What means error "Changes to this form will not be saved. 1 field does not meet its constraints."

Question

I just updated to QGIS 3.20. Now I can no longer do multiple updates, due to a constraint at the field ID. I changed the constraint of ID but the problem stays.

I do can make changes when I select objects in the map.

Answer 1

I had the same problem once. In my case I had placed a constraint on what values a field can contain.

Check the field you're trying to give a new value to, go to the form view of the layer and check if you have placed any constraints on that field. In my case for example it was a "radius" field that I had once decided should not take a value of more than 8. Hope your issue is as simple this one.

Edit Just realized the field you had issues with was an id field, could be a case of null or duplicates in the id field? Null should be easy to find, for duplicates check this nifty technique: Identifying duplicate attributes in field using QGIS?

Answer 2

Same issue. Had to revert to 3.16.x. Problem gone.

Answer 3

I just ran into the same problem, on a 3.26.0-Buenos Aires QGIS.

It took me some time to figure it out, but finally, all I had to do was to explicitly add a primary key to the table.

In psql (or any other decent SQL interface to the PostgreSQL server), this did the trick:

ALTER TABLE table_that_i_want_to_edit_in_qgis ADD PRIMARY KEY (id);
-- (provided that id is actually a SERIAL or something
--  equivalent, a unique identifier for the table 
--  table_that_i_want_to_edit_in_qgis)

After that, I was able to edit attributes, modify geometries, etc. in QGIS.

Answer 4

Bug fixed and have to be OK in QGIS 3.26.2.