GitHub user brkyvz opened a pull request:
https://github.com/apache/spark/pull/18364
[SPARK-21153] Use project instead of expand in tumbling windows
## What changes were proposed in this pull request?
Time windowing in Spark currently performs an Expand + Filter, because
there is no way to guarantee the amount of windows a timestamp will fall in, in
the general case. However, for tumbling windows, a record is guaranteed to fall
into a single bucket. In this case, doubling the number of records with Expand
is wasteful, and can be improved by using a simple Projection instead.
## How was this patch tested?
Existing unit tests. Benchmark numbers coming up
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/brkyvz/spark opt-tumble
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18364.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 #18364
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commit 0aab47f52ee44eb75e065a70c1587956e36c6629
Author: Burak Yavuz <[email protected]>
Date: 2017-06-20T16:03:45Z
use project instead of expand in tumbling windows
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