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Dongjoon Hyun 78314af580 [SPARK-27123][SQL] Improve CollapseProject to handle projects cross limit/repartition/sample 
## What changes were proposed in this pull request?

`CollapseProject` optimizer rule simplifies some plans by merging the adjacent projects and performing alias substitutions.
```scala
scala> sql("SELECT b c FROM (SELECT a b FROM t)").explain
== Physical Plan ==
*(1) Project [a#5 AS c#1]
+- Scan hive default.t [a#5], HiveTableRelation `default`.`t`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#5]
```

We can do that more complex cases like the following. This PR aims to handle adjacent projects across limit/repartition/sample. Here, repartition means `Repartition`, not `RepartitionByExpression`.

**BEFORE**
```scala
scala> sql("SELECT b c FROM (SELECT /*+ REPARTITION(1) */ a b FROM t)").explain
== Physical Plan ==
*(2) Project [b#0 AS c#1]
+- Exchange RoundRobinPartitioning(1)
   +- *(1) Project [a#5 AS b#0]
      +- Scan hive default.t [a#5], HiveTableRelation `default`.`t`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#5]
```

**AFTER**
```scala
scala> sql("SELECT b c FROM (SELECT /*+ REPARTITION(1) */ a b FROM t)").explain
== Physical Plan ==
Exchange RoundRobinPartitioning(1)
+- *(1) Project [a#11 AS c#7]
   +- Scan hive default.t [a#11], HiveTableRelation `default`.`t`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#11]
```

## How was this patch tested?

Pass the Jenkins with the newly added and updated test cases.

Closes #24049 from dongjoon-hyun/SPARK-27123.

Authored-by: Dongjoon Hyun <dhyun@apple.com>
Signed-off-by: DB Tsai <d_tsai@apple.com>
2019-03-12 21:45:40 +00:00
..
catalyst [SPARK-27123][SQL] Improve CollapseProject to handle projects cross limit/repartition/sample 2019-03-12 21:45:40 +00:00
core [SPARK-27090][CORE] Removing old LEGACY_DRIVER_IDENTIFIER ("<driver>") 2019-03-12 13:29:39 -05:00
hive [SPARK-27118][SQL] Upgrade Hive Metastore Client to the latest versions for Hive 1.0.x/1.1.x 2019-03-09 16:50:10 -08:00
hive-thriftserver [SPARK-27010][SQL] Find out the actual port number when hive.server2.thrift.port=0 2019-03-12 13:38:41 -05:00
create-docs.sh [MINOR][DOCS] Minor doc fixes related with doc build and uses script dir in SQL doc gen script 2017-08-26 13:56:24 +09:00
gen-sql-markdown.py [SPARK-21485][FOLLOWUP][SQL][DOCS] Describes examples and arguments separately, and note/since in SQL built-in function documentation 2017-08-05 10:10:56 -07:00
mkdocs.yml [SPARK-21485][SQL][DOCS] Spark SQL documentation generation for built-in functions 2017-07-26 09:38:51 -07:00
README.md [MINOR][DOC] Fix some typos and grammar issues 2018-04-06 13:37:08 +08:00

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 an extension of SQLContext called HiveContext that allows 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.