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QFieldCloud System Documentation

The aim of this document is to provide an overview of the QFieldCloud system to understand the underlaying logic and technology.

Entities and Concepts

QGIS Project

A QGIS project is a .qgs or .qgz file. A Project is created on QGIS Desktop and uploaded to QFieldCloud using the QGIS's plugin QFieldSync. Before the uploading of the QGIS project, it is necessary for each layer of the QGIS project an "action" that determines how QFieldSync and QField should treat the layer. There are the two types of actions that can be setup - one for QFieldCloud and one for the traditional cable export.

This information is saved within the QGS project as layer's customProperty, with the QFieldSync/action key.

The available actions are:

Action internal name Name showed in the UI
OFFLINE Consolidate
NO_ACTION Live layer
REMOVE Ignore layer
COPY Copy
KEEP_EXISTING Keep Existing

This would be the behavior of QFieldSync with the different layer actions:

Action File based layer Not file based layer
OFFLINE Create a consolidated copy of the data Create a consolidated copy of the data
NO_ACTION N/A No action on the layer
REMOVE Remove the layer from the project Remove the layer from the project
COPY Make source path relative and copy the file N/A
KEEP_EXISTING Make source path relative and copy the file if it does not exist N/A

This is the behavior of QFieldCloud (libqfieldsync) with the layers:

Action File based layer Not file based
OFFLINE Create consolidated copy of the data on pull, apply delta file on push to original data source Create consolidated copy of the data on pull, apply delta file on push to original data source
NO_ACTION N/A No action on the layer
REMOVE Remove the layer from the project Remove the layer from the project
COPY Make source path relative and create copy of the data on pull, apply delta file on push to original data source N/A
KEEP_EXISTING Make source path relative and create copy of the data on pull, apply delta file on push to original data source N/A

This is the behavior of QField with the layers:

Action File based layer Not file based layer
OFFLINE Create and push deltafile N/A (it's always file based at this point)
NO_ACTION N/A Edit the online (live) database
REMOVE N/A (the layer is no longer there) N/A (the layer is no longer there)
COPY Create and push deltafile N/A
KEEP_EXISTING Create and push deltafile N/A

In summary, for with QFieldCloud:

  • NO_ACTION is used for online layers that are located on a server accessible via the Internet and that are modified directly by QField.
  • HYBRID means that a geopackage will be generated on the server (or directly on the desktop for file-based layers) and downloaded by clients. The client will generate deltafiles of the changes.
  • OFFLINE is used for example to work with local databases not visible by QFieldCloud which are consolidated before being loaded from the desktop to the server and are not synchronized with the original data by QFieldCloud.
  • REMOVE will simply remove the layer from the project.
  • KEEP_EXISTENT will not be used for QFieldCloud syncronizations.

From QFieldSync it will be possible to update a project already loaded on QFieldCloud. In the event that the changes concern only styles, forms etc. but not the structure of the layers, the project on the server will simply be updated. If there are changes in the layers structure, the project will be reset on the server (delta files will be deleted) and for each client it will be necessary to download the updated version of the project before being able to push new changes.

QFieldCloud Project

Is composed of one and only one QGIS project and the possible
related files (e.g. geopackages, images, ...) included the offline
or hybrid data package.

Use Cases

Hybrid

Hybrid editing mode with synchronization on the server

Hybrid editing mode
Hybrid editing mode

Offline database

Offline editing mode with desktop synchronization

Offline editing mode
Offline editing mode

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