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oraviv fcf66a3276 [SPARK-21657][SQL] optimize explode quadratic memory consumpation 
## What changes were proposed in this pull request?

The issue has been raised in two Jira tickets: [SPARK-21657](https://issues.apache.org/jira/browse/SPARK-21657), [SPARK-16998](https://issues.apache.org/jira/browse/SPARK-16998). Basically, what happens is that in collection generators like explode/inline we create many rows from each row. Currently each exploded row contains also the column on which it was created. This causes, for example, if we have a 10k array in one row that this array will get copy 10k times - to each of the row. this results a qudratic memory consumption. However, it is a common case that the original column gets projected out after the explode, so we can avoid duplicating it.
In this solution we propose to identify this situation in the optimizer and turn on a flag for omitting the original column in the generation process.

## How was this patch tested?

1. We added a benchmark test to MiscBenchmark that shows x16 improvement in runtimes.
2. We ran some of the other tests in MiscBenchmark and they show 15% improvements.
3. We ran this code on a specific case from our production data with rows containing arrays of size ~200k and it reduced the runtime from 6 hours to 3 mins.

Author: oraviv <oraviv@paypal.com>
Author: uzadude <ohad.raviv@gmail.com>
Author: uzadude <15645757+uzadude@users.noreply.github.com>

Closes #19683 from uzadude/optimize_explode.
2017-12-29 21:08:34 +08:00
..
catalyst [SPARK-21657][SQL] optimize explode quadratic memory consumpation 2017-12-29 21:08:34 +08:00
core [SPARK-21657][SQL] optimize explode quadratic memory consumpation 2017-12-29 21:08:34 +08:00
hive [SPARK-22834][SQL] Make insertion commands have real children to fix UI issues 2017-12-29 15:28:33 +08:00
hive-thriftserver [MINOR][BUILD] Fix Java linter errors 2017-12-28 09:43:50 -06:00
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 [SPARK-21485][SQL][DOCS] Spark SQL documentation generation for built-in functions 2017-07-26 09:38:51 -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.

Running sql/create-docs.sh generates SQL documentation for built-in functions under sql/site.