GitHub user JoshRosen reopened a pull request:
https://github.com/apache/spark/pull/7334
[SPARK-8964] [SQL] [WIP] Use Exchange to perform shuffle in Limit
Spark SQL's physical Limit operator currently performs its own shuffle
rather than using Exchange to perform the shuffling. This is less efficient
since this non-exchange shuffle path won't be able to benefit from SQL-specific
shuffling optimizations, such as SQLSerializer2. It also involves additional
unnecessary row copying.
Instead, I think that we should rewrite Limit to expand into three physical
operators:
PerParititonLimit -> Exchange to one partition -> PerPartitionLimit
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/JoshRosen/spark remove-copy-in-limit
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/7334.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 #7334
----
commit dfe6ff100ae2efcb1778d93bf828f9e2e8c46e18
Author: Josh Rosen <[email protected]>
Date: 2015-07-09T22:27:05Z
Use Exchange in Limit (SPARK-8964)
commit 089f9f5e3153009c35761cde7057af9abcea518c
Author: Josh Rosen <[email protected]>
Date: 2015-07-13T23:13:12Z
Merge remote-tracking branch 'origin/master' into remove-copy-in-limit
commit c02324ca36ad7a9cf8df00246d27f6fbfa61b7c0
Author: Josh Rosen <[email protected]>
Date: 2015-07-13T23:31:12Z
Use requiredChildDistribution in Limit
commit 70f69b63cfa561e84370fe2553d3f5570ceb488f
Author: Josh Rosen <[email protected]>
Date: 2015-07-13T23:58:21Z
Fix test compilation
commit 272c349394f6c53a42c621dce68fc840bcdfac16
Author: Josh Rosen <[email protected]>
Date: 2015-07-16T00:02:57Z
CollectLimit
commit 964838f2b5eb58da06afa18f77a056753e71defc
Author: Josh Rosen <[email protected]>
Date: 2015-07-16T00:55:07Z
Fix test
commit cc634566bdaed630c5bfff887f74defd003b4a58
Author: Josh Rosen <[email protected]>
Date: 2015-07-16T01:05:45Z
Insert ReturnAnswer before calling physical planner
commit 7dbb28e8fd49d670a3dba02b9470a6b10f8589c3
Author: Josh Rosen <[email protected]>
Date: 2015-07-16T01:14:43Z
Fix style
commit 9668c26d1d1ca0f56754353a90f56decd3d8e626
Author: Josh Rosen <[email protected]>
Date: 2015-07-16T01:50:12Z
Merge remote-tracking branch 'origin/master' into remove-copy-in-limit
commit 7202e89c7729ea200bb2d1320985e60c93cc968f
Author: Josh Rosen <[email protected]>
Date: 2015-07-21T01:38:38Z
Merge remote-tracking branch 'origin/master' into remove-copy-in-limit
commit fc7fe5680d81e964c7fc5a22c30aaa0dc837a854
Author: Josh Rosen <[email protected]>
Date: 2016-02-03T19:51:37Z
Merge remote-tracking branch 'origin/master' into remove-copy-in-limit
----
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