Working on a last-minute mapping app for PyCon here, I'm currently
using a raw SQL query to SELECT information from People (Model) who all
share the same Tag (Model in a ManyToMany with People). I'm feeding
the query a range of lat/lon and the tag I want,
c = db.cursor()
c.execute("""select p.id, p.name, p.lat, p.lon from maps_people as
p
left join maps_tags_person as pt on pt.person_id = p.id
left join maps_tags as t on t.id = pt.tag_id
where t.tag = '%s'
and p.lat >= %s
and p.lon >= %s
and p.lat <= %s
and p.lon <= %s
order by p.id""" % (request_tag, minlat, minlon, maxlat,
maxlon))
r = c.fetchall()
c.close()
I'd just like to figure out the Django API equivalent (if there is one)
to do something like this.
I was thinking, like, people.get_list(lat__gte=minlat, lon__gte=minlon,
lat__lte=maxlat, lon__lte=maxlon, has__tag=tag) or whatever... ideas?
---
Second question,
What is a good method of keeping a count of ManyToMany relationships
that each entry in the table has? In the example above, I added a
meta.IntegerField to the Tag Model, and I want it to hold the # of
people that have that tag. I don't want to calculate this as-needed
(way to often, if I use it)... I can't really import the model IN the
model, can I? (I tried, and then my brain exploded)
My original thought was to just add a _pre_save that updated with the
count everytime a Tag was saved (Tags aren't really edited, so pretty
much ALL saves affect the number of relationships) ... but I wasn't
sure what a "best practice" method of this was.
---
Thanks,
Brett
