Github user goldmedal commented on a diff in the pull request:
https://github.com/apache/spark/pull/18875#discussion_r131946027
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
---
@@ -659,13 +660,19 @@ case class StructsToJson(
(arr: Any) =>
gen.write(arr.asInstanceOf[ArrayData])
getAndReset()
+ case MapType(_: DataType, _: StructType, _: Boolean) =>
+ (map: Any) =>
+ val mapType = child.dataType.asInstanceOf[MapType]
+ gen.write(map.asInstanceOf[MapData], mapType)
+ getAndReset()
}
}
override def dataType: DataType = StringType
override def checkInputDataTypes(): TypeCheckResult = child.dataType
match {
- case _: StructType | ArrayType(_: StructType, _) =>
+ case _: StructType | ArrayType(_: StructType, _) |
+ MapType(_: DataType, _: StructType, _: Boolean) =>
--- End diff --
yeah, just like @viirya said. This expression is named `StructsToJson`.
Another reason is that it use `JacksonGenerator` which will need a
`rowSchema` when initializing to generate JSON string. Therefore, it must be
restricted to `StructType` here.
or can we create another expression to support arbitrary map type?
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