Re: Query annotation with date difference

Sun, 04 Sep 2016 10:35:17 -0700


from django.db.models.functions import Now
.annotate(ratio=(F(‘due_date')-Now())/F('Interval'))

On Aug 3, 2016, at 3:34 PM, Constantine Covtushenko <[email protected]> wrote:

Sorry, I did not specify.
I have been using 'Postgresql' with 'psycopg2 v.2.6.2'.
They gave me those results.

Also here is a sql query given from log:
SELECT "test_app_entity"."id", "test_app_entity"."due_date", "test_app_entity"."interval", (("test_app_entity"."due_date" - '2016-08-03T21:31:58.325549+00:00'::timestamptz) / "test_app_entity"."interval") AS "ratio" FROM "test_app_entity"; args=(datetime.datetime(2016, 8, 3, 21, 31, 58, 325549, tzinfo=<UTC>),)

That is all that I can say at the moment.

On Thu, Aug 4, 2016 at 12:20 AM, Yoann Duriaud <[email protected]> wrote:
Thanks, unfortunately not so great on my side:

I added in the query (forgetting the division for now):

.annotate(ratio=ExpressionWrapper(F('due_date')-timezone.now(), DateTimeField()))


which leads to the following statement in the query:
 
("contentstatus"."due_date" - 2016-08-03 21:05:10.743799+00:00) AS "ratio"


This is not a valid SQL statement (at least for SQLite) and leads to the following error message when the query is evaluated:

Exception Type:

TypeError
Exception Value: 

expected string or bytes-like object

Any idea what I get this behavior?

Yoann


Le samedi 30 juillet 2016 22:41:21 UTC+2, Yoann Duriaud a écrit :
Hello,
I would like to annotate a query with the following _expression_: ([Due Date] - [Now])/[Interval]. [Due Date] and [Interval] are fields from the database, while [Now] should be "equal" to timezone.now().

So this would look like:
.annotate(ratio=(F('due_date')-timezone.now())/F('Interval'))

but this does not work. Does someone know how the _expression_ should be written (if it is indeed feasible with Django ORM)?

Thanks for your help!

Yoann


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