Re: Best way to use a 'all' QuerySet as a dict with id first

Thanks for the answer, I just wondered if there was a built-in solution in
Django.

On 27/09/14 06:01, tkdchen wrote:
>
>
> On Saturday, September 27, 2014 9:06:58 PM UTC+8, aRkadeFR wrote:
> >
> > @James Brewer:
> > If I change my code, I can have this user_ids list.
> > btw, it's filter and not get if you're searching multiple objects (the
> > user_ids).
> >
> > @Alejandro Varas G.:
> > That doesn't change the fact that 'User.objects.get(id=X)' will hit the
> > database everytime.
> >
> > Right now, the problem is solved, by creating the AllUserSet, but I think
> > my
> > code is pretty ugly, and it seems strange to me that the ORM can't handle
> > that
> > built-in, by caching the .all() or .filter(id__in=users_ids)
> >
> >
> Django actually caches all objects fetched when it evaluates .all or
> .filter method. The problem you are facing is that how to reuse the cached
> objects efficiently to avoid hitting database with unnecessary SQL queries.
> James gave you a good solution. Based on his solution, you don't need to
> call the `get' method each time getting user by id. Just iterate users
> object and find the right one by comparing id.
>
>
>
>
> > The ideally solution would be something like:
> >
> > AllUser = User.objects.all()
> >
> > for i in user_id:
> > AllUser.get(id=i)
> >
> >
> This piece of code would be changed to
>
> AllUser = User.objects.all()
> for i in user_id:
> for user in AllUser:
> if user.pk == i:
> print 'find the user'
>
> or, even you may construct AllUser to dict to simplify the search
>
> AllUser = dict((user.pk, user) for user in User.objects.all()) # Here, hit
> db, only once
> for i in user_id:
> user = AllUser.get(i, None) # search by id in memory
> if user is not None:
> print 'find the user'
>
> Hope, this could help you.
>
> But this code hits the database every time the 'get' is called.
> >
> >
> > On 26/09/14 12:36, James Brewer wrote:
> > > Do you have a single list of the IDs you want? If so, you can do
> > something
> > > like `User.objects.get(id__in=user_ids)`. This will fetch all Users
> > whose
> > > `id` is in some list `user_ids`.
> > >
> > > Does that help?
> > >
> > > Happy hacking!
> > >
> > > James
> > >
> > > On Fri, Sep 26, 2014 at 11:43 AM, Alejandro Varas G. <alej0...@gmail.com
> > <javascript:>>
> > > wrote:
> > >
> > > > Hi,
> > > >
> > > > You should use User.objects.get(id=X)
> > > >
> > > > Best
> > > > El 26/09/2014 15:28, "aRkadeFR" <con...@arkade.info <javascript:>>
> > escribió:
> > > >
> > > > >
> > > > > Hey!
> > > > >
> > > > > I'm having a hard time trying to reduce the number of SQL queries on
> > a
> > > > view.
> > > > >
> > > > > Basically, I'm fetching all my User, with User.objects.all(), and
> > save
> > > > this
> > > > > queryset as AllUser.
> > > > >
> > > > > Then every time I need to get the user with the id = X , I'm calling
> > a
> > > > function
> > > > > 'get_user_from_id', that iterate over the AllUser queryset variable,
> > and
> > > > when
> > > > > it finds the id, returns it.
> > > > >
> > > > > I considerably reduced the number of SQL queries, but I would like
> > to
> > > > know if
> > > > > you think of a better way?
> > > > >
> > > > > Thank you
> > > > >
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> > > > <
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> > >
> > >
> > > --
> > > James Brewer
> > > jamesbrewer.io
> > >
> > > --
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