In QGIS, when you connect to a PostgreSQL server, you may notice that multiple connections are established. This behavior is normal and is a result of how QGIS interacts with the database server.

The reason for multiple connections is primarily due to the way QGIS handles various tasks and interactions with the PostgreSQL server. Here are some common scenarios that can lead to multiple connections:

  1. GUI Interactions: QGIS provides a graphical user interface (GUI) that allows users to perform various operations, such as loading layers, editing features, and running queries. Each interaction with the database may require a separate connection.

  2. Rendering and Styling: When rendering maps in QGIS, it needs to retrieve data from the database to display the map features. Different layers and styles may require separate connections to fetch the data efficiently.

  3. Editing and Transactions: QGIS supports editing geospatial data, which often involves using transactions. Each editing session or transaction may establish its connection to manage data changes.

  4. Parallel Processing: QGIS may utilize parallel processing to speed up certain operations, such as data queries. Each parallel process may establish its connection to the database.

  5. Connection Pooling: To manage multiple connections efficiently, QGIS may use connection pooling. Connection pooling helps reuse existing connections rather than creating new ones for each task.

Multiple connections in QGIS are generally not a concern for most use cases, as modern database servers are designed to handle multiple connections efficiently. However, it's essential to ensure that you have an appropriate configuration for your PostgreSQL server to handle the expected number of connections.

If you want to limit the number of connections made by QGIS to the PostgreSQL server, you can adjust the connection pool settings or limit the number of parallel processing tasks in QGIS preferences. However, keep in mind that reducing the number of connections may impact performance, especially when working with large datasets or complex maps.

In summary, multiple connections in QGIS to a PostgreSQL server are normal and allow the application to efficiently manage various tasks and interactions with the database. It's essential to have an appropriately configured database server to handle the expected number of connections and to optimize the performance of your QGIS projects.

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