fe07521c9e
### What changes were proposed in this pull request?
Currently `ShuffledHashJoin.outputPartitioning` inherits from `HashJoin.outputPartitioning`, which only preserves stream side partitioning (`HashJoin.scala`):
```
override def outputPartitioning: Partitioning = streamedPlan.outputPartitioning
```
This loses build side partitioning information, and causes extra shuffle if there's another join / group-by after this join.
Example:
```
withSQLConf(
SQLConf.AUTO_BROADCASTJOIN_THRESHOLD.key -> "50",
SQLConf.SHUFFLE_PARTITIONS.key -> "2",
SQLConf.PREFER_SORTMERGEJOIN.key -> "false") {
val df1 = spark.range(10).select($"id".as("k1"))
val df2 = spark.range(30).select($"id".as("k2"))
Seq("inner", "cross").foreach(joinType => {
val plan = df1.join(df2, $"k1" === $"k2", joinType).groupBy($"k1").count()
.queryExecution.executedPlan
assert(plan.collect { case _: ShuffledHashJoinExec => true }.size === 1)
// No extra shuffle before aggregate
assert(plan.collect { case _: ShuffleExchangeExec => true }.size === 2)
})
}
```
Current physical plan (having an extra shuffle on `k1` before aggregate)
```
*(4) HashAggregate(keys=[k1#220L], functions=[count(1)], output=[k1#220L, count#235L])
+- Exchange hashpartitioning(k1#220L, 2), true, [id=#117]
+- *(3) HashAggregate(keys=[k1#220L], functions=[partial_count(1)], output=[k1#220L, count#239L])
+- *(3) Project [k1#220L]
+- ShuffledHashJoin [k1#220L], [k2#224L], Inner, BuildLeft
:- Exchange hashpartitioning(k1#220L, 2), true, [id=#109]
: +- *(1) Project [id#218L AS k1#220L]
: +- *(1) Range (0, 10, step=1, splits=2)
+- Exchange hashpartitioning(k2#224L, 2), true, [id=#111]
+- *(2) Project [id#222L AS k2#224L]
+- *(2) Range (0, 30, step=1, splits=2)
```
Ideal physical plan (no shuffle on `k1` before aggregate)
```
*(3) HashAggregate(keys=[k1#220L], functions=[count(1)], output=[k1#220L, count#235L])
+- *(3) HashAggregate(keys=[k1#220L], functions=[partial_count(1)], output=[k1#220L, count#239L])
+- *(3) Project [k1#220L]
+- ShuffledHashJoin [k1#220L], [k2#224L], Inner, BuildLeft
:- Exchange hashpartitioning(k1#220L, 2), true, [id=#107]
: +- *(1) Project [id#218L AS k1#220L]
: +- *(1) Range (0, 10, step=1, splits=2)
+- Exchange hashpartitioning(k2#224L, 2), true, [id=#109]
+- *(2) Project [id#222L AS k2#224L]
+- *(2) Range (0, 30, step=1, splits=2)
```
This can be fixed by overriding `outputPartitioning` method in `ShuffledHashJoinExec`, similar to `SortMergeJoinExec`.
In addition, also fix one typo in `HashJoin`, as that code path is shared between broadcast hash join and shuffled hash join.
### Why are the changes needed?
To avoid shuffle (for queries having multiple joins or group-by), for saving CPU and IO.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Added unit test in `JoinSuite`.
Closes #29130 from c21/shj.
Authored-by: Cheng Su <chengsu@fb.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
|
||
|---|---|---|
| .. | ||
| catalyst | ||
| core | ||
| hive | ||
| hive-thriftserver | ||
| create-docs.sh | ||
| gen-sql-api-docs.py | ||
| gen-sql-config-docs.py | ||
| gen-sql-functions-docs.py | ||
| mkdocs.yml | ||
| README.md | ||
Spark SQL
This module provides support for executing relational queries expressed in either SQL or the DataFrame/Dataset API.
Spark SQL is broken up into four subprojects:
- Catalyst (sql/catalyst) - An implementation-agnostic framework for manipulating trees of relational operators and expressions.
- Execution (sql/core) - A query planner / execution engine for translating Catalyst's logical query plans into Spark RDDs. This component also includes a new public interface, SQLContext, that allows users to execute SQL or LINQ statements against existing RDDs and Parquet files.
- Hive Support (sql/hive) - Includes extensions that allow users to write queries using a subset of HiveQL and access data from a Hive Metastore using Hive SerDes. There are also wrappers that allow users to run queries that include Hive UDFs, UDAFs, and UDTFs.
- HiveServer and CLI support (sql/hive-thriftserver) - Includes support for the SQL CLI (bin/spark-sql) and a HiveServer2 (for JDBC/ODBC) compatible server.
Running ./sql/create-docs.sh generates SQL documentation for built-in functions under sql/site, and SQL configuration documentation that gets included as part of configuration.md in the main docs directory.