QField use main-detail tables from PostGIS/PostgreSQL

Question

We are using QField for field data collection (forest survey). Our data is stored in a PostGIS/PostgreSQL database and we use QFieldSync to export and import data. This works fine as long, as we use data, that is stored in a single table. During normalization of our database, we had to split up the original survey table into tree tables, one main table containing the static data of the site (including the geometry) and two detail tables (survey and planned actions) that are linked by an 1:many relation to the main table. In QGIS we can use the Data-driven Input Mask-plugin to work with the 3 tables. This seems to work quite well (after our first tests). But we don't know how to archive this in QField?

On way would be to go back to our original flat all-in-one table just for field survey and import the new data later to the 3 tables in the database. Another way would be to create a huge view from the 3 tables and work with the view in the field. The view could then be imported to update the underlying tables (would need to create Trigger in order to make the view updatable).

But may be there is another more elegant and reliable path to follow, since it should be a common problem.

Answer 1

I only use file based data, not PostGIS, but for file based data, you can set-up 1 to many relations. For instance I capture photos for trees, and the photos are in the child table of a 1:n relationship. Working the other way I think you can use the Relation reference to view data of the parent record when editing or viewing a child record. My set-up for child photos is as follows: Parent Table [trees] has field [id] Child Table [Photos] has field [ID] and [treeID], the latter being the foreign key. Set up the one to many relationship in Project Properties, with [tree].[ID] referencing [photos].[treeID]. In the trees form, drag the relation widget into the form and set cardinality to one to many.

Answer 2

@Oisin Hi, I was really curios if that could work with offline date from an PostGIS layer (but it should). I set up the 1:n relations (as association) in my project and they showed up in the attribute form of the parent layer in QGIS. When I tried to add child-datasets in QGIS, PostGIS refuses to save them. In QField I got the same behavior. I can save the parent dataset, but I cannot add a child datasets. I get an error that 'Parent primary keys are not available'.