GitHub user wzhfy opened a pull request:
https://github.com/apache/spark/pull/17438
[SPARK-20104][SQL] Don't estimate IsNull or IsNotNull predicates for
non-leaf node
## What changes were proposed in this pull request?
In current stage, we don't have advanced statistics such as sketches or
histograms. As a result, some operator can't estimate `nullCount` accurately.
E.g. left outer join estimation does not accurately update `nullCount`
currently. So for `IsNull` and `IsNotNull` predicates, we only estimate them
when the child is a leaf node, whose `nullCount` is accurate.
## How was this patch tested?
A new test case is added in `FilterEstimationSuite`.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/wzhfy/spark nullEstimation
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/17438.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 #17438
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commit 62a8ae514ee22e73e88d8e399a03dcf74195d4de
Author: wangzhenhua <[email protected]>
Date: 2017-03-27T03:22:22Z
don't estimate IsNull or IsNotNull for non-leaf node
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