16094328
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/dataTypes.scala
---
@@ -372,7 +372,7 @@ object MapType {
* The `valueContainsNull` is true.
*/
def apply(keyType: DataType, valueType: DataType): MapType =
- MapType(keyType: DataType, valueType: DataType, true)
+ MapType(keyType: DataType, valueType: DataType, false)
--- End diff --
Oops, I forgot to change the doc.
I think the default value should be `false` because non nullable by default
is more natural.
For example, when we think `Map[Int, Long]` variable, it can't contain
`null` value.
If we want to add `null` value to the map, we have to declare the variable
as `Map[Int, Any]` or `Map[Int, java.lang.Long]` or something like that.
It is the same way when thinking about the data type.
And this is the same as `ArrayType.containsNull`'s default value.
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