GitHub user JoshRosen opened a pull request:
https://github.com/apache/spark/pull/6773
[SPARK-8319] [CORE] [SQL] Update logic related to key orderings in shuffle
dependencies
This patch updates two pieces of logic that are related to handling of
keyOrderings in ShuffleDependencies:
- The Tungsten ShuffleManager falls back to regular SortShuffleManager
whenever the shuffle dependency specifies a key ordering, but technically we
only need to fall back when an aggregator is also specified. This patch updates
the fallback logic to reflect this so that the Tungsten optimizations can apply
to more workloads.
- The SQL Exchange operator performs defensive copying of shuffle inputs
when a key ordering is specified, but this is unnecessary: SortShuffleManager
is the only shuffle manager that performs sorting on the map side, and it only
does so when an aggregator is specified. SQL never uses Spark's shuffle for
performing aggregation, so this copying is unnecessary.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/JoshRosen/spark SPARK-8319
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/6773.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #6773
----
commit 8467c7e823fd4a76dda0e527b67c743bf531e6db
Author: Josh Rosen <joshro...@databricks.com>
Date: 2015-06-12T01:02:08Z
Enable Tungsten shuffle for non-agg shuffles w/ key orderings
commit dfb8fadf2f3351731620eab6b981b70024a726d4
Author: Josh Rosen <joshro...@databricks.com>
Date: 2015-06-12T01:09:16Z
Avoid unnecessary copy in SQL Exchange
commit 85a46287e2264ff4d736a5feabe1b36becb519af
Author: Josh Rosen <joshro...@databricks.com>
Date: 2015-06-12T01:13:12Z
Update comment to clarify circumstances under which shuffle operates on
serialized records
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