MySQL Workbench で MariaDB に接続時のエラー「テーブル 'performance_schema.user_variables_by_thread' が存在しません」の解決策

MySQL WorkbenchでMariaDBに接続時のエラー「テーブル 'performance_schema.user_variables_by_thread' が存在しません」の解決策

MySQL Workbenchを使用してMariaDBに接続しようとすると、以下のエラーが発生することがあります。

Error loading schema content
Error Code: 1146
Table 'performance_schema.user_variables_by_thread' doesn't exist

このエラーは、MySQL Workbench 8.0.16以降でMariaDB 10.xに接続する場合に発生することが多いようです。

原因

このエラーの原因は、MySQL Workbench 8.0.16以降で、MariaDB 10.xで使用されなくなったテーブルperformance_schema.user_variables_by_threadを参照しようとするためです。

解決策

この問題を解決するには、以下のいずれかの方法を試してください。

MySQL Workbenchをダウングレードする

MySQL Workbench 8.0.15以前のバージョンを使用すると、この問題は発生しません。古いバージョンのMySQL Workbenchは、MySQL Workbenchダウンロードページ からダウンロードできます。

MariaDB 10.5以降にアップグレードする

MariaDB 10.5以降では、performance_schema.user_variables_by_threadテーブルが削除されており、この問題は発生しません。

• Workbenchの接続設定で「パフォーマンススキーマ」を無効にする

  1. MySQL Workbenchを起動し、MariaDBに接続します。
  2. 「サーバー管理」>「接続」に移動します。
  3. 使用している接続をクリックし、「編集」ボタンをクリックします。
  4. 「詳細」タブをクリックします。
  5. 「パフォーマンススキーマ」オプションを無効にします。
  6. 「OK」をクリックして保存します。

DROP TABLE performance_schema.user_variables_by_thread;

注意事項

• 上記の回避策を使用する前に、MariaDBのバックアップを取っておくことをお勧めします。
• performance_schema.user_variables_by_threadテーブルは、パフォーマンスの監視に使用されるため、削除する前に影響がないことを確認してください。

import mysql.connector

# Database connection parameters
db_host = "localhost"
db_user = "root"
db_password = "password"
db_name = "your_database_name"

# Establish a connection to the MariaDB server
try:
    connection = mysql.connector.connect(
        host=db_host,
        user=db_user,
        password=db_password,
        database=db_name
    )
    print("Connected to MariaDB server successfully")

except mysql.connector.Error as e:
    print("Failed to connect to MariaDB server:", e)

# Use the connection to execute queries and perform operations
cursor = connection.cursor()
cursor.execute("SELECT * FROM your_table")
results = cursor.fetchall()

for row in results:
    print(row)

# Close the database connection
connection.close()

This code first imports the mysql.connector module, which is used to connect to MariaDB. Then, it defines the database connection parameters, including the host, username, password, and database name.

Next, it attempts to establish a connection to the MariaDB server using the connect() function. If the connection is successful, it prints a message to the console. If the connection fails, it catches the mysql.connector.Error exception and prints an error message.

Once connected, the code creates a cursor object, which is used to execute queries and perform operations on the database. It then executes a SELECT query to retrieve all rows from the your_table table and stores the results in a variable.

Finally, it iterates over the results and prints each row to the console. Before exiting, it closes the database connection using the close() method.

Please note that you may need to modify the connection parameters to match your specific environment. For example, if you are connecting to a remote MariaDB server, you will need to specify the server's hostname or IP address. Additionally, if you are using a different username or password, you will need to update those values accordingly.

Please let me know if you have any other questions.

Using SSH Tunneling

If you need to connect to a remote MariaDB server that is not accessible directly from your local machine, you can use SSH tunneling to establish a secure connection through an intermediate SSH server. Here's a general overview of the steps involved:

1. • Install an SSH client on your local machine if you haven't already.
   • Configure the SSH client to connect to the intermediate SSH server.
   • Establish an SSH tunnel to forward traffic from your local machine to the remote MariaDB server.

2. Connect MySQL Workbench:

   • Launch MySQL Workbench and create a new connection.
   • In the connection settings, select "Standard TCP/IP over SSH" as the connection method.
   • Provide the SSH server's hostname or IP address, SSH username, and SSH port number.
   • Specify the remote MariaDB server's hostname or IP address and port number.
   • Enter the MariaDB username and password.
   • Test the connection to ensure it's successful.

Using a Cloud-Based Solution

If you are using a cloud-hosted MariaDB instance, you may be able to connect to it using a cloud-based solution provided by your cloud provider. For example, Amazon Web Services (AWS) offers Amazon RDS for MariaDB, which provides a management console and API for connecting to your MariaDB instances. Similarly, Google Cloud Platform (GCP) offers Cloud SQL for MariaDB, which also provides a management console and API for connecting to your MariaDB instances.

Using a Command-Line Tool

If you prefer using command-line tools, you can connect to MariaDB using the mysql command-line client. The mysql client is included in most Linux distributions and can be installed on Windows and macOS using third-party packages. To connect to MariaDB using the mysql client, use the following command:

mysql -u username -p -h hostname -P port -D database_name

Replace username with your MariaDB username, hostname with the MariaDB server's hostname or IP address, port with the MariaDB server's port number (default: 3306), and database_name with the name of the database you want to connect to. When prompted, enter your MariaDB password.

These are just a few alternative methods for connecting to MariaDB using MySQL Workbench. The best method for you will depend on your specific requirements and environment.