Enables the range_merge Aggregate for Django on Postgres
Project description
django-range-merge
Enables the range_merge Aggregate for Django on Postgres. range_merge "Computes the smallest range that includes ... the given ranges".
This package should only be used with Django projects using the Postgres database. See Postgres docs on Range Functions.
Note: This app is still a work-in-progress, but currently works. Tests have not yet been implemented.
Installing
Add to INSTALLED_APPS:
INSTALLED_APPS = [
...
"django_range_merge",
...
]
Migrate to apply the aggregation to your database:
> python manage.py migrate
Getting Started
Here is a quick example. We have an Event model with two different range fields: period, which contains the datetime range period during which the Event occurs; and potential_visitors, which is an approximation of the minimum and maximum number of people attending the Event.
We want two different views to help Event organizers understand some aggregate details about Events.
- range_of_visitors_this_month: Show the overall lowest and greatest number of people we expect for all events this month
- overall_dates_of_funded_events: Shows the overall range of dates for Events which are funded (the
is_fundedBooleanField is set to True)
models.py
class Event(models.Model):
name = models.CharField(max_length=30)
period = models.DateTimeRangeField(help_text="The period of time this event covers")
potential_visitors = models.IntegerRangeField(help_text="The range of visitors expected at this event")
is_funded = BooleanField(default=False)
class Meta:
verbose_name = "Event"
verbose_name_plural = "Events"
def __str__(self):
return self.name
date_utils.py (get a range covering the entire current month)
from django.utils import timezone
from dateutil.relativedelta import relativedelta
from psycopg2.extras import DateTimeTZRange
def get_month_range():
"""Return a DateTimeRange range covering this entire month"""
today = timezone.now().date()
if today.day > 25:
today += timezone.timedelta(7)
this_month_start = today.replace(day=1)
next_month_start = this_month_start + relativedelta(months=1)
return DateTimeTZRange(this_month_start, next_month_start)
views.py
from django.db.models import F, Aggregate
from django.template.response import TemplateResponse
from .date_utils import get_month_range
def range_of_visitors_this_month(request):
"""
e.g., given the following instances:
{"id" : 1, "name" : "Birthday", "potential_visitors" : "[2, 3)", ...}
{"id" : 2, "name" : "Bake Sale", "potential_visitors" : "[30, 50)", ...}
{"id" : 3, "name" : "Band Camp", "potential_visitors" : "[22, 28)", ...}
{"id" : 4, "name" : "Cooking Show", "potential_visitors" : "[7, 20)", ...}
{"id" : 5, "name" : "Pajama Day", "potential_visitors" : "[15, 30)", ...}
The result would be:
{'output': NumericRange(2, 50, '[)')}
"""
template = "base.html"
context = Event.objects.filter(period__overlap=get_month_range()).aggregate(
output=Aggregate(F("potential_visitors"), function="range_merge")
)
return TemplateResponse(request, template, context)
def overall_dates_of_funded_events(request):
template = "base.html"
context = Event.objects.filter(is_funded=True).aggregate(
output=Aggregate(F("period"), function="range_merge")
)
# Example result: {'output': DateTimeRange("2022-10-01 02:00:00", "2022-12-07 12:00:00", '[)')}
return TemplateResponse(request, template, context)
base.html
<html>
<head></head>
<body>
{{ output }}
</body>
</html>
License
The code in this repository is licensed under The MIT License. See LICENSE.md in the repository for more details.
Contributing
Contributions are very welcome.
This project is currently accepting all types of contributions, bug fixes, security fixes, maintenance work, or new features. However, please make sure to have a discussion about your new feature idea with the maintainers prior to beginning development to maximize the chances of your change being accepted. You can start a conversation by creating a new issue on this repo summarizing your idea.
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