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Yuming Wang 6cd6c438f2 [SPARK-34808][SQL] Removes outer join if it only has DISTINCT on streamed side 
### What changes were proposed in this pull request?

This pr add new rule to removes outer join if it only has distinct on streamed side. For example:
```scala
spark.range(200L).selectExpr("id AS a").createTempView("t1")
spark.range(300L).selectExpr("id AS b").createTempView("t2")
spark.sql("SELECT DISTINCT a FROM t1 LEFT JOIN t2 ON a = b").explain(true)
```

Before this pr:
```
== Optimized Logical Plan ==
Aggregate [a#2L], [a#2L]
+- Project [a#2L]
   +- Join LeftOuter, (a#2L = b#6L)
      :- Project [id#0L AS a#2L]
      :  +- Range (0, 200, step=1, splits=Some(2))
      +- Project [id#4L AS b#6L]
         +- Range (0, 300, step=1, splits=Some(2))
```

After this pr:
```
== Optimized Logical Plan ==
Aggregate [a#2L], [a#2L]
+- Project [id#0L AS a#2L]
   +- Range (0, 200, step=1, splits=Some(2))
```

### Why are the changes needed?

Improve query performance. [DB2](https://www.ibm.com/docs/en/db2-for-zos/11?topic=manipulation-how-db2-simplifies-join-operations) support this feature:
![image](https://user-images.githubusercontent.com/5399861/119594277-0d7c4680-be0e-11eb-8bd4-366d8c4639f0.png)

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Unit test.

Closes #31908 from wangyum/SPARK-34808.

Authored-by: Yuming Wang <yumwang@ebay.com>
Signed-off-by: Yuming Wang <yumwang@ebay.com>
2021-05-31 18:14:15 +08:00
..
catalyst [SPARK-34808][SQL] Removes outer join if it only has DISTINCT on streamed side 2021-05-31 18:14:15 +08:00
core [SPARK-35566][SS] Fix StateStoreRestoreExec output rows 2021-05-31 16:45:56 +09:00
hive [SPARK-35526][CORE][SQL][ML][MLLIB] Re-Cleanup procedure syntax is deprecated compilation warning in Scala 2.13 2021-05-30 16:49:47 -07:00
hive-thriftserver [SPARK-35057][SQL] Group exception messages in hive/thriftserver 2021-05-27 07:31:14 +00:00
create-docs.sh [SPARK-34010][SQL][DODCS] Use python3 instead of python in SQL documentation build 2021-01-05 19:48:10 +09:00
gen-sql-api-docs.py [SPARK-34747][SQL][DOCS] Add virtual operators to the built-in function document 2021-03-19 10:19:26 +09:00
gen-sql-config-docs.py [SPARK-32194][PYTHON] Use proper exception classes instead of plain Exception 2021-05-26 11:54:40 +09:00
gen-sql-functions-docs.py [SPARK-31562][SQL] Update ExpressionDescription for substring, current_date, and current_timestamp 2020-04-26 11:46:52 -07:00
mkdocs.yml [SPARK-30731] Update deprecated Mkdocs option 2020-02-19 17:28:58 +09:00
README.md [SPARK-30510][SQL][DOCS] Publicly document Spark SQL configuration options 2020-02-09 19:20:47 +09:00

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.