P.S. id == 6 disappears in ascending and id == 3 disappears in
descending.
It's not a surprise that id == 5 is duplicated because it is the only
Listing__book which has a relationship with two courses, the rest have
a relationship with only one. That part does look suspicious to me
though, as if the duplicate id "swallowing up" the missing records. I
have no clue why though... hope these details help clarify my problem.
On Nov 26, 1:31 pm, David <davidkazuh...@gmail.com> wrote:
> When I order over a ManyToMany relationship, certain records will not
> appear. The record which disappears changes depending on the order by
> which I sort it. Specifically:
>
> >>> Listing.objects.order_by("book__courses")
>
> gives me Listings with id's (5, 1, 3, 5, 2, 4), and
>
> >>> Listing.objects.order_by("-book__courses")
>
> gives me Listings with id's (6, 4, 5, 2, 5,1)
>
> There is nothing wrong with the ordering. The problem is that a record
> is disappearing in the ordering process. My pertinent models are
> below. Any clues?
>
> -------------------------------------------------------
> class Course(models.Model):
> """
> Basic course data
> """
> division = models.CharField(max_length=5)
> number = models.CharField(max_length=4)
> title = models.CharField(max_length=250)
>
> class Meta:
> ordering = ('division', 'number')
>
> def code(self):
> return "%s %s" % (self.division, self.number)
>
> def __unicode__(self):
> return self.code()
>
> class Book(models.Model):
> """
> Information on a book (as opposed to a particular copy of it)
> The attributes should be self-explanatory
> """
> title = models.CharField(max_length=250)
> author = models.CharField(max_length=70)
> barcode = models.CharField(max_length=50)
> edition = models.PositiveSmallIntegerField()
> courses = models.ManyToManyField(Course)
>
> def __unicode__(self):
> return self.title
>
> def course_codes(self):
> """
> returns a list of courses in the form
> course1, course2, course3
> """
> course_list = ""
> for course in self.courses.all():
> course_list += "%s, " % course.code()
> # [:-2] takes off the trailing comma and space
> return course_list[:-2]
> def title_list(self):
> return self.author
>
> class Listing(models.Model):
> """
> For when a student lists a particular copy of a book.
> Keeps track of
> * when and who listed (is selling) it
> * if and who is currently holding it
> * when it was last put on hold
> * when it finally got sold
> * whether the listing is flagged for deletion or not
> """
> STATUS_CHOICES = (
> (u'F', u'For Sale'),
> (u'M', u'Missing'),
> (u'O', u'On Hold'),
> (u'P', u'Seller Paid'),
> (u'S', u'Sold'),
> (u'T', u'To Be Deleted'),
> (u'D', u'Deleted'),
> )
>
> book = models.ForeignKey(Book)
> list_date = models.DateTimeField('Date Listed', auto_now_add=True)
> seller = models.ForeignKey(User, related_name="selling")
> sell_date = models.DateTimeField('Date Sold', blank=True,
> null=True)
> holder = models.ForeignKey(User, related_name="holding",
> blank=True, null=True)
> hold_date = models.DateTimeField('Date Held', blank=True,
> null=True)
> price = models.DecimalField(max_digits=7, decimal_places=2)
> status = models.CharField(max_length=1, choices=STATUS_CHOICES)
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