[SPARK-24027] Support MapType(StringType, DataType) as root type by from_json

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.3.0
• Fix Version/s: 2.4.0
• Component/s: SQL
• Target Version/s: 2.4.0
• Assignee: Max Gekk
• Reporter: Max Gekk
• Created: 19/Apr/18 20:05
• Updated: 14/May/18 21:06
• Resolved: 14/May/18 21:06

Description

Currently, MapType is not supported by the from_json function as the root type. For example, the following code doesn't work on Spark 2.3:

scala> import org.apache.spark.sql.types._
import org.apache.spark.sql.types._

scala> val schema = MapType(StringType, IntegerType)
schema: org.apache.spark.sql.types.MapType = MapType(StringType,IntegerType,true)

scala> val in = Seq("""{"a": 1, "b": 2, "c": 3}""").toDS()
in: org.apache.spark.sql.Dataset[String] = [value: string]

scala> in.select(from_json($"value", schema, Map[String, String]())).collect()
org.apache.spark.sql.AnalysisException: cannot resolve 'jsontostructs(`value`)' due to data type mismatch: Input schema map<string,int> must be a struct or an array of structs.

Purpose of the ticket is to support MapType with StringType as keys type.

Issue Links

• links to: [Github] Pull Request #21108 (MaxGekk)