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wangguangxin.cn 73183b3c8c [SPARK-11412][SQL] Support merge schema for ORC 
## What changes were proposed in this pull request?

Currently, ORC's `inferSchema` is implemented as randomly choosing one ORC file and reading its schema.

This PR follows the behavior of Parquet, it implements merge schemas logic by reading all ORC files in parallel through a spark job.

Users can enable merge schema by `spark.read.orc("xxx").option("mergeSchema", "true")` or by setting `spark.sql.orc.mergeSchema` to `true`, the prior one has higher priority.

## How was this patch tested?
tested by UT OrcUtilsSuite.scala

Closes #24043 from WangGuangxin/SPARK-11412.

Lead-authored-by: wangguangxin.cn <wangguangxin.cn@gmail.com>
Co-authored-by: wangguangxin.cn <wangguangxin.cn@bytedance.com>
Signed-off-by: gatorsmile <gatorsmile@gmail.com>
2019-06-29 17:08:31 -07:00
..
catalyst [SPARK-11412][SQL] Support merge schema for ORC 2019-06-29 17:08:31 -07:00
core [SPARK-11412][SQL] Support merge schema for ORC 2019-06-29 17:08:31 -07:00
hive [SPARK-11412][SQL] Support merge schema for ORC 2019-06-29 17:08:31 -07:00
hive-thriftserver [SPARK-28104][SQL] Implement Spark's own GetColumnsOperation 2019-06-22 09:15:07 -07:00
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-27328][SQL] Add 'deprecated' in ExpressionDescription for extended usage and SQL doc 2019-04-09 13:49:42 +08:00
mkdocs.yml
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.