Database

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  1. Database

A database is a fundamental component of any MediaWiki installation, and understanding its role is crucial for anyone administering or significantly modifying a wiki. This article provides a beginner-friendly introduction to databases, specifically in the context of MediaWiki. We will cover what a database is, why MediaWiki uses one, the common database types used with MediaWiki, key concepts, and basic administration tasks.

What is a Database?

At its core, a database is an organized collection of structured information, or data, stored electronically in a computer system. Think of it like a highly organized electronic filing cabinet. Instead of paper files, it stores data in a structured manner, allowing for efficient retrieval, modification, and deletion of information. Without a database, MediaWiki would be unable to remember articles, user accounts, revisions, or any of the complex data that makes a wiki functional.

Traditional methods of data storage, like text files or spreadsheets, become inefficient and difficult to manage as the volume of data grows. Databases offer several advantages over these methods:

  • **Data Integrity:** Databases enforce rules to ensure the accuracy and consistency of data.
  • **Data Security:** They provide mechanisms to control access to data, protecting it from unauthorized modification or deletion.
  • **Data Efficiency:** Data is stored and retrieved efficiently, even with large datasets.
  • **Data Scalability:** Databases can be scaled to handle increasing amounts of data and user traffic.
  • **Concurrency:** Multiple users can access and modify data simultaneously without causing conflicts (with appropriate database management system features).

Why Does MediaWiki Use a Database?

MediaWiki is a complex application. It needs to store a vast amount of information, including:

  • **Article Content:** The text, wikicode, and formatting of every page.
  • **Revision History:** Every change made to every page, allowing for rollback and comparison.
  • **User Accounts:** Usernames, passwords (hashed, not stored in plain text), email addresses, and user preferences.
  • **Categories:** The categorization structure of the wiki.
  • **Images and Files:** Information about uploaded media files.
  • **Watchlists:** Which pages users are tracking for changes.
  • **Templates:** Reusable content blocks.
  • **Interwiki Links:** Links to other wikis.
  • **And much more...**

Storing all of this data in simple text files would be incredibly slow, inefficient, and prone to errors. A database provides a reliable and efficient way to manage this complex data. MediaWiki relies heavily on the database for all of its core functionality. The speed and efficiency of the database directly impact the performance of the wiki. Understanding Database performance is therefore key.

Common Database Types Used with MediaWiki

MediaWiki supports several database management systems (DBMS). Here are the most common:

  • **MySQL/MariaDB:** This is the most widely used database for MediaWiki. MariaDB is a fork of MySQL, and often considered a drop-in replacement. Both are relational databases, meaning data is organized into tables with rows and columns. They are known for their reliability, performance, and extensive community support. MySQL optimization is a frequently discussed topic.
  • **PostgreSQL:** Another popular relational database, PostgreSQL is known for its adherence to SQL standards and its advanced features, such as support for complex data types and transactions. It’s often preferred for wikis that require high data integrity or complex queries. PostgreSQL tuning is important for large wikis.
  • **SQLite:** A lightweight, file-based database. SQLite is often used for small wikis, testing environments, or single-user installations because it doesn't require a separate server process. However, it's not suitable for high-traffic wikis because it has limitations in concurrency and scalability.
  • **Oracle:** A commercial relational database known for its scalability and security. While MediaWiki *can* run on Oracle, it's less common due to the cost and complexity.

The choice of database depends on several factors, including:

  • **Wiki Size:** Larger wikis require more robust databases like MySQL/MariaDB or PostgreSQL.
  • **Traffic Volume:** High-traffic wikis need databases that can handle concurrent connections.
  • **Budget:** Oracle is a commercial database that requires a license fee.
  • **Technical Expertise:** Some databases require more specialized knowledge to administer.

