Why Does an Exception Occur When I Drop Functions Created Using the Add Jar Statement?

Question

Problem 1
Why can I successfully drop functions without the drop function permission? The specific scenario is as follows:
1. On the FusionInsight Manager console, I added the user1 user and granted the admin permission to the user1 user.
```
set role admin;add jar /home/smartcare-udf-0.0.1-SNAPSHOT.jar;create database db4;use db4;create function f11 as 'com.huaweixxx.smartcare.dac.hive.udf.UDFArrayGreaterEqual';create function f12 as 'com.huaweixxx.smartcare.dac.hive.udf.UDFArrayGreaterEqual';
```
2. I canceled the admin permission of the user1 user and ran the following command:
```
drop functiondb4.f11;
```
The result shows that the drop is successful, as shown in Figure 1.
Figure 1 Command output of the drop function command
Problem 2
After the preceding operation, I ran the show function command and the command output indicates that the function still exits. The specific scenario is as follows:
1. On the FusionInsight Manager console, I added the user1 user and granted the admin permission to the user1 user. Then I ran following commands in spark-beeline:
```
set role admin;create database db2;use db2;add jar /home/smartcare-udf-0.0.1-SNAPSHOT.jar;create function f11 as 'com.huaweixxx.smartcare.dac.hive.udf.UDFArrayGreaterEqual';create function f12 as 'com.huaweixxx.smartcare.dac.hive.udf.UDFArrayGreaterEqual';
```
2. I exited and re-logged in to spark-beeline and ran the following command:
```
set role admin;use db2;drop function db2.f11;
```
3. I exited and re-logged in to spark-beeline and ran the following command:
```
use db2;show functions;
```
The command output indicates that function still exists, as shown in Figure 2.

Figure 2 Output of the show functions command

Answer

Root cause:
The root cause is that, in multi-active instance mode or multi-tenant mode, the function created using the add jar command in spark-beeline is invisible to JDBCServer instances. When you run the drop function command, if the JDBCServer instance connected by the session is not the JDBCServer instance that creates the function, the function cannot be found in the session. In addition, the default value of hive.exec.drop.ignorenonexistent in Hive is true. Therefore, if function does not exist, no exception is reported when the deleting function operation is performed. As a result, no exception is reported when you delete a non-existing function and perform drop operation even though you do not have the drop function permission. When you run the show function command after restarting the session and connecting to the JDBCServer instance that creates the function, the command output indicates that the function still exists. This problem is inherited from the Hive community.
Solution
Before running drop function command, run the add jar command. In this way, the drop operation succeeds only when you are granted the drop function permission, and the dropped function will not be displayed if you run the show function command.