viirya commented on a change in pull request #29942:
URL: https://github.com/apache/spark/pull/29942#discussion_r499355958
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/OptimizeJsonExprs.scala
##########
@@ -28,10 +28,36 @@ import org.apache.spark.sql.types.{ArrayType, StructType}
* The optimization includes:
* 1. JsonToStructs(StructsToJson(child)) => child.
* 2. Prune unnecessary columns from GetStructField/GetArrayStructFields +
JsonToStructs.
+ * 3 struct(from_json.col1, from_json.col2, from_json.col3...) =>
struct(from_json)
*/
object OptimizeJsonExprs extends Rule[LogicalPlan] {
override def apply(plan: LogicalPlan): LogicalPlan = plan transform {
case p => p.transformExpressions {
+
+ case c: CreateNamedStruct
+ if c.valExprs.forall(v => v.isInstanceOf[GetStructField] &&
+ v.asInstanceOf[GetStructField].child.isInstanceOf[JsonToStructs]) =>
+ val jsonToStructs = c.valExprs.map(_.children(0))
+ val semanticEqual =
jsonToStructs.tail.forall(jsonToStructs.head.semanticEquals(_))
+ val sameFieldName = c.names.zip(c.valExprs).forall {
+ case (name, valExpr: GetStructField) =>
+ name.toString == valExpr.childSchema(valExpr.ordinal).name
+ case (_, _) => false
+ }
+
+ // If we create struct from various fields of the same `JsonToStructs`
and we don't
+ // alias field names.
+ if (semanticEqual && sameFieldName) {
+ val fromJson =
jsonToStructs.head.asInstanceOf[JsonToStructs].copy(schema = c.dataType)
+ val nullFields = c.children.grouped(2).map {
+ case Seq(name, value) => Seq(name, Literal(null, value.dataType))
+ }.flatten.toSeq
+
+ If(IsNull(fromJson.child), c.copy(children = nullFields),
KnownNotNull(fromJson))
Review comment:
`JsonToStructs`'s `nullable` is true. If the input json to
`JsonToStructs` is null, we will get a null output. But `CreateNamedStruct`'s
`nullable` is false, so here we need to keep nullability unchanged by wrapping
them with a `If(IsNull...)`.
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