Key Database Concepts

Understanding these concepts will help you grasp how MediaWiki interacts with the database:

  • **Relational Database:** As mentioned, MySQL, MariaDB, PostgreSQL, and Oracle are relational databases. Data is organized into tables, and relationships between tables are defined using keys. This structure promotes data integrity and efficient querying.
  • **Table:** A collection of related data organized in rows and columns. For example, a `user` table might store information about each user account.
  • **Row (Record):** A single entry in a table. For example, a row in the `user` table would represent a single user.
  • **Column (Field):** A specific attribute of a row. For example, the `user` table might have columns for `user_id`, `username`, `email`, and `password`.
  • **SQL (Structured Query Language):** The standard language for interacting with relational databases. MediaWiki uses SQL to retrieve, insert, update, and delete data. Learning basic SQL queries is very helpful for troubleshooting.
  • **Schema:** The structure of the database, including the tables, columns, and relationships between them. MediaWiki has a predefined schema that must be set up correctly.
  • **Database Server:** The software that manages the database. Examples include the MySQL server, PostgreSQL server, etc.
  • **Database Client:** A program used to connect to the database server and execute SQL queries. Examples include phpMyAdmin, DBeaver, and command-line tools.
  • **Index:** A data structure that improves the speed of data retrieval. Indexes are created on columns that are frequently used in queries. However, excessive indexing can slow down write operations. Database indexing strategies are crucial.
  • **Transaction:** A sequence of database operations that are treated as a single unit of work. Transactions ensure that either all operations succeed, or none of them do, maintaining data consistency.

Basic Database Administration Tasks

While a systems administrator typically handles these tasks, understanding them is helpful for wiki maintainers.

  • **Database Creation:** Creating a new database specifically for MediaWiki.
  • **User Management:** Creating database users with appropriate permissions to access the MediaWiki database. *Never* use the root database user for MediaWiki.
  • **Backup and Restore:** Regularly backing up the database to protect against data loss. Restoring the database from a backup in case of failure. Automated database backup scripts are highly recommended.
  • **Database Updates:** Applying updates and patches to the database server to fix bugs and improve security.
  • **Performance Monitoring:** Monitoring database performance to identify and resolve bottlenecks. Tools like MySQLTuner or pgAdmin can help. Analyzing database query performance is key.
  • **Schema Updates:** Applying schema changes when upgrading MediaWiki. MediaWiki provides scripts to automate these updates.
  • **Database Repair:** Running database repair tools to fix corruption issues.

Connecting MediaWiki to the Database

MediaWiki is configured to connect to the database through the `LocalSettings.php` file. The following settings are essential:

```php $wgDBtype = 'mysql'; // or 'postgres', 'sqlite', 'oracle' $wgDBserver = 'localhost'; // or the database server's hostname $wgDBname = 'your_wiki_database'; // The name of your database $wgDBuser = 'your_wiki_user'; // The database username $wgDBpassword = 'your_wiki_password'; // The database password $wgDBport = 3306; // Default MySQL port, adjust if necessary ```

    • Important Security Note:** Never hardcode database passwords directly into `LocalSettings.php` in a production environment. Consider using environment variables or a more secure configuration management system.

Troubleshooting Database Issues

Common database-related errors in MediaWiki include:

  • **"Can't connect to MySQL server on 'localhost'..."**: Indicates a problem with the database server being down, incorrect credentials, or network connectivity.
  • **"Error: Database error..."**: A generic error message indicating a problem with an SQL query. Check the MediaWiki error logs for more details.
  • **Slow Page Loads:** Often caused by slow database queries. Use database profiling tools to identify and optimize slow queries. Consider implementing database caching strategies.
  • **Database Locking:** Occurs when multiple processes attempt to access the same database resources simultaneously. Can be resolved by optimizing queries or increasing database server resources.
  • **Database Corruption:** Can lead to data loss or unpredictable behavior. Restore from a recent backup.

Advanced Database Topics

  • **Database Replication:** Creating multiple copies of the database to improve performance and availability.
  • **Database Clustering:** Combining multiple database servers to create a single, highly scalable database system.
  • **Database Sharding:** Partitioning the database into smaller, more manageable shards.
  • **Full-Text Search:** Using database features to enable efficient searching of article content. Elasticsearch integration provides advanced full-text search capabilities.
  • **Database Auditing:** Tracking changes to the database for security and compliance purposes.
  • **Database normalization:** Organizing data to reduce redundancy and improve data integrity. Database normalization techniques are vital for efficiency.

Resources

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MediaWiki configuration MediaWiki administration LocalSettings.php Database performance SQL queries Database indexing strategies Database backup scripts Database query performance Database caching Full-text search capabilities Database normalization techniques

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