[SPARK-32767][SQL] Bucket join should work if spark.sql.shuffle.partitions larger than bucket number

[wangyum]

What changes were proposed in this pull request?

Bucket join should work if spark.sql.shuffle.partitions larger than bucket number, such as:

spark.range(1000).write.bucketBy(432, "id").saveAsTable("t1")
spark.range(1000).write.bucketBy(34, "id").saveAsTable("t2")
sql("set spark.sql.shuffle.partitions=600")
sql("set spark.sql.autoBroadcastJoinThreshold=-1")
sql("select * from t1 join t2 on t1.id = t2.id").explain()

Before this pr:

== Physical Plan ==
*(5) SortMergeJoin [id#26L], [id#27L], Inner
:- *(2) Sort [id#26L ASC NULLS FIRST], false, 0
:  +- Exchange hashpartitioning(id#26L, 600), true
:     +- *(1) Filter isnotnull(id#26L)
:        +- *(1) ColumnarToRow
:           +- FileScan parquet default.t1[id#26L] Batched: true, DataFilters: [isnotnull(id#26L)], Format: Parquet, PartitionFilters: [], PushedFilters: [IsNotNull(id)], ReadSchema: struct<id:bigint>, SelectedBucketsCount: 432 out of 432
+- *(4) Sort [id#27L ASC NULLS FIRST], false, 0
   +- Exchange hashpartitioning(id#27L, 600), true
      +- *(3) Filter isnotnull(id#27L)
         +- *(3) ColumnarToRow
            +- FileScan parquet default.t2[id#27L] Batched: true, DataFilters: [isnotnull(id#27L)], Format: Parquet, PartitionFilters: [], PushedFilters: [IsNotNull(id)], ReadSchema: struct<id:bigint>, SelectedBucketsCount: 34 out of 34

After this pr:

== Physical Plan ==
*(4) SortMergeJoin [id#26L], [id#27L], Inner
:- *(1) Sort [id#26L ASC NULLS FIRST], false, 0
:  +- *(1) Filter isnotnull(id#26L)
:     +- *(1) ColumnarToRow
:        +- FileScan parquet default.t1[id#26L] Batched: true, DataFilters: [isnotnull(id#26L)], Format: Parquet, PartitionFilters: [], PushedFilters: [IsNotNull(id)], ReadSchema: struct<id:bigint>, SelectedBucketsCount: 432 out of 432
+- *(3) Sort [id#27L ASC NULLS FIRST], false, 0
   +- Exchange hashpartitioning(id#27L, 432), true
      +- *(2) Filter isnotnull(id#27L)
         +- *(2) ColumnarToRow
            +- FileScan parquet default.t2[id#27L] Batched: true, DataFilters: [isnotnull(id#27L)], Format: Parquet, PartitionFilters: [], PushedFilters: [IsNotNull(id)], ReadSchema: struct<id:bigint>, SelectedBucketsCount: 34 out of 34

Why are the changes needed?

Spark 2.4 support this.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Unit test.

[SparkQA]

Test build #128155 has finished for PR 29612 at commit e59df34.

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

[cloud-fan]

thanks, merging to master!