I wanted to order a query set on the basis of a time of a datetime field.
I have used the following (here Tasks is my model and datetime is the field)
Tasks.objects.all().order_by('datetime.time')
this doesn't work and also
Tasks.objects.all().order_by('datetime__time')
doesn't work as it is part of the same model.
I tried using .annotate() but I don't know how exactly to do it.
How should I go about doing this?
Tasks.objects.all().order_by('datetime__hour')
or
Tasks.objects.all().order_by('datetime__minute')
Task.objects.all().order_by('datetime__hour', 'datetime__minute')
Related
I am having this problem with prostgresql and django:
I have a lot of events that were created on a certain date at a certain time which is stored in a datetime field created .
I want to have aggregations based on the date part of the created field. The simplest examples is: how many event are in each day of this month?.
The created field is timezone aware. So the result should change depending on the timezone the user is in. For example if you created 2 events at 23:30 UTC time on 2017-10-02 if you view them from UTC-1 you should see them on 3rd of October at 00:30 and the totals should add for the 3rd.
I am struggling to find a solution to this problem that works with a lot of data. So doing for each day and SQL statement is not an option. I want something that translates into:
SELECT count(*) from table GROUP BY date
Now I found a solution for the first part of the problem:
from django.db import connection
truncate_date = connection.ops.date_trunc_sql('day', 'created')
queryset = queryset.extra({'day': truncate_date})
total_list = list(queryset.values('day').annotate(amount=Count('id')).order_by('day'))
Is there a way to add to this the timezone that should be used by the date_trunc_sql function to calculate the day? Or some other function before date_trunc_sql and then chain that one.
Thanks!
You're probably looking for this: timezone aware date_trunc function
However bear in mind this might conflict with how your django is configured. https://docs.djangoproject.com/en/1.11/topics/i18n/timezones/
Django 2.2+ supports the TruncDate database function with timezones
You can now do the following to :
import pytz
east_coast = pytz.timezone('America/New_York')
queryset.annotate(created_date=TruncDay("created", tzinfo=east_coast))
.values("created_date")
.order_by("created_date")
.annotate(count=Count("created_date"))
.order_by("-created_date")
I have a field which will represent the start time of an event and I am using the Django DateTimeField for this.
This field is mandatory but sometimes the users will only know the start date and not the time.
Is there anyway to make the time part optional and keep the date part mandatory?
Maybe you should try to separate date from time. There are DateField and TimeField for that.
Example for use at the views or models:
You can use function strptime to show the datetime field any formats.
from datetime import datetime
datetime.now().strftime('%Y-%m-%d')
# print string '2013-06-25'
Example for use at the templates:
you can use templatetag date
{{ datetime_field|date:"Y-m-d" }}
I have used this query in my view..
temp2=transaction.objects.filter(user_id=client_obj,Date_of_trans.date()=rec_var1)[0].Trans_Amount
I need to compare a datetime field present in my model named Date_of_trans to a variable received from user but the code is not working... what query should be written?
This is basically a sql query. So you should think like that. How can you do this in sql. I mean what condition will you apply in sql. For finding records of particular date with datetime field you should check records between start of the day to end of the day.
try this
from datetime import datetime, time
temp2=transaction.objects.filter(user_id=client_obj,Date_of_trans>datetime.combine(rec_var1, time(0,0,0)), Date_of_trans <= datetime.combine(rec_var1, time(23,59,59)) )[0].Trans_Amount
The above code is written taking into consideration that rec_var1 is a date() object.
Here you check all transactions between start of the day, till end of the day. I think this will resolve your problem.
I've use datetime.combine function which combines date and time object to form datetime object which is required here.
Thanks
I've got an app where users create pages. I want to run a simple DB query that returns how many users have created more than 2 pages.
This is essentially what I want to do, but of course it's not the right method:
User.objects.select_related('page__gte=2').count()
What am I missing?
You should use aggregates.
from django.db.models import Count
User.objects.annotate(page_count=Count('page')).filter(page_count__gte=2).count()
In my case, I didn't use last .count() like the other answer and it also works nice.
from django.db.models import Count
User.objects.annotate( our_param=Count("all_comments")).filter(our_param__gt=12)
use aggregate() function with django.db.models methods!
this is so useful and not really crushing with other annotation aggregated columns.
*use aggregate() at the last step of calculation, it turns your queryset to dict.
below is my code snippet using them.
cnt = q.values("person__year_of_birth").filter(person__year_of_birth__lte=year_interval_10)\
.filter(person__year_of_birth__gt=year_interval_10-10)\
.annotate(group_cnt=Count("visit_occurrence_id")).aggregate(Sum("group_cnt"))
I have a Django model with a created timestamp and I'd like to get the counts of objects created on each day. I was hoping to use the aggregation functionality in Django but I can't figure out how to solve my problem with it. Assuming that doesn't work I can always fall back to just getting all of the dates with values_list but I'd prefer to give the work to Django or the DB. How would you do it?
Alex pointed to the right answer in the comment:
Count number of records by date in Django
Credit goes to ara818
Guidoism.objects.extra({'created':"date(created)"}).values('created').annotate(created_count=Count('id'))
from django.db.models import Count
Guidoism.objects \
# get specific dates (not hours for example) and store in "created"
.extra({'created':"date(created)"})
# get a values list of only "created" defined earlier
.values('created')
# annotate each day by Count of Guidoism objects
.annotate(created_count=Count('id'))
I learn new tricks every day reading stack.. awesome!
Use the count method:
YourModel.objects.filter(published_on=datetime.date(2011, 4, 1)).count()