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Andy Grove 1012967ace [SPARK-35767][SQL] Avoid executing child plan twice in CoalesceExec 
### What changes were proposed in this pull request?

`CoalesceExec` needlessly calls `child.execute` twice when it could just call it once and re-use the results. This only happens when `numPartitions == 1`.

### Why are the changes needed?

It is more efficient to execute the child plan once rather than twice.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

There are no functional changes. This is just a performance optimization, so the existing tests should be sufficient to catch any regressions.

Closes #32920 from andygrove/coalesce-exec-executes-twice.

Authored-by: Andy Grove <andygrove73@gmail.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
2021-06-15 11:59:21 -07:00
..
catalyst [SPARK-35129][SQL] Construct year-month interval column from integral fields 2021-06-15 19:19:41 +03:00
core [SPARK-35767][SQL] Avoid executing child plan twice in CoalesceExec 2021-06-15 11:59:21 -07:00
hive [SPARK-35321][SQL] Don't register Hive permanent functions when creating Hive client 2021-06-12 10:32:30 +08:00
hive-thriftserver [SPARK-35704][SQL] Add fields to DayTimeIntervalType 2021-06-11 16:16:33 +03:00
create-docs.sh [SPARK-34010][SQL][DODCS] Use python3 instead of python in SQL documentation build 2021-01-05 19:48:10 +09:00
gen-sql-api-docs.py [SPARK-34747][SQL][DOCS] Add virtual operators to the built-in function document 2021-03-19 10:19:26 +09:00
gen-sql-config-docs.py [SPARK-32194][PYTHON] Use proper exception classes instead of plain Exception 2021-05-26 11:54:40 +09:00
gen-sql-functions-docs.py [SPARK-31562][SQL] Update ExpressionDescription for substring, current_date, and current_timestamp 2020-04-26 11:46:52 -07:00
mkdocs.yml
README.md

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 extensions that allow 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, and SQL configuration documentation that gets included as part of configuration.md in the main docs directory.