GitHub user jinxing64 opened a pull request:
https://github.com/apache/spark/pull/18713
[SPARK-21509][SQL] Add a config to enable adaptive query execution only for
the last queâ¦
## What changes were proposed in this pull request?
Feature of adaptive query execution is a good way to avoid generating too
many small files on HDFS, like mentioned in SPARK-16188.
When feature of adaptive query execution is enabled, all shuffles will be
coordinated. The drawbacks:
1. It's hard to balance the num of reducers(this decides the processing
speed) and file size on HDFS
2. It generates some more
shuffles(https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/EnsureRequirements.scala#L101)
3. It generates lots of jobs, which have extra cost for scheduling.
We can add a config and enable adaptive query execution only for the last
shuffle.
## How was this patch tested?
Unit test.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/jinxing64/spark SPARK-21509
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18713.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 #18713
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commit efb8cd36de0e0b96a8efe855b6243c1f553ce195
Author: jinxing <jinxing6...@126.com>
Date: 2017-07-22T04:22:36Z
Add a config to enable adaptive query execution only for the last query
execution.
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