Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/17192#discussion_r106797757
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
---
@@ -624,41 +627,58 @@ case class StructToJson(
lazy val writer = new CharArrayWriter()
@transient
- lazy val gen =
- new JacksonGenerator(
- child.dataType.asInstanceOf[StructType],
- writer,
- new JSONOptions(options, timeZoneId.get))
+ lazy val gen = new JacksonGenerator(
+ rowSchema, writer, new JSONOptions(options, timeZoneId.get))
+
+ @transient
+ lazy val rowSchema = child.dataType match {
+ case st: StructType => st
+ case ArrayType(st: StructType, _) => st
+ }
+
+ // This converts rows to the JSON output according to the given schema.
+ @transient
+ lazy val converter: Any => UTF8String = {
+ def getAndReset(): UTF8String = {
+ gen.flush()
+ val json = writer.toString
+ writer.reset()
+ UTF8String.fromString(json)
+ }
+
+ child.dataType match {
+ case _: StructType =>
+ (row: Any) =>
+ gen.write(row.asInstanceOf[InternalRow])
+ getAndReset()
+ case ArrayType(_: StructType, _) =>
+ (arr: Any) =>
+ gen.write(arr.asInstanceOf[ArrayData])
+ getAndReset()
+ }
+ }
override def dataType: DataType = StringType
- override def checkInputDataTypes(): TypeCheckResult = {
- if (StructType.acceptsType(child.dataType)) {
+ override def checkInputDataTypes(): TypeCheckResult = child.dataType
match {
+ case _: StructType | ArrayType(_: StructType, _) =>
--- End diff --
It seems `StructType.acceptsType` and `ArrayType.acceptsType` call
`isInstanceOf[StructType]` and `isInstanceOf[ArrayType]`. `isInstanceOf` and
pattern matching are interchangeable in most cases up to my knowledge.
(I just found a reference
https://www.safaribooksonline.com/library/view/scala-cookbook/9781449340292/ch03s15.html)
Namely, this case below should be fine. (Up to my knowledge, Scala forbids
case-to-case inheritance BTW)
```
scala> case class A()
defined class A
scala> class B extends A
defined class B
scala> new B() match {case _: A => println(1)}
1
```
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