Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/14957#discussion_r84559521
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileSourceStrategy.scala
---
@@ -126,4 +136,52 @@ object FileSourceStrategy extends Strategy with
Logging {
case _ => Nil
}
+
+ private def generateStructFieldsContainsNesting(projects:
Seq[Expression],
+ totalSchema: StructType) :
Seq[StructField] = {
+ def generateStructField(curField: List[String],
+ node: Expression) : Seq[StructField] = {
+ node match {
+ case ai: GetArrayItem =>
+ // Here we drop the previous for simplify array and map support.
+ // Same strategy in GetArrayStructFields and GetMapValue
+ generateStructField(List.empty[String], ai.child)
+ case asf: GetArrayStructFields =>
+ generateStructField(List.empty[String], asf.child)
+ case mv: GetMapValue =>
+ generateStructField(List.empty[String], mv.child)
+ case attr: AttributeReference =>
+ Seq(getFieldRecursively(totalSchema, attr.name :: curField))
+ case sf: GetStructField =>
+ generateStructField(sf.name.get :: curField, sf.child)
+ case _ =>
+ if (node.children.nonEmpty) {
+ node.children.flatMap(child => generateStructField(curField,
child))
+ } else {
+ Seq.empty[StructField]
+ }
+ }
+ }
+
+ def getFieldRecursively(totalSchema: StructType,
+ name: List[String]): StructField = {
+ if (name.length > 1) {
+ val curField = name.head
+ val curFieldType = totalSchema(curField)
+ curFieldType.dataType match {
+ case st: StructType =>
+ val newField = getFieldRecursively(StructType(st.fields),
name.drop(1))
+ StructField(curFieldType.name, StructType(Seq(newField)),
+ curFieldType.nullable, curFieldType.metadata)
+ case _ =>
+ throw new IllegalArgumentException(s"""Field "$curField" is
not struct field.""")
+ }
+ } else {
+ totalSchema(name.head)
+ }
+ }
--- End diff --
This function can be simplified to:
```scala
def getNestedField(schema: StructType, path: Seq[String]): StructField = {
require(path.nonEmpty, "<error message>")
path.tail.foldLeft(schema(path.head)) { (field, name) =>
field.dataType match {
case t: StructType => t(name)
case _ => ??? // Throw exception here
}
}
}
```
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