[MDEV-32816] Make "show collations" data not-nullable Created: 2023-11-15  Updated: 2023-11-24  Resolved: 2023-11-24

Status: Closed
Project: MariaDB Server
Component/s: Protocol
Affects Version/s: None
Fix Version/s: N/A

Type: Bug Priority: Minor
Reporter: Tuomas Hietanen Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None

Issue Links:
Duplicate
duplicates MDEV-31608 MySQL.Data can not connect to MariaD... Closed
Problem/Incident
is caused by MDEV-27009 Add UCA-14.0.0 collations Closed

 Description   

MariaDb returns some nulls as collation info.
That crashes the .Net MySql driver and Oracle os not willing to fix their driver.
–
On connect, the driver tries to load collations IDs and cast them to
integers.
However collation is nullable and there are some null-collations, for
example:

+--------------------------------+----------+------+---------+----------+---------+
 
| Collation                      | Charset  | Id   | Default | Compiled
 
| Sortlen |
 
+--------------------------------+----------+------+---------+----------+---------+
 
 
 
| uca1400_ai_ci                  | NULL     | NULL | NULL    | Yes     
|       8 |
 
| uca1400_ai_cs                  | NULL     | NULL | NULL    | Yes     
|       8 |
 
| uca1400_as_ci                  | NULL     | NULL | NULL    | Yes     
|       8 |
 
| uca1400_as_cs                  | NULL     | NULL | NULL    | Yes     
|       8 |

So the driver fails to connect the database:
InvalidCast_FromDBNull: Object cannot be cast from DBNull to other
types.

Driver has the following code:

                MySqlCommand mySqlCommand = new MySqlCommand("SHOW COLLATION",
 
connection);
 
                try
 
                {
 
                        using MySqlDataReader mySqlDataReader =
 
mySqlCommand.ExecuteReader();
 
                        CharacterSets = new Dictionary<int, string>();
 
                        while (mySqlDataReader.Read())
 
                        {
 
                                CharacterSets[Convert.ToInt32(mySqlDataReader["id"],
 
NumberFormatInfo.InvariantInfo)] =
 
mySqlDataReader.GetString(mySqlDataReader.GetOrdinal("charset"));
 
                        }
 
                }
 
                catch (Exception ex)
 
                {
 
                        MySqlTrace.LogError(ThreadID, ex.Message);
 
                        throw;
 
                }

–
See e.g.: https://bugs.mysql.com/bug.php?id=109331

 Comments   
Comment by Daniel Black [ 2023-11-16 ]

Is there a reason the https://github.com/mysql-net/MySqlConnector and MariaDB Connector/J are unacceptable solutions?

Comment by Vladislav Vaintroub [ 2023-11-21 ]

danblack, I do not think we can force anyone to MySqlConnector no matter how good it is, the Oracle's connector remains slightly more popular.
It is not a drop-in, and people may depend on other open source or closed source software, which happened to use Oracle's connector
Also, as we promised client compatibity, I think we should try to keep this promise

I tried to collect some links on the internet for this issue , it is in MDEV-31608 . We broke OnlyOffice, PowerBI, Toad, and some other stuff with NULL collation ids (something that nobody uses, and something that could be put into a dedicated table).

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