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Reynold Xin b78e3849b2 [SPARK-21042][SQL] Document Dataset.union is resolution by position 
## What changes were proposed in this pull request?
Document Dataset.union is resolution by position, not by name, since this has been a confusing point for a lot of users.

## How was this patch tested?
N/A - doc only change.

Author: Reynold Xin <rxin@databricks.com>

Closes #18256 from rxin/SPARK-21042.
2017-06-09 18:29:33 -07:00
..
catalyst [SPARK-20918][SQL] Use FunctionIdentifier as function identifiers in FunctionRegistry 2017-06-09 10:16:30 -07:00
core [SPARK-21042][SQL] Document Dataset.union is resolution by position 2017-06-09 18:29:33 -07:00
hive [SPARK-20918][SQL] Use FunctionIdentifier as function identifiers in FunctionRegistry 2017-06-09 10:16:30 -07:00
hive-thriftserver [SPARK-20966][WEB-UI][SQL] Table data is not sorted by startTime time desc, time is not formatted and redundant code in JDBC/ODBC Server page. 2017-06-07 10:18:40 +01:00
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.