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Wenchen Fan 9f5647d62e [SPARK-21319][SQL] Fix memory leak in sorter 
## What changes were proposed in this pull request?

`UnsafeExternalSorter.recordComparator` can be either `KVComparator` or `RowComparator`, and both of them will keep the reference to the input rows they compared last time.

After sorting, we return the sorted iterator to upstream operators. However, the upstream operators may take a while to consume up the sorted iterator, and `UnsafeExternalSorter` is registered to `TaskContext` at [here](https://github.com/apache/spark/blob/v2.2.0/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeExternalSorter.java#L159-L161), which means we will keep the `UnsafeExternalSorter` instance and keep the last compared input rows in memory until the sorted iterator is consumed up.

Things get worse if we sort within partitions of a dataset and coalesce all partitions into one, as we will keep a lot of input rows in memory and the time to consume up all the sorted iterators is long.

This PR takes over https://github.com/apache/spark/pull/18543 , the idea is that, we do not keep the record comparator instance in `UnsafeExternalSorter`, but a generator of record comparator.

close #18543

## How was this patch tested?

N/A

Author: Wenchen Fan <wenchen@databricks.com>

Closes #18679 from cloud-fan/memory-leak.
2017-07-27 22:56:26 +08:00
..
catalyst [SPARK-21319][SQL] Fix memory leak in sorter 2017-07-27 22:56:26 +08:00
core [SPARK-21319][SQL] Fix memory leak in sorter 2017-07-27 22:56:26 +08:00
hive [SPARK-10063] Follow-up: remove a useless test related to an old output committer 2017-07-23 21:32:59 +08:00
hive-thriftserver [SPARK-20345][SQL] Fix STS error handling logic on HiveSQLException 2017-06-12 14:05:03 -07:00
create-docs.sh [SPARK-21485][SQL][DOCS] Spark SQL documentation generation for built-in functions 2017-07-26 09:38:51 -07:00
gen-sql-markdown.py [SPARK-21485][SQL][DOCS] Spark SQL documentation generation for built-in functions 2017-07-26 09:38:51 -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.