Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/16881#discussion_r100477537
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
---
@@ -496,7 +496,7 @@ case class JsonToStruct(schema: StructType, options:
Map[String, String], child:
override def dataType: DataType = schema
override def nullSafeEval(json: Any): Any = {
- try parser.parse(json.toString).head catch {
+ try parser.parse(json.toString).headOption.orNull catch {
--- End diff --
(Not for this PR but maybe loosely related I guess) I was thinking it is a
bit odd that we support to only read the single row when it is a json array. It
seems, for example,
```scala
import org.apache.spark.sql.functions._
import org.apache.spark.sql.types._
val schema = StructType(StructField("a", IntegerType) :: Nil)
Seq(("""[{"a": 1}, {"a":
2}]""")).toDF("struct").select(from_json(col("struct"), schema)).show()
+--------------------+
|jsontostruct(struct)|
+--------------------+
| [1]|
+--------------------+
```
I think maybe we should not support this in that function or it should work
like a generator expression.
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