[SPARK-46124] Replace explicit `ArrayOps#toSeq` with `s.c.immutable.ArraySeq.unsafeWrapArray`

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0.0
• Fix Version/s: 4.0.0
• Component/s: DStreams, Kubernetes, ML, MLlib, Spark Core, SQL, Structured Streaming, YARN
• Labels: pull-request-available
• Assignee: Yang Jie
• Reporter: Yang Jie
• Created: 27/Nov/23 14:09
• Updated: 08/Jun/24 03:44
• Resolved: 29/Nov/23 19:10

Description

There is a behavioral difference between Scala 2.13 and 2.12 for explicit `ArrayOps.toSeq` calls, similar to the implicit conversion from `Array` to `Seq`.

In Scala 2.12, it returns a `mutable.WrappedArray`, which does not involve a collection copy.

```scala
Welcome to Scala 2.12.18 (OpenJDK 64-Bit Server VM, Java 17.0.9).
Type in expressions for evaluation. Or try :help.

scala> Array(1,2,3).toSeq
res0: Seq[Int] = WrappedArray(1, 2, 3)
```

However, in Scala 2.13, it returns an `immutable.ArraySeq` that with collection copy.

Since we have always used the non-collection copy behavior for this explicit conversion in the era of Scala 2.12, it is safe to assume that no collection copy is needed for Scala 2.13.

Issue Links

• links to: GitHub Pull Request #44041
• links to: GitHub Pull Request #46886
• links to: GitHub Pull Request #46887