Hi Brylie, Laurence,
I think it should be possible to do this using my Check Constraints work
(https://github.com/django/django/pull/7615) or something built on top
of it.
I plan to get this work into shape so it can land in Django 2.1.
I hope this helps,
Ian
On 03/10/17 10:40, Laurence Sonnenberg wrote:
> A pythonic way to do this would be extremely useful if it existed. As
> you suggested, I did this using a sql exclusion constraint statement on
> the table and a migration.
>
> For example:
>
> 000x_your_migration_name.py
>
> # -*- coding: utf-8 -*-
> from __future__ import unicode_literals
>
> from django.db import migrations
>
> SQL = """ALTER TABLE your_table DROP CONSTRAINT IF EXISTS
> range_overlap_exclusion;
> ALTER TABLE your_table ADD CONSTRAINT range_overlap_exclusion
> EXCLUDE USING gist (resource WITH =, date_range WITH &&);"""
>
>
> class Migration(migrations.Migration):
>
> dependencies = [
> ('module_name', '000x_previous_migration'),
> ]
>
> operations = [migrations.RunSQL(sql=SQL,
> reverse_sql=migrations.RunSQL.noop), ]
>
>
> On Sunday, October 1, 2017 at 11:53:53 PM UTC+2, Brylie Christopher
> Oxley wrote:
>
> Now that Django supports the DateRangeField, is there a 'Pythonic'
> way to prevent records from having overlapping date ranges?
>
> # Hypothetical use case
> One hypothetical use case would be a booking system, where you don't
> want people to book the same resource at the same time.
>
> # Hypothetical example code
> <!-- language: lang-py -->
>
> class Booking(models.model):
> # The resource to be reserved
> resource = models.ForeignKey('Resource')
> # When to reserve the resource
> date_range = models.DateRangeField()
>
> class Meta:
> unique_together = ('resource', 'date_range',)
>
> This might have the effect of adding an exclusion constraint on the
> underlying table:
>
> https://www.postgresql.org/docs/9.3/static/sql-createtable.html#SQL-CREATETABLE-EXCLUDE
>
> <https://www.postgresql.org/docs/9.3/static/sql-createtable.html#SQL-CREATETABLE-EXCLUDE>
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.
>
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