Database Management

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  1. Database Management for Wiki Administrators and Developers

This article provides a comprehensive overview of Database Management for users of MediaWiki, particularly those involved in administration, development, or advanced content creation. Understanding how MediaWiki interacts with its database is crucial for maintaining performance, ensuring data integrity, and performing complex operations. This guide is geared towards beginners, assuming limited prior database experience.

What is a Database?

At its core, a database is a structured collection of data. Think of it like a highly organized digital filing cabinet. Instead of paper files, information is stored electronically, allowing for efficient retrieval, modification, and deletion. MediaWiki, unlike simple static websites, relies heavily on a database to store *everything*:

  • Page content (the text you see on each wiki page)
  • Revision history (every edit made to a page)
  • User accounts and permissions
  • Category memberships
  • Template data
  • Images and other uploaded files (metadata, not the files themselves)
  • Watchlist information
  • Recent changes data
  • Search index data

Without a database, MediaWiki would be unable to function. Every time you view a page, edit an article, or log in, the wiki is interacting with the database.

MediaWiki and MySQL/MariaDB

MediaWiki is primarily designed to work with MySQL or its popular, open-source fork, MariaDB. These are both Relational Database Management Systems (RDBMS). "Relational" means the data is organized into *tables* with relationships defined between them. This structure is fundamental to understanding how MediaWiki stores information.

While other database systems *can* be used with MediaWiki (PostgreSQL, SQLite), MySQL/MariaDB are the most common and well-supported options. This article will focus on these.

Key Database Concepts

Before delving into specific MediaWiki database operations, let's define some essential terms:

  • **Table:** A collection of related data organized in rows and columns. For example, a `user` table might store information about each registered user.
  • **Column:** A vertical section of a table representing a specific attribute of the data. In the `user` table, columns might include `user_id`, `username`, `email`, and `password`.
  • **Row (or Record):** A horizontal section of a table representing a single instance of the data. Each row in the `user` table represents a single user.
  • **Primary Key:** A column (or set of columns) that uniquely identifies each row in a table. The `user_id` is usually the primary key in the `user` table.
  • **Foreign Key:** A column in one table that refers to the primary key in another table, establishing a relationship between the two tables. For example, a `page` table might have a `user_id` as a foreign key, linking each page to the user who created it.
  • **SQL (Structured Query Language):** The standard language used to communicate with relational databases. You use SQL to retrieve, insert, update, and delete data.
  • **Database Schema:** The overall structure of the database, including all the tables, columns, and relationships. MediaWiki has a predefined schema, but it can be extended with extensions.
  • **Database Server:** The software (MySQL/MariaDB) that manages the database and handles requests from applications like MediaWiki.
  • **phpMyAdmin:** A popular web-based tool for administering MySQL/MariaDB databases. It provides a graphical interface for managing tables, executing SQL queries, and performing other database tasks.

Common MediaWiki Database Tables

Here’s a look at some of the most important tables used by MediaWiki:

  • **`user`:** Stores user account information.
  • **`page`:** Contains information about wiki pages (ID, title, namespace).
  • **`revision`:** Stores the content of each page revision, along with metadata like timestamp and user ID. This is a *very* large table in active wikis.
  • **`text`:** Contains the actual text content of each revision. Often linked to the `revision` table.
  • **`category`:** Stores information about categories.
  • **`categorylink`:** Links pages to categories.
  • **`watchlist`:** Stores the list of pages each user is watching.
  • **`recentchanges`:** A log of recent changes made to the wiki.
  • **`searchindex`:** Contains data used for the wiki's search functionality.

Understanding these tables, and how they relate to each other, is key to troubleshooting issues and performing advanced database operations. Detailed schema information can be found on the MediaWiki wiki under "Database schema".

Basic Database Management Tasks

As a wiki administrator, you might need to perform the following tasks:

  • **Backups:** Regularly backing up the database is *critical*. This protects your data from loss due to hardware failure, software errors, or accidental deletion. phpMyAdmin allows you to export the database as an SQL file. Automated backup solutions are highly recommended. Consider using tools like `mysqldump` for command-line backups.
  • **Restores:** Restoring a database from a backup is essential in case of data loss. phpMyAdmin allows you to import an SQL file.
  • **Database Maintenance:** Regular database maintenance, such as optimizing tables and checking for errors, can improve performance. MySQL/MariaDB provides commands like `OPTIMIZE TABLE` and `CHECK TABLE`.
  • **User Management:** While most user management is done through the MediaWiki interface, you might occasionally need to directly manage user accounts in the database, especially for advanced permissions or troubleshooting.
  • **Troubleshooting:** Understanding the database schema is invaluable when troubleshooting errors. You can use SQL queries to examine data and identify the source of problems.
  • **Schema Modifications (Advanced):** *Caution:* Modifying the database schema directly can be risky and should only be done by experienced developers. Extensions often modify the schema, but it's crucial to understand the implications.

