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Wang Gengliang b72b8521d9 [SPARK-21222] Move elimination of Distinct clause from analyzer to optimizer 
## What changes were proposed in this pull request?

Move elimination of Distinct clause from analyzer to optimizer

Distinct clause is useless after MAX/MIN clause. For example,
"Select MAX(distinct a) FROM src from"
is equivalent of
"Select MAX(a) FROM src from"
However, this optimization is implemented in analyzer. It should be in optimizer.

## How was this patch tested?

Unit test

gatorsmile cloud-fan

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Wang Gengliang <ltnwgl@gmail.com>

Closes #18429 from gengliangwang/distinct_opt.
2017-06-29 08:47:31 +08:00
..
catalyst [SPARK-21222] Move elimination of Distinct clause from analyzer to optimizer 2017-06-29 08:47:31 +08:00
core [SPARK-21216][SS] Hive strategies missed in Structured Streaming IncrementalExecution 2017-06-28 10:45:45 -07:00
hive [SPARK-21216][SS] Hive strategies missed in Structured Streaming IncrementalExecution 2017-06-28 10:45:45 -07:00
hive-thriftserver [SPARK-20345][SQL] Fix STS error handling logic on HiveSQLException 2017-06-12 14:05:03 -07:00
README.md [SPARK-16557][SQL] Remove stale doc in sql/README.md 2016-07-14 19:24:42 -07:00

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 allows 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.