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| author | Eric Moyer <eric_moyer@yahoo.com> | 2015-01-08 11:55:23 -0800 |
|---|---|---|
| committer | Andrew Or <andrew@databricks.com> | 2015-01-08 11:55:23 -0800 |
| commit | 538f221627930c8f8a138c0d21d9fa09bc789e67 (patch) | |
| tree | 9622c9db88df2da47bcce752e51b3f77e19c1e1e /bagel/pom.xml | |
| parent | 0760787da885187b0c6dcd5c28753f0ab014d5ed (diff) | |
| download | spark-538f221627930c8f8a138c0d21d9fa09bc789e67.tar.gz spark-538f221627930c8f8a138c0d21d9fa09bc789e67.tar.bz2 spark-538f221627930c8f8a138c0d21d9fa09bc789e67.zip | |
Document that groupByKey will OOM for large keys
This pull request is my own work and I license it under Spark's open-source license.
This contribution is an improvement to the documentation. I documented that the maximum number of values per key for groupByKey is limited by available RAM (see [Datablox][datablox link] and [the spark mailing list][list link]).
Just saying that better performance is available is not sufficient. Sometimes you need to do a group-by - your operation needs all the items available in order to complete. This warning explains the problem.
[datablox link]: http://databricks.gitbooks.io/databricks-spark-knowledge-base/content/best_practices/prefer_reducebykey_over_groupbykey.html
[list link]: http://apache-spark-user-list.1001560.n3.nabble.com/Understanding-RDD-GroupBy-OutOfMemory-Exceptions-tp11427p11466.html
Author: Eric Moyer <eric_moyer@yahoo.com>
Closes #3936 from RadixSeven/better-group-by-docs and squashes the following commits:
5b6f4e9 [Eric Moyer] groupByKey docs naming updates
238e81b [Eric Moyer] Doc that groupByKey will OOM for large keys
Diffstat (limited to 'bagel/pom.xml')
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