Prevent DateRangeField overlap in model?

[Brylie Christopher Oxley]

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
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[Laurence Sonnenberg]

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), ]

[Ian Foote]

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

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