A more complete explanation:
Ordering on the related table works fine as long as all the articles
have an associated ArticleRank (article_rank.rank, depending on how you
look at it).
> order_by = '-articlerank__rank'
> art_list = Article.objects.filter(\
> title__icontains=term, status='PUBLISHED')\
> .distance(pnt)\
> .order_by(order_by)
A search that includes articles with no entry in the ArticleRank table
*does* include them in the result set, but puts them *first* in the
ordering results. Then, it includes the rest of the correctly ordered
results. This is a little confusing.
If I try to access the article's rank (one with a missing ranking) I get
an error. So, I'm trapping the exception like this:
try:
article_rank = art.articlerank.rank
except ArticleRank.DoesNotExist:
article_rank = 0
That's okay, but the ordering is still a problem. I want it to treat
missing rank as if it were 0 and put those at the bottom of the list.
I suppose I could just add the articles with no ranking to the
article_rank table and give them a ranking of 0.
Is there a better way?
Liam
Malcolm Tredinnick wrote:
> (You forgot to include a title. I nearly nuked this as spam, by
> accident. So I've thrown in a title for fun.)
>
> On Sun, 2008-12-14 at 19:50 -0800, Info Cascade wrote:
>
>> Hi --
>>
>> I have a question about many-to-many relationships and how to reference
>> a related object field using Django syntax via the Manager class.
>> I think this is probably pretty simple and just reflects my inexperience
>> working with Django (which overall I am enjoying, btw.)
>> Anyway, the models look like this:
>>
>> class Poi(models.Model): # A "Point of Interest"
>> id = models.AutoField(primary_key=True)
>>
>
> By the way, you can leave this out. Django will automatically create a
> field with that name for you that is the primary key.
>
>
>> title = models.CharField(max_length=1024, null=False, db_index=True)
>> articles = models.ManyToManyField('Article', null=True,
>> db_table='poi_articles')
>>
>> class PoiRank(models.Model):
>> poi = models.OneToOneField(Poi, primary_key=True)
>> rank = models.IntegerField(null = False, blank = False)
>>
>> class Article(models.Model):
>> id = models.AutoField(primary_key=True)
>> title = models.CharField(max_length=1024, blank=True, db_index=True)
>> pois = models.ManyToManyField(Poi, null=True, db_table='poi_articles')
>> status = models.CharField(max_length=27, blank=True)
>>
>>
>> One Poi can have many Articles written about it. One Article can be
>> referenced by many Poi's.
>> A Poi has 0 or 1 "rank" value which is some measure of its popularity.
>>
>> Now, I had to set the db_table name to poi_articles because otherwise I
>> ended up with what were essentially duplicate tables (just with the
>> order of the foreign keys swapped).
>> Of course, doing that I then had to remove the duplicate poi_articles
>> table that got generated the first time I ran syncdb.
>> This makes me think that I may not have set things up correctly in the
>> first place.
>>
>
> I don't see anything in your explanation that requires having a
> ManyToManyField on both Article and Poi. Just put the ManyToMany on one
> of the models and you can still use it to refer back and forth. Django's
> relation fields are created nicely so that you only need to specify one
> end, not both. What you have done to hack around this sounds like it
> might lead to problems later.
>
> For argument's sake, I'll assume you get rid of the "pois" attribute on
> the Article table
>
>
>> Anyway, after doing a query I have a QuerySet of articles. I need to
>> know that the rank of the article is. That's all. It should be simple,
>> right?
>>
>
> The problem is that your requirement is not well-defined. If you have
> any particular single Article object, there can be many Poi objects
> related to it (that was part of your problem description), each one
> having a different rank. There's no single rank value associated with a
> single Article.
>
> Regards,
> Malcolm
>
>
>
> >
>
>
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