Content ¶

This piece explores a powerful but underutilized QGIS feature developed by Oslandia that enables automatic layer refreshes triggered by PostgreSQL notifications. The capability became available in QGIS version 3.0.

Core Concept ¶

The article demonstrates implementing PostgreSQL NOTIFY functionality to automatically update QGIS layers when database changes occur, eliminating manual refresh requirements.

Implementation Steps ¶

1. Create a notification function ¶

Create a function that sends NOTIFY signals to QGIS:

• Uses PL/pgSQL language
• Returns trigger type
• Executes NOTIFY qgis command

2. Add database triggers ¶

Add database triggers on INSERT, UPDATE, or DELETE events to invoke the notification function.

3. Enable layer settings ¶

Check the “refresh layer on notification” option in QGIS layer properties.

Practical Application ¶

Users can leave QGIS open and observe new features from other machines automatically displaying without manual intervention.

Related Resources ¶

The author references Oslandia’s detailed documentation covering implementation specifics and triggering custom actions via NOTIFY signals.