DurationField stores certain values incorrectly in sqlite

[chausner]

When encoding certain timedelta values in a DurationField, saving the object to a sqlite database and then reading it again, DurationField returns None.

class Foo(models.Model):
    bar = models.DurationField()

Foo.objects.create(bar=timedelta(seconds=2.05))
Foo.objects.create(bar=timedelta(seconds=3.05))

print str(Foo.objects.all()[0].bar) # 'None'
print str(Foo.objects.all()[1].bar) # '3.05'

I can reproduce this bug with Django 1.8.5 and 1.9.3 using sqlite as database backend. It does not occur with MySQL, so it seems to be related to how sqlite stores bigints. It renders DurationField essentially useless with sqlite.

[Tim Graham]

​Problem seems to be in parse_duration(). It can't parse the resulting value and so converts it to None.

Accepting as a release blocker due to possible data corruption. Regression test attached.

[chausner]

Not sure if it's of any help but this bug report here looks related: ​https://github.com/potatolondon/djangae/issues/512.

[Neraste]

I am currently running into the very same problem (Django 1.8.6).

The get_db_prep_value method of DurationField class always returns a float to the database:

return value.total_seconds() * 1000000

Analyzing Django debug logs shows the SQLite driver always receive float values. Some are harmless (eg: 119019000.0), others are harmfull (eg: 133592000.00000001). The last ones come from the funny side effects of floating computation:

>>> 133.592 * 1000000
133592000.00000001

I think it can be fixed with:

return int(round(value.total_seconds() * 1000000))

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In 4f0cd0fd:

Fixed #26324 -- Fixed DurationField with fractional seconds on SQLite.

[Tim Graham <timograham@…>]

In 5b6c7512:

[1.9.x] Fixed #26324 -- Fixed DurationField with fractional seconds on SQLite.

Backport of 4f0cd0fd162122da96978b357ac9fc9534529410 from master

[Tim Graham <timograham@…>]

In c7764ca3:

[1.8.x] Fixed #26324 -- Fixed DurationField with fractional seconds on SQLite.

Backport of 4f0cd0fd162122da96978b357ac9fc9534529410 from master