[SEDONA-690] Set default metric to use Haversine for KNN join and code refactoring

[zhangfengcdt]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• Yes, and the PR name follows the format [SEDONA-XXX] my subject.

What changes were proposed in this PR?

This PR change the default distance metric to use Haversine distance when use_spheroid = true. It also refactors the join index judgement code to be more readable.

How was this patch tested?

KNNTestSuit

Did this PR include necessary documentation updates?

• No, this PR does not affect any public API so no need to change the documentation.

[Copilot]

Copilot reviewed 3 out of 7 changed files in this pull request and generated no comments.

Files not reviewed (4)

• spark/common/src/main/scala/org/apache/spark/sql/sedona_sql/strategy/join/BroadcastObjectSideKNNJoinExec.scala: Language not supported
• spark/common/src/main/scala/org/apache/spark/sql/sedona_sql/strategy/join/BroadcastQuerySideKNNJoinExec.scala: Language not supported
• spark/common/src/main/scala/org/apache/spark/sql/sedona_sql/strategy/join/KNNJoinExec.scala: Language not supported
• spark/common/src/test/scala/org/apache/sedona/sql/KnnJoinSuite.scala: Language not supported

Comments suppressed due to low confidence (3)

spark/common/src/main/java/org/apache/sedona/core/spatialOperator/JoinQuery.java:830

• Ensure that switching from 'indexedRDD' to 'spatialPartitionedRDD' here is intentional and that it does not adversely impact the join performance or expected partitioning behavior.

queryRDD.spatialPartitionedRDD.zipPartitions(objectRDD.spatialPartitionedRDD, judgement);

spark/common/src/main/java/org/apache/sedona/core/joinJudgement/KnnJoinIndexJudgement.java:48

• The change in generic types alters the method signature; please verify that all downstream usages of KnnJoinIndexJudgement align with this new type ordering to prevent potential type mismatches.

implements FlatMapFunction2<Iterator<T>, Iterator<U>, Pair<T, U>>

spark/common/src/main/java/org/apache/sedona/core/spatialOperator/JoinQuery.java:786

• The updated type for 'broadcastQueryObjects' improves type safety. Please confirm that all its usages are updated accordingly to handle 'UniqueGeometry' objects consistently.

final Broadcast<List<UniqueGeometry<U>>> broadcastQueryObjects;