GitHub user ron8hu opened a pull request:
https://github.com/apache/spark/pull/19783
support histogram in filter cardinality estimation
## What changes were proposed in this pull request?
Histogram is effective in dealing with skewed distribution. After we
generate histogram information for column statistics, we need to adjust filter
estimation based on histogram data structure.
## How was this patch tested?
We revised all the unit test cases by including histogram data structure.
Please review http://spark.apache.org/contributing.html before opening a
pull request.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ron8hu/spark supportHistogram
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/19783.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 #19783
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commit dd5b975dafdf9fc4edd94cf6e369f5e899db74e2
Author: Ron Hu <ron...@huawei.com>
Date: 2017-11-19T19:37:47Z
support histogram in filter cardinality estimation
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