#25339: Aggregation and annotation by time period and intervals (by month, week,
day, hour, etc)
-------------------------------------+-------------------------------------
Reporter: malefice | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: 1.8
(models, ORM) |
Severity: Normal | Resolution:
Keywords: QuerySet.extra | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by malefice):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> I often found that aggregation of data by dynamically generating time
> periods given a desired time interval is a very sought after feature. I
> personally created the snippet below to accommodate my needs, but as per
> the note
> [https://docs.djangoproject.com/en/dev/ref/models/querysets/#django.db.models.query.QuerySet.extra
> here], the extra() method will be deprecated soon. I think it will be a
> waste to deprecate this API, since there is simply a lot of DBMS-specific
> SQL functions available, but if there is any way we can do this via
> Django ORM, then I am still up for it. The snippet below shows a custom
> QuerySet method I often use.
>
> {{{#!python
> def get_metrics(self, frequency):
> select_fields = OrderedDict()
> if frequency == 'week':
> select_fields['time_period'] = "date_trunc(%s,
> initial_timestamp::TIMESTAMP WITH TIME ZONE AT TIME ZONE %s + '1
> day'::interval) - '1 day'::interval"
> else:
> select_fields['time_period'] = "date_trunc(%s,
> initial_timestamp::TIMESTAMP WITH TIME ZONE AT TIME ZONE %s)"
> select_params = (frequency, settings.TIME_ZONE,)
> queryset = self.extra(select=select_fields,
> select_params=select_params).values('time_period', ....)
> queryset = queryset.annotate(
> # Add annotations
> )
> return queryset
> }}}
New description:
I often found that aggregation of data by dynamically generating time
periods given a desired time interval is a very sought after feature. I
personally created the snippet below to accommodate my needs, but as per
the note
[https://docs.djangoproject.com/en/dev/ref/models/querysets/#django.db.models.query.QuerySet.extra
here], the extra() method will be deprecated soon. I think it will be a
waste to deprecate this API, since there is simply a lot of DBMS-specific
SQL functions available, but if there is any way we can do this via Django
ORM, then I am still up for it. The snippet below shows a custom QuerySet
method I often use.
{{{#!python
def get_metrics(self, frequency):
select_fields = OrderedDict()
if frequency == 'week':
select_fields['time_period'] = "date_trunc(%s,
initial_timestamp::TIMESTAMP WITH TIME ZONE AT TIME ZONE %s + '1
day'::interval) - '1 day'::interval"
else:
select_fields['time_period'] = "date_trunc(%s,
initial_timestamp::TIMESTAMP WITH TIME ZONE AT TIME ZONE %s)"
select_params = (frequency, settings.TIME_ZONE,)
queryset = self.extra(
select=select_fields,
select_params=select_params
).values('time_period', ....)
queryset = queryset.annotate(
# Add annotations
)
return queryset
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/25339#comment:1>
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