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### What changes were proposed in this pull request?
Based on a follow up comment in #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 <[email protected]>
Signed-off-by: Takeshi Yamamuro <[email protected]>
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README.md

Apache Spark

Spark is a unified analytics engine for large-scale data processing. It provides high-level APIs in Scala, Java, Python, and R, and an optimized engine that supports general computation graphs for data analysis. It also supports a rich set of higher-level tools including Spark SQL for SQL and DataFrames, MLlib for machine learning, GraphX for graph processing, and Structured Streaming for stream processing.

https://spark.apache.org/

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Online Documentation

You can find the latest Spark documentation, including a programming guide, on the project web page. This README file only contains basic setup instructions.

Building Spark

Spark is built using Apache Maven. To build Spark and its example programs, run:

./build/mvn -DskipTests clean package

(You do not need to do this if you downloaded a pre-built package.)

More detailed documentation is available from the project site, at "Building Spark".

For general development tips, including info on developing Spark using an IDE, see "Useful Developer Tools".

Interactive Scala Shell

The easiest way to start using Spark is through the Scala shell:

./bin/spark-shell

Try the following command, which should return 1,000,000,000:

scala> spark.range(1000 * 1000 * 1000).count()

Interactive Python Shell

Alternatively, if you prefer Python, you can use the Python shell:

./bin/pyspark

And run the following command, which should also return 1,000,000,000:

>>> spark.range(1000 * 1000 * 1000).count()

Example Programs

Spark also comes with several sample programs in the examples directory. To run one of them, use ./bin/run-example <class> [params]. For example:

./bin/run-example SparkPi

will run the Pi example locally.

You can set the MASTER environment variable when running examples to submit examples to a cluster. This can be a mesos:// or spark:// URL, "yarn" to run on YARN, and "local" to run locally with one thread, or "local[N]" to run locally with N threads. You can also use an abbreviated class name if the class is in the examples package. For instance:

MASTER=spark://host:7077 ./bin/run-example SparkPi

Many of the example programs print usage help if no params are given.

Running Tests

Testing first requires building Spark. Once Spark is built, tests can be run using:

./dev/run-tests

Please see the guidance on how to run tests for a module, or individual tests.

There is also a Kubernetes integration test, see resource-managers/kubernetes/integration-tests/README.md

A Note About Hadoop Versions

Spark uses the Hadoop core library to talk to HDFS and other Hadoop-supported storage systems. Because the protocols have changed in different versions of Hadoop, you must build Spark against the same version that your cluster runs.

Please refer to the build documentation at "Specifying the Hadoop Version and Enabling YARN" for detailed guidance on building for a particular distribution of Hadoop, including building for particular Hive and Hive Thriftserver distributions.

Configuration

Please refer to the Configuration Guide in the online documentation for an overview on how to configure Spark.

Contributing

Please review the Contribution to Spark guide for information on how to get started contributing to the project.

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