### What changes were proposed in this pull request?
Based on a follow up comment in https://github.com/apache/spark/pull/28123, where we can coalesce buckets for shuffled hash join as well. The note here is we only coalesce the buckets from shuffled hash join stream side (i.e. the side not building hash map), so we don't need to worry about OOM when coalescing multiple buckets in one task for building hash map.
> If you refactor some codes with changing classes, showing the class hierarchy will help reviewers.
Refactor existing physical plan rule `CoalesceBucketsInSortMergeJoin` to `CoalesceBucketsInJoin`, for covering shuffled hash join as well.
Refactor existing unit test `CoalesceBucketsInSortMergeJoinSuite` to `CoalesceBucketsInJoinSuite`, for covering shuffled hash join as well.
### Why are the changes needed?
Avoid shuffle for joining different bucketed tables, is also useful for shuffled hash join. In production, we are seeing users to use shuffled hash join to join bucketed tables (set `spark.sql.join.preferSortMergeJoin`=false, to avoid sort), and this can help avoid shuffle if number of buckets are not same.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Added unit tests in `CoalesceBucketsInJoinSuite` for verifying shuffled hash join physical plan.
### Performance number per request from maropu
I was looking at TPCDS per suggestion from maropu. But I found most of queries from TPCDS are doing aggregate, and only several ones are doing join. None of input tables are bucketed. So I took the approach to test a modified version of `TPCDS q93` as
```
SELECT ss_ticket_number, sr_ticket_number
FROM store_sales
JOIN store_returns
ON ss_ticket_number = sr_ticket_number
```
And make `store_sales` and `store_returns` to be bucketed tables.
Physical query plan without coalesce:
```
ShuffledHashJoin [ss_ticket_number#109L], [sr_ticket_number#120L], Inner, BuildLeft
:- Exchange hashpartitioning(ss_ticket_number#109L, 4), true, [id=#67]
: +- *(1) Project [ss_ticket_number#109L]
: +- *(1) Filter isnotnull(ss_ticket_number#109L)
: +- *(1) ColumnarToRow
: +- FileScan parquet default.store_sales[ss_ticket_number#109L] Batched: true, DataFilters: [isnotnull(ss_ticket_number#109L)], Format: Parquet, Location: InMemoryFileIndex[file:/Users/chengsu/spark/spark-warehouse/store_sales], PartitionFilters: [], PushedFilters: [IsNotNull(ss_ticket_number)], ReadSchema: struct<ss_ticket_number:bigint>, SelectedBucketsCount: 2 out of 2
+- *(2) Project [sr_returned_date_sk#111L, sr_return_time_sk#112L, sr_item_sk#113L, sr_customer_sk#114L, sr_cdemo_sk#115L, sr_hdemo_sk#116L, sr_addr_sk#117L, sr_store_sk#118L, sr_reason_sk#119L, sr_ticket_number#120L, sr_return_quantity#121L, sr_return_amt#122, sr_return_tax#123, sr_return_amt_inc_tax#124, sr_fee#125, sr_return_ship_cost#126, sr_refunded_cash#127, sr_reversed_charge#128, sr_store_credit#129, sr_net_loss#130]
+- *(2) Filter isnotnull(sr_ticket_number#120L)
+- *(2) ColumnarToRow
