GitHub user wangyum opened a pull request:
https://github.com/apache/spark/pull/23028
[SPARK-26053][SQL] Enhance LikeSimplification
## What changes were proposed in this pull request?
This PR enhance `LikeSimplification` in 2 cases:
1. null like col -> null
2. 'str' like col -> col = 'str'
It difficult to handle these cases:
1. 'str%' like col
2. '%str' like col
3. 'str%str' like col
4. '%' like col
for example:
```sql
select '8%' like '8%'; -- true
select '8%' like '%8%'; -- true
select '8%' like '%%8%%'; -- true
select '8%' like '%%5%%8%%'; --false
select '%8' like '%8%'; -- true
select '%8' like '%8%'; -- true
select '%8' like '%%8%'; -- true
select '%8' like '%%5%%8%'; -- false
select '%' like '%'; -- true
select '%' like '%%'; -- true
select '%' like '%%8%'; -- false
```
## How was this patch tested?
unit tests
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/wangyum/spark SPARK-26053
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/23028.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 #23028
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commit 56a02eaaa63f297d3dbaf0ca183e4248d4882834
Author: Yuming Wang <yumwang@...>
Date: 2018-11-14T02:55:25Z
Enhance LikeSimplification
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