Filter object by calculating duration from start and end time

[Steven Nash]

Hi,

Given an object such as:

class Entry(models.Model):
  start = models.TimeField()
  end = models.TimeField()

I'd like to be able to say something like:

Entry.objects.filter(F('end')-F('start')__gt=time_in_minutes)

Is there a way of doing this without implementing a separate duration field and having a setter for start and end update it?

Cheers,
Steve

[Simon Charette]

Hi Steve,

You can use annotate for this.

from datetime import timedelta

from django.db.models import DurationField, ExpressionWrapper, F

Entry.objects.annotate(
    duration=ExpressionWrapper(
        F('end') - F('start'), output_field=DurationField()
    )
).filter(duration__gte=timedelta(minutes=time_in_minutes)

Cheers,
Simon

[Xristos Xristoou]

can used this and for the dates fields ?

[Steven Nash]

Hi Simon,

Thanks, I'll give that ago.

Cheers,

Steve

[Simon Charette]

Hi Steve,

It looks like it might only work on PostgreSQL unti this bug is fixed.

Simon

[Steven Nash]

That's fine as am using Postgres on centos 7

Cheers

Steve 

Sent from my iPhone

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