+- FileScan parquet default.store_returns[sr_returned_date_sk#111L,sr_return_time_sk#112L,sr_item_sk#113L,sr_customer_sk#114L,sr_cdemo_sk#115L,sr_hdemo_sk#116L,sr_addr_sk#117L,sr_store_sk#118L,sr_reason_sk#119L,sr_ticket_number#120L,sr_return_quantity#121L,sr_return_amt#122,sr_return_tax#123,sr_return_amt_inc_tax#124,sr_fee#125,sr_return_ship_cost#126,sr_refunded_cash#127,sr_reversed_charge#128,sr_store_credit#129,sr_net_loss#130] Batched: true, DataFilters: [isnotnull(sr_ticket_number#120L)], Format: Parquet, Location: InMemoryFileIndex[file:/Users/chengsu/spark/spark-warehouse/store_returns], PartitionFilters: [], PushedFilters: [IsNotNull(sr_ticket_number)], ReadSchema: struct<sr_returned_date_sk:bigint,sr_return_time_sk:bigint,sr_item_sk:bigint,sr_customer_sk:bigin..., SelectedBucketsCount: 4 out of 4
```
Physical query plan with coalesce:
```
ShuffledHashJoin [ss_ticket_number#109L], [sr_ticket_number#120L], Inner, BuildLeft
:- *(1) Project [ss_ticket_number#109L]
: +- *(1) Filter isnotnull(ss_ticket_number#109L)
: +- *(1) ColumnarToRow
: +- FileScan parquet default.store_sales[ss_ticket_number#109L] Batched: true, DataFilters: [isnotnull(ss_ticket_number#109L)], Format: Parquet, Location: InMemoryFileIndex[file:/Users/chengsu/spark/spark-warehouse/store_sales], PartitionFilters: [], PushedFilters: [IsNotNull(ss_ticket_number)], ReadSchema: struct<ss_ticket_number:bigint>, SelectedBucketsCount: 2 out of 2
+- *(2) Project [sr_returned_date_sk#111L, sr_return_time_sk#112L, sr_item_sk#113L, sr_customer_sk#114L, sr_cdemo_sk#115L, sr_hdemo_sk#116L, sr_addr_sk#117L, sr_store_sk#118L, sr_reason_sk#119L, sr_ticket_number#120L, sr_return_quantity#121L, sr_return_amt#122, sr_return_tax#123, sr_return_amt_inc_tax#124, sr_fee#125, sr_return_ship_cost#126, sr_refunded_cash#127, sr_reversed_charge#128, sr_store_credit#129, sr_net_loss#130]
+- *(2) Filter isnotnull(sr_ticket_number#120L)
+- *(2) ColumnarToRow
+- FileScan parquet default.store_returns[sr_returned_date_sk#111L,sr_return_time_sk#112L,sr_item_sk#113L,sr_customer_sk#114L,sr_cdemo_sk#115L,sr_hdemo_sk#116L,sr_addr_sk#117L,sr_store_sk#118L,sr_reason_sk#119L,sr_ticket_number#120L,sr_return_quantity#121L,sr_return_amt#122,sr_return_tax#123,sr_return_amt_inc_tax#124,sr_fee#125,sr_return_ship_cost#126,sr_refunded_cash#127,sr_reversed_charge#128,sr_store_credit#129,sr_net_loss#130] Batched: true, DataFilters: [isnotnull(sr_ticket_number#120L)], Format: Parquet, Location: InMemoryFileIndex[file:/Users/chengsu/spark/spark-warehouse/store_returns], PartitionFilters: [], PushedFilters: [IsNotNull(sr_ticket_number)], ReadSchema: struct<sr_returned_date_sk:bigint,sr_return_time_sk:bigint,sr_item_sk:bigint,sr_customer_sk:bigin..., SelectedBucketsCount: 4 out of 4 (Coalesced to 2)
```
Run time improvement as 50% of wall clock time:
```
Java HotSpot(TM) 64-Bit Server VM 1.8.0_181-b13 on Mac OS X 10.15.4
Intel(R) Core(TM) i9-9980HK CPU 2.40GHz
shuffle hash join: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
------------------------------------------------------------------------------------------------------------------------
shuffle hash join coalesce bucket off 1541 1664 106 1.9 535.1 1.0X
shuffle hash join coalesce bucket on 1060 1169 81 2.7 368.1 1.5X
```
Closes#29079 from c21/split-bucket.
Authored-by: Cheng Su <chengsu@fb.com>
Signed-off-by: Takeshi Yamamuro <yamamuro@apache.org>
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