Using phpMyAdmin

phpMyAdmin is a powerful and user-friendly tool for managing your MediaWiki database. Here's a quick overview:

1. **Access phpMyAdmin:** Typically, your web hosting provider will provide access to phpMyAdmin through your hosting control panel (cPanel, Plesk, etc.). 2. **Login:** You'll need the MySQL/MariaDB username and password configured for your MediaWiki installation. 3. **Select the Database:** Once logged in, select the MediaWiki database from the list on the left. 4. **Browse Tables:** You can browse the tables in the database and view their structure and data. 5. **Execute SQL Queries:** Click the "SQL" tab to enter and execute SQL queries. 6. **Import/Export:** Use the "Import" and "Export" tabs to back up and restore the database.

Understanding SQL Queries

Here are some basic SQL queries you might find useful:

  • **`SELECT * FROM user;`**: Retrieves all data from the `user` table.
  • **`SELECT username, email FROM user WHERE user_id = 1;`**: Retrieves the username and email for the user with `user_id` equal to 1.
  • **`INSERT INTO user (username, email, password) VALUES ('newuser', 'newuser@example.com', 'password');`**: Inserts a new user into the `user` table. *Caution: Never store passwords in plain text!*
  • **`UPDATE user SET email = 'newemail@example.com' WHERE user_id = 1;`**: Updates the email address for the user with `user_id` equal to 1.
  • **`DELETE FROM user WHERE user_id = 1;`**: Deletes the user with `user_id` equal to 1. *Caution: This is irreversible!*
  • **`SELECT COUNT(*) FROM revision;`**: Counts the total number of revisions in the `revision` table.

These are just basic examples. SQL is a powerful language with many more features. Numerous online resources are available to learn more about SQL. Refer to the SQL tutorial for more advanced examples.

Optimizing Database Performance

As your wiki grows, database performance can become a concern. Here are some strategies to optimize performance:

  • **Indexing:** Creating indexes on frequently queried columns can significantly speed up data retrieval. MediaWiki automatically creates some indexes, but you might need to add more based on your specific usage patterns.
  • **Caching:** MediaWiki uses caching extensively to reduce the load on the database. Ensure that caching is enabled and configured appropriately. Explore different caching mechanisms like Memcached or Redis.
  • **Database Server Configuration:** Adjusting the MySQL/MariaDB server configuration (e.g., buffer sizes, query cache) can improve performance. This requires advanced knowledge of database administration.
  • **Query Optimization:** Review and optimize slow-running SQL queries. Use the `EXPLAIN` statement in MySQL/MariaDB to analyze query execution plans.
  • **Regular Maintenance:** Perform regular database maintenance tasks, such as optimizing tables and removing unnecessary data.
  • **Hardware:** Ensure that your database server has sufficient resources (CPU, memory, disk I/O) to handle the load.
  • **Database Replication:** For very large wikis, consider using database replication to distribute the load across multiple servers.

Security Considerations

  • **Strong Passwords:** Use strong, unique passwords for your MySQL/MariaDB user accounts.
  • **Limited Privileges:** Grant only the necessary privileges to the MediaWiki user account. Avoid granting it full administrative access.
  • **Database Firewall:** Configure a firewall to restrict access to the database server.
  • **Regular Updates:** Keep your MySQL/MariaDB server and MediaWiki software up to date with the latest security patches.
  • **SQL Injection Prevention:** MediaWiki’s code should protect against SQL injection attacks, but it’s crucial to be aware of this vulnerability and follow secure coding practices when developing extensions.

Resources for Further Learning

Database Administration is a complex topic, but a solid understanding of the fundamentals will empower you to manage your MediaWiki installation effectively.

MediaWiki Configuration

Extensions

Server Administration

Security

Performance Optimization

Database Replication

SQL Injection

Caching

User Rights Management

MediaWiki API

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