django-orm

问题 The ORM in Django lets us easily annotate (add fields to) querysets based on related data, hwoever I can't find a way to get multiple annotations for different filtered subsets of related data. This is being asked in relation to django-helpdesk, an open-source Django-powered trouble-ticket tracker. I need to have data pivoted like this for charting and reporting purposes Consider these models: CHOICE_LIST = ( ('open', 'Open'), ('closed', 'Closed'), ) class Queue(models.model): name = models

问题 I have a model, which looks like: class StaffMember(models.Model): id = models.OneToOneField(to=User, unique=True, primary_key=True, related_name='staff_member') supervisor = models.ForeignKey(to='self', null=True, blank=True, related_name='team_members') My current hierarchy of team is designed in such a way that there is let's say an Admin (who is at the top most point of hierarchy). Now, let's say 3 people (A, B, C) report to Admin and each one of A, B and C have their own team reporting

问题 I'm using django-taggit, which handles the attachment of tags to arbitrary content types. I imported a large tag list, which contains many uppercase words, as well as lowercase words. Now, I' trying to get objects of another class containing a set of tags, but I want to compare case insensitively. When I do this: Media.objects.filter(tags__name__in=['tag1', 'tag2']) objects containing e.g. the tag "Tag1" are not found, only those ones with "tag1" or "tag2". Is there any possibility in the

问题 I read that InnoDB automatically creates indexes for Foreign-key. Does MySQL Workbench automatically create indexes for foreign keys? Does MySQL index foreign key columns automatically? https://dev.mysql.com/doc/refman/5.6/en/innodb-foreign-key-constraints.html But some of my foreign keys do not have the index in the table. Check pharmaceutical_id foreign-key field. It does not have an index. | pharmaceuticals_pharmaceuticalcode | CREATE TABLE `pharmaceuticals_pharmaceuticalcode` ( `id` int

问题 The following shows the distinct count is 2247 In [6]: VirtualMachineResources.objects.all().values('machine', 'cluster') ...: .distinct().count() Out[6]: 2247 But then when I loop through it, it returned way more than it should: In [4]: a = [] ...: for resource in VirtualMachineResources.objects.all().values('mach ...: ine', 'cluster').distinct(): ...: if resource['cluster']: ...: a.append(resource['cluster']) ...: ...: In [5]: len(a) Out[5]: 96953 Given the records have cluster field being

问题 I'm trying to construct a moderately complex filter in the Django ORM, and I'm not sure if I could do it more efficiently. My app lets users search for shoes in a particular size. So if they select a size (or multiple sizes), I look for all the shoes available in that size. This is my model structure. There's an object for each shoe ( Shoe ), an object for each size ( ShoeSize ) (standardised across manufacturers), and an object ( ShoeSizeAvailable ) that only gets created if a particular

问题 In Django, on a given model it looks like the RelatedManager may only be set statically (see: docs) but is there any way to set the order_by on the related manager for a given Queryset? I tried using prefetch_related and Prefetch , but that does not seem to work: qs = qs.prefetch_related( Prefetch('item_set', queryset=Item.objects.order_by('capture_dt').all())) res = qs.first().item_set.all().ordered In this case res is False . The problem comes when I try to access the related manager:

问题 I'm doing a migration changing a nullable field to be not-nullable. The new __init__ routine ensures that fields can't be null by doing some custom callisthenics to come up with a suitable default. The question is whether it is essential to migrate the existing data to apply the new rules for a default, or will those rules be applied automagically whenever a legacy object is retrieved? Reading the source I suspect the ORM restores a pickle of the saved data, thus I would need to update all

问题 I've read everything I can find on ManyToMany relationships in Django, but so far I'm not seeing anything that solves my specific problem of having a ManyToMany-Through relationship alongside a simple ManyToMany that Django handles so effortlessly on its own. Consider these models: class Treatment(models.Model): ... book = models.ManyToManyField(Book, through='TreatmentLocation') category = models.ManyToManyField(Category) class Book(models.Model): name = models.CharField(...) class

问题 I've decided to use Django 1.7 for the first time with Python 3. I need to be able to work with legacy latin1 database which contains utf8 data. I know it sucks, but the database is so huge that it's really impossible to change this. So I tried following: DATABASES = { 'ENGINE' : 'django.db.backends.mysql', // using MySQL-python fork with support for py3 ... 'OPTIONS' : { 'init_command': "SET character_set_results = 'latin1'", #'read_default_file': '/etc/my.cnf.d/client.cnf', // I've also