[PyQt] Going multiuser with QSqlRelationalTableModel

[Ricardo Araoz]

On 31/03/18 12:37, J Barchan wrote:
> ​
>
> On 30 March 2018 at 16:48, Ricardo Araoz <ricaraoz at gmail.com 
> <mailto:ricaraoz at gmail.com>> wrote:
>
>     Are there any methods for multiuser database programming while
>     working with models and mappers? I mean, something to lock/unlock
>     records and/or tables (not talking about transactions) and
>     something that will tell me when saving if the database records to
>     be updated have been changed since the model read them.
>
>     TIA
>
>
> ​Hi Ricardo,
>
> I am not a PyQt expert person --- just someone using it.
>
> I would say basically "no".  ​QSqlRelationalTableModel is just a thin 
> layer over QSqlTableModel, and that's just QSqlTableQuery/QSqlQuery 
> with some support for putting it in a table and allowing you to 
> specify INSERT/DELETE/UPDATE commands.  Other than that you're really 
> on your own to add your own stuff.
>
> The usual way to handle "multiuser" is to make your DELETE/UPDATE 
> statements do /optimistic /updates, i.e. you add a WHERE clause to 
> verify all the values in the database are the same as when you read 
> the row in, else someone else has changed it and then you error.  
> That's instead of /pessimistic/ locking, where you lock the row when 
> you read it, which doesn't scale.  You could implement these yourself.
>
> Otherwise, this isn't a PyQt/Python question, so if you want to 
> discuss in detail or see if Qt experts have more to offer than I have 
> you might like to join up to https://forum.qt.io/ and come pose your 
> question there.
>
> -- 
> Kindest,
> Jonathan

Hi Jonathan, thanks for your answer. I know I could do it by myself, But 
I'd be missing the automatic behaviour implemented by the 
model/view/delegate schema. I'm now thinking about subclassing the model 
and implementing something in the submit and submitAll methods.
Cheers
Ricardo

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