GitHub user sameeragarwal opened a pull request:
https://github.com/apache/spark/pull/1048
[SPARK-2042] Prevent unnecessary shuffle triggered by take()
This PR implements `take()` on a `SchemaRDD` by inserting a logical limit
that is followed by a `collect()`. This is also accompanied by adding a
catalyst optimizer rule for collapsing adjacent limits. Doing so prevents an
unnecessary shuffle that is sometimes triggered by `take()`.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/sameeragarwal/spark master
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/1048.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 #1048
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commit 8d42d0308338d0b584a2a1c1e5e89d6ee2c18938
Author: Sameer Agarwal <[email protected]>
Date: 2014-06-11T00:22:57Z
Implement trigger() as limit() followed by collect()
Implement trigger() as limit() followed by collect()gdfg
commit a0ff7c45d2d92367a36365c59377c3c7e2e730d2
Author: Sameer Agarwal <[email protected]>
Date: 2014-06-11T00:26:11Z
Adding catalyst rule to fold two consecutive limits
Creating a LimitFolding Batch
ssdg
commit 8f946a2002b10f0531ccfa5accd5b683a5e98808
Author: Sameer Agarwal <[email protected]>
Date: 2014-06-11T06:09:50Z
Added limit folding tests
Adding tests
Refactoring
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