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Yuming Wang 4a17e7a5ae [SPARK-35906][SQL] Remove order by if the maximum number of rows less than or equal to 1 
### What changes were proposed in this pull request?

This PR removes order by if the maximum number of rows less than or equal to 1. For example:
```scala
spark.sql("select count(*) from range(1, 10, 2, 2) order by 1 limit 10").explain("cost")
```
Before this pr:
```
== Optimized Logical Plan ==
Sort [count(1)#2L ASC NULLS FIRST], true, Statistics(sizeInBytes=16.0 B)
+- Aggregate [count(1) AS count(1)#2L], Statistics(sizeInBytes=16.0 B, rowCount=1)
   +- Project, Statistics(sizeInBytes=20.0 B)
      +- Range (1, 10, step=2, splits=Some(2)), Statistics(sizeInBytes=40.0 B, rowCount=5)
```

After this pr:
```
== Optimized Logical Plan ==
Aggregate [count(1) AS count(1)#2L], Statistics(sizeInBytes=16.0 B, rowCount=1)
+- Project, Statistics(sizeInBytes=20.0 B)
   +- Range (1, 10, step=2, splits=Some(2)), Statistics(sizeInBytes=40.0 B, rowCount=5)
```

### Why are the changes needed?

Improve query performance.

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

No.

### How was this patch tested?

Unit test.

Closes #33100 from wangyum/SPARK-35906.

Authored-by: Yuming Wang <yumwang@ebay.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
2021-06-29 11:04:54 -07:00
..
catalyst [SPARK-35906][SQL] Remove order by if the maximum number of rows less than or equal to 1 2021-06-29 11:04:54 -07:00
core [SPARK-35906][SQL] Remove order by if the maximum number of rows less than or equal to 1 2021-06-29 11:04:54 -07:00
hive [SPARK-35747][CORE] Avoid printing full Exception stack trace, if Hbase/Kafka/Hive services are not running in a secure cluster 2021-06-23 23:12:02 -07:00
hive-thriftserver [SPARK-35838][BUILD][TESTS] Ensure all modules can be maven test independently in Scala 2.13 2021-06-22 06:31:24 -07:00
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.