Data export options

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  1. Data Export Options

This article details the various data export options available within a MediaWiki 1.40 installation. Understanding these options is crucial for data backup, migration, analysis, and integration with external systems. Whether you're a wiki administrator, a developer, or a data analyst, this guide provides a comprehensive overview of the tools and methods at your disposal. We will cover built-in functionality, extensions, and considerations for large-scale data exports.

Introduction

MediaWiki stores its data primarily within a relational database, typically MySQL/MariaDB, PostgreSQL, or SQLite. Direct database access is the most comprehensive, but often requires technical expertise and can be risky if not handled correctly. MediaWiki also provides several built-in and extension-based methods for exporting data in more accessible formats. These methods range from simple page content downloads to complex database dumps suitable for full wiki replication. The choice of export method depends on your specific needs. Considerations include the volume of data, the desired format, the level of technical skill available, and the purpose of the export. Before initiating any export, it is *highly* recommended to create a full database backup. This is covered in Manual:Backups and is essential for disaster recovery.

Built-in Export Functionality

MediaWiki includes several built-in features for exporting data without relying on extensions. These are generally suitable for smaller-scale exports, such as individual pages or specific revisions.

Page Exports

The most basic export option is to download the content of individual pages. This can be done by viewing a page and selecting "Export" from the "More" dropdown menu (usually located near the "Watch" and "Edit" buttons). This option downloads the page content in WikiText format, along with any embedded images (as links to the files). This method is useful for moving content to other wikis or for archiving individual articles. It’s not ideal for large-scale exports due to the manual nature of the process.

Special:Export

The `Special:Export` page provides a more advanced, though still limited, export capability. This special page allows you to export multiple pages at once, selecting them by title or using wildcard characters. You can also choose to include the page's history, categories, and embedded files. The export is generated as an XML file containing the WikiText and associated metadata. This is a significantly better option than individual page exports for moving a collection of related articles. However, it still has limitations regarding the size of the export and the complexity of the data.

  • **Namespace Selection:** `Special:Export` allows you to specify which namespaces to include in the export. This is useful for exporting only articles, templates, or other specific types of pages.
  • **History Inclusion:** Including history significantly increases the size of the export file. Consider whether you actually need the full revision history before enabling this option.
  • **File Inclusion:** Exporting files along with the WikiText can be useful, but it also increases the file size and may require careful consideration of licensing and copyright issues.

API Access

The MediaWiki API (Application Programming Interface) provides programmatic access to wiki data. While more complex to use, the API allows for highly customized and automated data exports. You can use the API to retrieve page content, revision history, category membership, and other information. The API is typically accessed using programming languages like Python, PHP, or JavaScript. It’s a powerful tool for developers who need to integrate MediaWiki data with external applications or create custom export scripts. See Manual:API for detailed documentation. Using the API often involves implementing rate limiting to avoid overloading the wiki server.

Extensions for Enhanced Data Export =

Several extensions extend MediaWiki's data export capabilities, providing more advanced features and formats.

XML Dump

The `XMLDump` extension is a popular choice for creating full or partial database dumps in XML format. It generates a large XML file containing all or a subset of the wiki's data, including pages, revisions, users, and categories. The XMLDump extension is particularly useful for creating backups, migrating wikis, and replicating data to other servers. It requires significant server resources, especially for large wikis. See [1](https://www.mediawiki.org/wiki/Extension:XMLDump) for more information.

  • **Partial Dumps:** The extension supports partial dumps, allowing you to export only specific namespaces or articles. This can significantly reduce the size of the dump file.
  • **Compression:** XML dumps can be compressed using gzip to reduce storage space and transfer time.
  • **Database Locking:** The XMLDump extension typically requires locking the database during the dump process. This can impact wiki availability, so it's best to perform dumps during off-peak hours.

Database Dumps (mysqldump, pg_dump)

Directly accessing the database and creating a dump using tools like `mysqldump` (for MySQL/MariaDB) or `pg_dump` (for PostgreSQL) is the most comprehensive way to export all wiki data. This method requires database administrator privileges and a good understanding of the database schema. It produces a SQL file that can be used to restore the database on another server. This is the preferred method for full wiki backups and migrations. See [2](https://www.mysql.com/doc/refman/8.0/en/mysqldump.html) and [3](https://www.postgresql.org/docs/current/app-pgdump.html) for documentation.

  • **Consistency:** Ensure database consistency before creating a dump. This may involve locking the database or using replication to create a consistent snapshot.
  • **Large Databases:** For very large databases, consider using incremental backups or logical replication to reduce the time and resources required for the dump.
  • **Security:** Protect the database dump file, as it contains sensitive data.

WikiData Extension

The `WikiData` extension allows you to export data in RDF (Resource Description Framework) format, which is a standard for representing knowledge in a machine-readable way. This is useful for integrating MediaWiki data with semantic web applications and knowledge graphs. See [4](https://www.mediawiki.org/wiki/Extension:WikiData) for more information. RDF is particularly useful for complex relationships between data points.

Other Extensions

Numerous other extensions offer specialized data export capabilities. These include extensions for exporting data to CSV, JSON, or other formats. Search the MediaWiki Extension Directory ([5](https://www.mediawiki.org/wiki/Extension_directory)) for extensions that meet your specific needs.

Data Formats and Their Uses

The choice of export format depends on the intended use of the data.

  • **WikiText:** Suitable for migrating content between wikis or for archiving individual articles.
  • **XML:** Versatile format for storing structured data. Useful for backups, migrations, and data integration.
  • **SQL:** The standard format for database backups and restores.
  • **RDF:** Ideal for representing knowledge in a machine-readable way and integrating with semantic web applications.
  • **CSV:** Simple format for tabular data. Useful for importing data into spreadsheets or other applications.
  • **JSON:** Popular format for data exchange. Useful for web applications and APIs.

Considerations for Large-Scale Exports

Exporting large amounts of data from a MediaWiki installation can be challenging. Here are some considerations:

  • **Server Resources:** Large exports can consume significant server resources, including CPU, memory, and disk space. Ensure your server has sufficient capacity to handle the load.
  • **Database Locking:** Some export methods require locking the database, which can impact wiki availability. Schedule exports during off-peak hours.
  • **Timeouts:** Long-running exports may be interrupted by timeouts. Increase timeout settings in your PHP configuration or use asynchronous processing.
  • **Compression:** Compress the export files to reduce storage space and transfer time.
  • **Incremental Exports:** For very large wikis, consider using incremental exports to minimize the impact on performance.
  • **Rate Limiting:** When using the API, implement rate limiting to avoid overloading the wiki server.
  • **Data Integrity:** Verify the integrity of the exported data to ensure it is accurate and complete.

Security Considerations

  • **Database Credentials:** Protect database credentials used for direct database access.
  • **Export File Security:** Securely store and transmit export files, as they may contain sensitive data.
  • **Access Control:** Restrict access to export tools and data to authorized users only.

Troubleshooting Export Issues

  • **Check Error Logs:** Review the MediaWiki error logs for any error messages related to the export process.
  • **Increase PHP Memory Limit:** Increase the PHP memory limit in your php.ini file if you encounter memory-related errors.
  • **Increase Execution Time:** Increase the PHP execution time limit if the export process times out.
  • **Verify Database Connection:** Ensure that MediaWiki can connect to the database.
  • **Test with a Small Subset:** Test the export process with a small subset of data before attempting a full export.

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