GitHub user wangyum opened a pull request:
https://github.com/apache/spark/pull/18138
[SPARK-20915][SQL] Make lpad/rpad with empty pad string same as MySQL.
## What changes were proposed in this pull request?
Spark SQL `rpad/lpad` with empty pad string:
```sql
spark-sql> select rpad('hello', -2, ''), rpad('hello', -1, '') ,
rpad('hello', 0, ''), rpad('hello', 1, ''), rpad('hello', 3, ''), rpad('hello',
5, ''), rpad('hello', 6, '');
h hel hello hello
spark-sql> select lpad('hello', -2, ''), lpad('hello', -1, '') ,
lpad('hello', 0, ''), lpad('hello', 1, ''), lpad('hello', 3, ''), lpad('hello',
5, ''), lpad('hello', 6, '');
h hel hello hello
spark-sql>
```
but the MySQL result:
```
mysql> select rpad('hello', -2, ''), rpad('hello', -1, '') , rpad('hello',
0, ''), rpad('hello', 1, ''), rpad('hello', 3, ''), rpad('hello', 5, ''),
rpad('hello', 6, '') from dual;
+-----------------------+-----------------------+----------------------+----------------------+----------------------+----------------------+----------------------+
| rpad('hello', -2, '') | rpad('hello', -1, '') | rpad('hello', 0, '') |
rpad('hello', 1, '') | rpad('hello', 3, '') | rpad('hello', 5, '') |
rpad('hello', 6, '') |
+-----------------------+-----------------------+----------------------+----------------------+----------------------+----------------------+----------------------+
| NULL | NULL | | h
| hel | hello | NULL
|
+-----------------------+-----------------------+----------------------+----------------------+----------------------+----------------------+----------------------+
1 row in set (0.00 sec)
mysql> select lpad('hello', -2, ''), lpad('hello', -1, '') , lpad('hello',
0, ''), lpad('hello', 1, ''), lpad('hello', 3, ''), lpad('hello', 5, ''),
lpad('hello', 6, '') from dual;
+-----------------------+-----------------------+----------------------+----------------------+----------------------+----------------------+----------------------+
| lpad('hello', -2, '') | lpad('hello', -1, '') | lpad('hello', 0, '') |
lpad('hello', 1, '') | lpad('hello', 3, '') | lpad('hello', 5, '') |
lpad('hello', 6, '') |
+-----------------------+-----------------------+----------------------+----------------------+----------------------+----------------------+----------------------+
| NULL | NULL | | h
| hel | hello | NULL
|
+-----------------------+-----------------------+----------------------+----------------------+----------------------+----------------------+----------------------+
1 row in set (0.01 sec)
```
This PR fix this issue, after this PR:
```sql
spark-sql> select rpad('hello', -2, ''), rpad('hello', -1, '') ,
rpad('hello', 0, ''), rpad('hello', 1, ''), rpad('hello', 3, ''), rpad('hello',
5, ''), rpad('hello', 6, '');
NULL NULL h hel hello NULL
spark-sql> select lpad('hello', -2, ''), lpad('hello', -1, '') ,
lpad('hello', 0, ''), lpad('hello', 1, ''), lpad('hello', 3, ''), lpad('hello',
5, ''), lpad('hello', 6, '');
NULL NULL h hel hello NULL
spark-sql>
```
## 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-20915
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18138.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 #18138
----
commit 3ac9fb07ef2f53315247ad12d391b1bed92319e9
Author: Yuming Wang <wgy...@gmail.com>
Date: 2017-05-29T16:47:55Z
Make lpad/rpad with empty pad string same as MySQL.
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