GitHub user mgaido91 opened a pull request:
https://github.com/apache/spark/pull/21133
[SPARK-24013][SQL] Remove unneeded compress in ApproximatePercentile
## What changes were proposed in this pull request?
`ApproximatePercentile` contains a workaround logic to compress the samples
since at the beginning `QuantileSummaries` was ignoring the compression
threshold. This problem was fixed in SPARK-17439, but the workaround logic was
not removed. So we are compressing the samples many more times than needed:
this could lead to critical performance degradation.
## How was this patch tested?
added UT
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/mgaido91/spark SPARK-24013
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/21133.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 #21133
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commit 0ac3b4f1ffe05f51abfb58810c385a4daae016c9
Author: Marco Gaido <marcogaido91@...>
Date: 2018-04-23T20:40:06Z
[SPARK-24013][SQL] Remove unneeded compress in ApproximatePercentile
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