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Wenchen Fan 4a9c9d8f9a [SPARK-25159][SQL] json schema inference should only trigger one job 
## What changes were proposed in this pull request?

This fixes a perf regression caused by https://github.com/apache/spark/pull/21376 .

We should not use `RDD#toLocalIterator`, which triggers one Spark job per RDD partition. This is very bad for RDDs with a lot of small partitions.

To fix it, this PR introduces a way to access SQLConf in the scheduler event loop thread, so that we don't need to use `RDD#toLocalIterator` anymore in `JsonInferSchema`.

## How was this patch tested?

a new test

Closes #22152 from cloud-fan/conf.

Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: Xiao Li <gatorsmile@gmail.com>
2018-08-21 22:21:08 -07:00
..
catalyst [SPARK-25159][SQL] json schema inference should only trigger one job 2018-08-21 22:21:08 -07:00
core [SPARK-25159][SQL] json schema inference should only trigger one job 2018-08-21 22:21:08 -07:00
hive Fix typos detected by github.com/client9/misspell 2018-08-11 21:23:36 -05:00
hive-thriftserver [SPARK-25043] print master and appId from spark-sql on startup 2018-08-14 13:15:55 -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.