GitHub user dilipbiswal opened a pull request:
https://github.com/apache/spark/pull/13368
SPARK-15557] expression ((cast(99 as decimal) + '3') * '2.3' ) return NULL
In this case, the result type of the expression becomes DECIMAL(38, 36) as
we promote the individual string literals to DECIMAL(38, 18) when we handle
string promotions for `BinaryArthmaticExpression`.
I think we need to cast the string literals to Double type instead. I
looked at the history and found that this was changed to use decimal instead
of double to avoid potential loss of precision when we cast decimal to double.
To double check i ran the query against hive, mysql. This query returns non
NULL result for both the databases and both promote the expression to use
double.
Here is the output.
- Hive
```SQL
hive> create table l2 as select (cast(99 as decimal(19,6)) + '2') from l1;
OK
hive> describe l2;
OK
_c0 double
```
- MySQL
```SQL
mysql> create table foo2 as select (cast(99 as decimal(19,6)) + '2') from
test;
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> describe foo2;
+-----------------------------------+--------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra
|
+-----------------------------------+--------+------+-----+---------+-------+
| (cast(99 as decimal(19,6)) + '2') | double | NO | | 0 |
|
+-----------------------------------+--------+------+-----+---------+-------+
```
## How was this patch tested?
Added a new test in SQLQuerySuite
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dilipbiswal/spark spark-15557
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/13368.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 #13368
----
commit 46f34955cd076c376b43bb262be1cff9754c8285
Author: Dilip Biswal <dbis...@us.ibm.com>
Date: 2016-05-27T22:35:37Z
SPARK-15557] expression ((cast(99 as decimal) + '3') * '2.3' ) return null
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