Sunday, September 25, 2016¶

Some ForeignKeys not being protected¶

I discovered and fixed #1183, a subtle problem which might cause unexpected data loss. Changes in The Lino core (the bug itself) and Lino Noi, The Lino Book, Lino Voga (test suites).

The problem was a bug in lino.core.ddh.DisableDeleteHandler.add_fk() : if a model had more than one pointers to a given other model. only the first of them was being collected, the others were ignored. As a consequence, Lino did not replace Django’s default behaviour (cascaded delete) by Lino’s default behaviour (protected) for them.

One symptom was that tickets.Ticket.reporter was not listed below in the output of analyzer.show_foreign_keys(). The following snippets helped to find out why:

>>> for (model, fk) in rt.models.users.User._lino_ddh.fklist:
...     print(fk)
changes.Change.user
clocking.ServiceReport.user
clocking.Session.user
excerpts.Excerpt.user
faculties.Competence.user
outbox.Mail.user
stars.Star.user
tickets.Project.assign_to
tickets.Ticket.assigned_to
tinymce.TextFieldTemplate.user
users.Authority.user

>>> for f in rt.models.tickets.Ticket._meta.get_fields():
...     if f.name == 'reporter':
...         print(repr(f))
<django.db.models.fields.related.ForeignKey: reporter>


On Lino Welfare production sites running a version older than today it is recommended to be careful when deleting users, places, countries, persons and companies. Because if no database object points to a user via the “first” pointer, then Lino would silently delete database objects which point to that user, place, person or company using another pointer.

In order to evaluate the urgence of upgrading here is a list of the most important disable_delete_handlers which were not being installed :

• users.User : aids.Granting.signer, aids.IncomeConfirmation.signer, aids.RefundConfirmation.signer, aids.SimpleConfirmation.signer, art61.Contract.user_asd, cal.Event.assigned_to, immersion.Contract.user_asd, isip.Contract.user_asd, jobs.Contract.user_asd, users.Authority.authorized
• countries.Country : pcsw.Client.birth_country
• contacts.Person: aids.RefundConfirmation.doctor, art61.Contract.contact_person, art61.Contract.signer2

Which means that the danger is rather theoretical. No reason to panic. But I made an unrequested upgrade in CPAS de Châtelet to be sure. In ÖSHZ Eupen I must wait for their decision.

Lino Welfare failure on Travis¶

Build #38 is failing because lino_xl.lib.cal.ui.EventsByDay sorts the events by start_date and start_time, and when two events have the same value for both fields, the result is unpredictable. To fix this, we might simply add the primary key:

order_by = ['start_date', 'start_time', 'id']