Github user HyukjinKwon commented on the issue:
https://github.com/apache/spark/pull/18142
I am leaving a note (at least to myself) since it looked anyhow caused
behaviour change.
With this statements in Hive side:
```sql
CREATE TABLE emp AS SELECT 'user' AS name, 'address' as address;
CREATE DATABASE d100;
CREATE FUNCTION d100.udf100 AS
'org.apache.hadoop.hive.ql.udf.generic.GenericUDFUpper';
```
**Hive**
```
hive> SELECT d100.udf100(`emp`.`name`) FROM `emp`;
USER
hive> SELECT `d100.udf100`(`emp`.`name`) FROM `emp`;
USER
```
**Spark**
Before:
```
scala> spark.sql("SELECT d100.udf100(`emp`.`name`) FROM `emp`").show
+-----------------+
|d100.udf100(name)|
+-----------------+
| USER|
+-----------------+
scala> spark.sql("SELECT `d100.udf100`(`emp`.`name`) FROM `emp`").show
+-----------------+
|d100.udf100(name)|
+-----------------+
| USER|
+-----------------+
```
After:
```
scala> spark.sql("SELECT d100.udf100(`emp`.`name`) FROM `emp`").show
+-----------------+
|d100.udf100(name)|
+-----------------+
| USER|
+-----------------+
scala> spark.sql("SELECT `d100.udf100`(`emp`.`name`) FROM `emp`").show
org.apache.spark.sql.AnalysisException: Undefined function: 'd100.udf100'.
This function is neither a registered temporary function nor a permanent
function registered in the database 'default'.; line 1 pos 7
```
**MySQL**
This change causes a inconsistency with Hive although looks consistent
compating to MySQL.
```
mysql> SELECT `d100.udf100`(`emp`.`name`) FROM `emp`;
ERROR 1305 (42000): FUNCTION hkwon.d100.udf100 does not exist
mysql> SELECT d100.udf100(`emp`.`name`) FROM `emp`;
+---------------------------+
| d100.udf100(`emp`.`name`) |
+---------------------------+
| Hello, user! |
+---------------------------+
1 row in set (0.01 sec)
```
---
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
