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Wenchen Fan cded421aeb [SPARK-27871][SQL] LambdaVariable should use per-query unique IDs instead of globally unique IDs 
## What changes were proposed in this pull request?

For simplicity, all `LambdaVariable`s are globally unique, to avoid any potential conflicts. However, this causes a perf problem: we can never hit codegen cache for encoder expressions that deal with collections (which means they contain `LambdaVariable`).

To overcome this problem, `LambdaVariable` should have per-query unique IDs. This PR does 2 things:
1. refactor `LambdaVariable` to carry an ID, so that it's easier to change the ID.
2. add an optimizer rule to reassign `LambdaVariable` IDs, which are per-query unique.

## How was this patch tested?

new tests

Closes #24735 from cloud-fan/dataset.

Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: gatorsmile <gatorsmile@gmail.com>
2019-06-27 11:34:47 -07:00
..
catalyst [SPARK-27871][SQL] LambdaVariable should use per-query unique IDs instead of globally unique IDs 2019-06-27 11:34:47 -07:00
core [SPARK-27871][SQL] LambdaVariable should use per-query unique IDs instead of globally unique IDs 2019-06-27 11:34:47 -07:00
hive [SPARK-28108][SQL][test-hadoop3.2] Simplify OrcFilters 2019-06-24 12:23:52 +08:00
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 [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.