[Qgis-user] Using relations and transaction groups

[Matthias Kuhn]

Hi Rhys,

Ironically, this situation is exactly what transaction mode has been 
added for (to avoid the situation where someone clicks the save windows 
button before the save footprint button).

The solution is not that obvious though (and might be poorly 
documented): Enable "deferred constraint checks" in your database and it 
will only check if foreign key constraints are ok at commit time (when 
you save it) and not while editing. If by any chance you get around to 
adding this information into the documentation, this will be much 
appreciated!

Bests

Matthias

On 3/3/20 6:23 AM, Rhys A.D. Stewart wrote:
> Greetings All,
>
> I'm working with transaction groups and tables with relations 
> (database foreign keys). Let's say that there are two tables, 
> 'building_footprints'  and 'windows'. The windows table references the 
> 'building_footprints' table. I've added the relations in QGIS through 
> the Project properties | relations dialog so that when editing 
> 'building_footprints' I can add a child record for 'windows'. Now 
> because I have transaction groups active, the changes are pushed back 
> to the database immediately, if I create a child record before saving 
> the parent record this causes a problem because the parent record 
> doesn't exist. It is often the case that I am going to add child 
> records when I'm creating the parent record, so adding a parent 
> record, saving it, then editing it just to add the child record 
> becomes cumbersome.
>
> I figured that someone must've had this issue before, but can't seem 
> to find any documentation about this. Is there a workaround for this? 
> (other than not using transaction groups and saving each layer 
> individually)  Or have I just missed something extremely obvious?
>
>
> Rhys
> Peace & Love | Live Long & Prosper
>
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