Re: Complex queries with datetime field

[Stefan Tunsch]

Well, first of all I can't believe I've overlooked the __in field lookup... I wasn't aware of it's existance. Sorry. Regarding the __year, __month and __day lookups I'm using in my code: I do it because I want to filter all datetime objects of a specific day. I want to filter all datetime objects like datetime.datetime(2009, 1, 29, 12, 33, 41, 234000) that are in a day like datetime.date(2009, 1, 29). I would want to do something like mydatetimefield__date=datetime.date(2009, 1, 29) but since that option does not exist, I am doing this strange thing with year, month and day. I could also simply split my datetime field into two fields. A date field and a time field. This way I would be able to filter out objects that are in a list of dates, with the __in lookup and things would work very smoothly. Regarding the Q objects, the problem strives of wanting to create the Q object dynamically. The way I've been trying to do this is with a dict expansion as Tim Chase pointed out in this post: http://groups.google.es/group/django-users/browse_thread/thread/325752f0a113b5ef/ed1a2fc7eb6e6e54?hl=es#ed1a2fc7eb6e6e54 The problem with this approach is that I seem only to be able to add simple Q objects one by one. In the same post Sebastian Bauer points out a different approach which actually works well in my scenario here. The following code does it's job as it should: qdates = None for myfinaldate in date_list:     if qdates:                 qdates= qdates | (Q(mydatetimefield__day=myfinaldate.day) & Q(mydatetimefield__month=myfinaldatemonth) & Q(mydatetimefield__year=myfinaldate.year))             else:                 qfechas = Q(mydatetimefield__day=myfinaldate.day) & Q(mydatetimefield__month=myfinaldate.month) & Q(mydatetimefield__year=myfinaldate.year) myqueryset = myqueryset.filter(qdates) Regards, Stefan Malcolm Tredinnick escribió: On Wed, 2009-01-28 at 16:10 +0100, Stefan Tunsch wrote: Hi! I have a calendar that permits multiple selections of dates. My view has to filter the data depending on the selected dates. I am unsure about how I can construct a query that filters correctly the data. I construct my list of datetime objects like this: list = request.session['selected_dates'].split(',') date_list = [datetime.datetime(int(mydate.split('/')[2]), int(mydate.split('/')[0]), int(mydate.split('/')[1])) for mydate in list] If I only have one date in my list, this works: qdates = Q(mydatetimefield__year=date_list[0].year, mydatetimefield__month=date_list[0].month, mydatetimefield__day=date_list[0].day) An easier approach than this is to convert the input values to a Python datetime object and then filter using Q(mydatetimefield=input_datetime) The "__year", "__month" and "__day" lookups are forcing the database to make three comparisons on the same field, instead of one. It's also a lot less readable at the Python level. myqueryset = myqueryset.filter(qdates) #I am modifying an existing queryset The problem stems of the need to assign new values to my Q object dynamically. I have tried this, but it does not work. (It will always filter only to the first selected date): qdates = Q() for myfinaldate in date_list: qdates |= Q(**{"mydatetimefield__year": myfinaldateyear}) qdates &= Q(**{"mydatetimefield__month": myfinaldate.month}) qdates &= Q(**{"mydatetimefield__day": myfinaldate.day}) First I would want to know if there is a better way to lookup data that is IN a range of data? Since you're not using "IN" here at all, this doesn't seem to relate to the code you're doing. I have been wondering why you're not using the "__in" lookup type here. If you have a list of Python datetime objects (and not doing that is just doing things the hard way), then Q(mydatetimefield__in = [...]) if the easiest way to do this. Construct the list of datetimes objects before constructing the filter. Second I would want to know if I can somehow add to my Q object a mix of groups of ANDed values that are ORed between them? Yes. But you have to add them as parenthesised groups. Your above code seems to be making some kind of assumptions about the precedence of "|" and "&" and I can't work out what it's doing. However, the straightforward (Q(..) | Q(...)) & (Q(...) | Q(...) | Q(...)) sort of style works. You could construct the pieces (the "|" bits in the above example) and then "&" them together at the end, for example. Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---