[SPARK-14317] [SQL] Cleanup hash join

[davies]

What changes were proposed in this pull request?

This PR did a few cleanup on HashedRelation and HashJoin:

1. Merge HashedRelation and UniqueHashedRelation together
2. Return an iterator from HashedRelation, so we donot need a create many UnsafeRow objects.
3. Return a copy of HashedRelation for thread-safety in BroadcastJoin, so we can re-use the UnafeRow objects.
4. Cleanup HashJoin, share most of the code between BroadcastHashJoin and ShuffleHashJoin
5. Removed UniqueLongHashedRelation, which will be replaced by LongUnsafeMap (another PR).
6. Update benchmark, before this patch, the selectivity of joins are too high.

How was this patch tested?

Existing tests.

[davies]

cc @rxin @nongli @JoshRosen @sameeragarwal

[SparkQA]

Test build #54674 has finished for PR 12102 at commit 52ed299.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #54683 has finished for PR 12102 at commit 37724be.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

what does long duplicated mean? do you mean non-unique key?

[davies]

Yes

[SparkQA]

Test build #54795 has finished for PR 12102 at commit 0771d8b.

• This patch fails Scala style tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #54796 has finished for PR 12102 at commit e519a41.

• This patch passes all tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[rxin]

LGTM

[davies]

Merging this into master, thanks!

[SparkQA]

Test build #54863 has finished for PR 12102 at commit 0bd71c4.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #54864 has finished for PR 12102 at commit 9690304.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.