Github user NathanHowell commented on a diff in the pull request:
https://github.com/apache/spark/pull/12750#discussion_r61526935
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/InferSchema.scala
---
@@ -246,12 +263,39 @@ private[sql] object InferSchema {
}
case (StructType(fields1), StructType(fields2)) =>
- val newFields = (fields1 ++ fields2).groupBy(field =>
field.name).map {
- case (name, fieldTypes) =>
- val dataType =
fieldTypes.view.map(_.dataType).reduce(compatibleType)
- StructField(name, dataType, nullable = true)
+ // Both fields1 and fields2 should be sorted by name, since
inferField performs sorting.
+ // Therefore, we can take advantage of the fact that we're
merging sorted lists and skip
+ // building a hash map or performing additional sorting.
+ val newFields = new mutable.ArrayBuffer[StructField]()
+
+ var f1Idx = 0
+ var f2Idx = 0
+
+ while (f1Idx < fields1.length && f2Idx < fields2.length) {
+ val f1Name = fields1(f1Idx).name
+ val f2Name = fields2(f2Idx).name
+ if (f1Name == f2Name) {
+ val dataType = compatibleType(fields1(f1Idx).dataType,
fields2(f2Idx).dataType)
+ newFields += StructField(f1Name, dataType, nullable = true)
+ f1Idx += 1
+ f2Idx += 1
+ } else if (f1Name < f2Name) {
+ newFields += fields1(f1Idx)
+ f1Idx += 1
+ } else { // f1Name > f2Name
+ newFields += fields2(f2Idx)
+ f2Idx += 1
+ }
+ }
+ while (f1Idx < fields1.length) {
+ newFields += fields1(f1Idx)
+ f1Idx += 1
+ }
+ while (f2Idx < fields2.length) {
+ newFields += fields2(f2Idx)
+ f2Idx += 1
}
- StructType(newFields.toSeq.sortBy(_.name))
+ StructType(newFields.toSeq)
--- End diff --
`StructType(Seq[StructField])` just calls `toArray` on the fields... so I
would use `toArray` instead of `toSeq` to reduce one allocation.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
