Re: Re: How to make database queries that “filters” results according to tuples of values?

Remember that |= is just a shorthand for

query = query | ... rest of parameters

So in the end it is just an "or" like you say, nothing magical about that

Glad I could help

Regards!

On Thu, Nov 27, 2014 at 4:56 AM, <lnzy35en@gmx.de> wrote:

Hi Vijay,

 

thank you very much. I have not known, that |= also could be used on Q().

Thought Q is only there for making "or" "not" and so stuff of calls! Great!

 

Best Regards,

Mike

 

Gesendet: Mittwoch, 26. November 2014 um 20:30 Uhr
Von: "Vijay Khemlani" <vkhemlan@gmail.com>
An: django-users@googlegroups.com
Betreff: Re: How to make database queries that "filters" results according to tuples of values?

I think you could construct a Q object like this:

 

from django.db.models import Q

 

query = Q()

for preference in user.preferences.all():

    query |= Q(dish=preference.dish) & Q(ingredient=preference.ingredient)

 

Meal.objects.filter(query)

 

That returns the meals where their (ingredient, dish) combination match at least one of the preferences of the user.

 

On Wed, Nov 26, 2014 at 3:54 PM, <lnzy35en@gmx.de> wrote:

Hi,

let's assume I have the following model:

 

class Ingredient(models.Model):

    ingredient= models.CharField(max_length=255)

class Dish(models.Model):

    BREAKFAST = 'bf'

    LUNCH = 'l'

    DINNER = 'D'

    DISH_CHOICES = (

        (BREAKFAST, 'Breakfast'),

        (LUNCH, 'Lunch'),

        (DINNER, 'Dinner'),

    )

    dish = models.CharField(max_length=32,choices=DISH_CHOICES,unique=True)

 

class Preference(models.Model):

    ingredient= models.ForeignKey(Ingredient)

    dish = models.ForeignKey(Dish)

    date_created = models.DateTimeField(auto_now_add=True)

    date_updated = models.DateTimeField(auto_now=True, verbose_name='Date updated')

    owner  = models.ForeignKey(User, related_name='preferences')

 

class Meal(models.Model):

    name = models.CharField(max_length=255)

    ingredient= models.ManyToManyField(Ingredient)

    kalorins = models.IntegerField()

    thumbnail = models.URLField(blank=True)

    dish= models.ForeignKey(Dish)

I want to execute a database query in the view resulting all meals that would match the preference's of a user.
But something like: result = Meal.objects.filter(ingredient__in=user.request.name.pfreferences) will select all the meals witch are in the preference list of the user, regardless his choice of the "Dish Type". So if a person only likes tomatos for breakfast, he also will get all meals with tomates for lunch and dinner.

 

So I am looking for a way, which returns only the "Meals" where the ingredients and the dish BOTH match the ingredients and the dish of the user's Preference.

I haven't found anything in the django books I have or the documentation

Thanks a lot.

Best Regards,

Mike

 

 

 

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