How to use Query Monitor plugin

This guide explains how to use the Query Monitor plugin, a powerful tool for identifying performance issues in your WordPress website. Whether the problem lies in database queries, plugin compatibility, or theme conflicts, Query Monitor can help pinpoint the root cause.

Debugging a Slow Website with Query Monitor

To get started, install the Query Monitor plugin. Once activated, additional information will appear in the admin bar at the top of your WordPress dashboard:

Performance issues can stem from various sources, such as:

• Sitewide problems
• Specific page issues
• Particular functions or actions

Whatever the issue, replicate the problem while Query Monitor is active. The plugin will display detailed diagnostics, helping you identify the cause:

Steps for Diagnosing Issues with Query Monitor

1. Visit the problematic page or trigger the action causing slow performance while Query Monitor is enabled.
2. Examine the diagnostics displayed in Query Monitor to identify errors or bottlenecks.
3. Focus on the reported issues, such as:
   • PHP Errors
   • Database query delays
   • Slow hooks or functions

Example: Diagnosing a Plugin/Theme Conflict

Here’s an example of how Query Monitor helped resolve a plugin/theme conflict:

1. Enabled Query Monitor and visited the problematic page.
2. Query Monitor displayed:
   • PHP Errors (6)
   • A “Doing It Wrong” warning (1)
     
3. The PHP Errors pointed to two problematic plugins:
   • password-protected
   • wc-dynamic-pricing-and-discounts

4. After disabling these plugins (the site was running PHP 8.2), the errors and warnings disappeared.
5. Downgraded the PHP version from 8.2 to 7.4, and no further PHP errors occurred, confirming the plugins were incompatible with PHP 8.2.

As a result, the website loaded significantly faster after resolving the plugin compatibility issues.

Additional Notes

If the issue persists, consider reviewing database queries or enabling the Staq Query Tool for deeper diagnostics. For more guidance on analyzing database queries, check out our guide on using the Staq Query Tool.