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API:Query debugger

## API: Query Debugger

Overview

The API:Query debugger is a powerful tool integrated within MediaWiki 1.40 (and available in earlier versions with varying degrees of functionality) designed to assist developers and administrators in troubleshooting and optimizing complex API queries. It provides a detailed, step-by-step analysis of query execution, revealing bottlenecks, errors, and inefficient code. This is particularly valuable when working with large datasets, complex filtering criteria, or custom extensions that interact with the MediaWiki database. The debugger doesn’t alter the live database; it provides a read-only analysis of the query plan and execution. Understanding how the API:Query debugger operates is crucial for maintaining a healthy and responsive MediaWiki installation, especially on a dedicated server. It’s a fundamental element in ensuring that your wiki's API functions smoothly under load. The tool allows you to inspect the generated SQL, execution times for each stage, and other critical performance metrics. This article provides a comprehensive overview of the API:Query debugger, its specifications, use cases, performance considerations, and its pros and cons. This tool is essential for anyone managing a high-traffic wiki or developing custom API integrations. It complements tools like phpMyAdmin for database administration by focusing specifically on API query performance. It can be accessed through a special URL parameter added to API requests.

Specifications

The API:Query debugger relies on several underlying components within the MediaWiki architecture. Its functionality is intrinsically linked to the Database layer and the Parser. Below is a detailed specification table outlining key aspects of the debugger.

Feature Description Value Requirements
Debugger Name Tool for analyzing API query execution. API:Query Debugger MediaWiki 1.20+ (functionality varies)
Activation Method URL parameter added to API requests. `&debug=query` Requires appropriate permissions
Data Output Format Structured data displaying query execution details. JSON, XML, or raw SQL (configurable). Depends on API request format.
Key Metrics Reported Detailed timings for each stage of query execution. SQL parsing, query planning, data retrieval, result formatting. N/A
Database Support Compatible with all supported MediaWiki databases. MySQL/MariaDB, PostgreSQL, SQLite. Database connection must be valid.
Security Considerations Access restricted by user permissions. Requires `debug` permission. Proper configuration is crucial.
Configuration Location Defined in `LocalSettings.php`. `$wgDebugLogGroups` and related settings. Access to server configuration files.
API Endpoint Targeted Any API endpoint that executes database queries. `api.php` N/A

The debugger’s effectiveness is also dependent on the underlying server hardware and network configuration. A slow disk I/O or limited memory can significantly impact query performance and, consequently, the accuracy of the debugger's analysis. It's important to remember that the `API:Query debugger` analyzes the *planned* execution of the query, as well as the *actual* execution. This distinction is critical for identifying discrepancies between expected and observed performance.

Use Cases

The API:Query debugger has a wide range of applications for MediaWiki administrators and developers. Here are a few key use cases:

⚠️ *Note: All benchmark scores are approximate and may vary based on configuration. Server availability subject to stock.* ⚠️