Hi all,
Here is a raw pull request, allowing lookup instances passing to filter
method
There are two new test cases working:
1. Passing lookup with F object:
Article.objects.filter(GreaterThan(F('id'), Value(5)))
2. And passing lookup with transforms:
Article.objects.filter(Contains(Upper(Lower(Upper(F('headline')))),
'ARTICLE 5'))
All the existing tests are passing successfully, by the way (at least for
SQLite backend).
Several comments:
- F expressions became real expressions (Expression subclass).
- Expression got a new method - get_source_f_object, which walks through
children classes and find if it has F object passed. In that case
output_field-related code should be postponed, until compiler resolves it
(which cannot be done during lookup init time).
- some code related to query.build_filter method (responsible to
lookups/transform parsing, and calculating joins), extracted into separate
helper classes - QueryKeywordLookupHelper and QueryObjectLookupHelper. They
have common code base, but some of methods work in a different way.
Except review, it would be really great if someone help with writing test
cases (and I'll get them working in case of any issues). Also, there is a
workaround field=None -> isnull=True for oracle database, can anybody check
if it is working correctly?
Regards,
Alexey
On Thursday, October 1, 2015 at 11:38:39 AM UTC+3, Anssi Kääriäinen wrote:
>
> Lets concentrate on making expressions in filter calls and lookups as
> expressions reality. When we have done that we can try out different
> syntax approaches in 3rd party apps. Finally, after we have field
> tested the approaches, we can merge something in to Django.
>
> - Anssi
>
> On Thu, Oct 1, 2015 at 10:49 AM, Alexey Zankevich
> <alex.za...@gmail.com <javascript:>> wrote:
> >> I think the `F('name').decode('utf-8')` syntax is a good candidate for
> >> core.
> >
> > When Django supports expression lookups, it will be possible to build
> syntax
> > sugar third-party library on top of it.
> > For example, it will be possible to implement dotted syntax for F
> objects:
> >
> > UserModel.objects.filter(Decode(F.user.name, 'utf-8') == u'Бармаглот')
> >
> > alternatively it can be even combined with your syntax
> >
> > UserModel.objects.filter(F.user.name.decode('utf-8') == u'Бармаглот')
> >
> > However, the second solution will be more complicated from technical
> point
> > of view (as will require lazy object, collecting all the func or
> transform
> > calls), also it will require to be really careful with transform names
> not
> > to conflict with possible field names.
> > For example, it's hardly possible to have "decode" field in the model,
> but
> > easily - "date".
> >
> >
> > On Thursday, October 1, 2015 at 10:18:40 AM UTC+3, Loïc Bistuer wrote:
> >>
> >> > On Oct 1, 2015, at 13:38, Anssi Kääriäinen <akaa...@gmail.com>
> wrote:
> >> >
> >> > +1 to not requiring all transforms to handle __underscore__ syntax.
> >>
> >> +1
> >>
> >> > I think what we want to do is allow users choose which syntax they
> >> > prefer. The idea is that Django will support both JSONExtract('data',
> >> > path=['owner', 'other_pets', 0, 'name']) and
> >> > data__owner__other_pets__0__name out of the box.
> >> >
> >> > We will also make it possible to support callable transforms. For
> >> > example:
> >> > filter(Exact(Decode(F('name'), 'utf-8'), Value(u'Бармаглот')))
> >> > is equivalent to
> >> > filter(F('name').decode('utf-8') == Value(u'Бармаглот'))
> >> >
> >> > The callable transforms syntax will not be a part of Django, but it
> >> > will be possible to create an extension for this (it is actually
> >> > surprisingly easy to do once we have support for expressions in
> >> > filter).
> >>
> >> I'm pretty convinced we need a better API / sugar as part of core in
> the
> >> long run.
> >>
> >> The `filter(Exact(Decode(F('name'), 'utf-8'), Value(u'Бармаглот')))`
> >> syntax is not pythonic and very hard to decipher, and we've reached the
> >> limits of our historical double underscore syntax (doesn't support
> multiple
> >> arguments, limited to ascii, etc.).
> >>
> >> I think the `F('name').decode('utf-8')` syntax is a good candidate for
> >> core:
> >>
> >> - It's a small extension to the existing F objects, so it's easy to
> grasp
> >> for existing Django users.
> >> - It's just a thin sugar on top of the canonical API.
> >> - All the required machinery being already in place (lookup & transform
> >> registration) the change to Django is minimal.
> >>
> >> > - Anssi
> >> >
> >> > On Thu, Oct 1, 2015 at 4:00 AM, Josh Smeaton <josh.s...@gmail.com>
> >> > wrote:
> >> >> No, not all Lookups or Transforms are required to handle
> __underscore__
> >> >> syntax. The entire point of supporting object based lookups is to
> >> >> handle
> >> >> cases that get more complex than a single argument transform or a
> left
> >> >> and
> >> >> right hand side lookup.
> >> >>
> >> >> In particular, I think your Decode(utf8) example is a good one. It
> >> >> shows
> >> >> that you could maybe shoehorn multiple arg transforms into the
> >> >> __underscore__ api, but it wouldn't be entirely obvious how to do
> so.
> >> >> You'd
> >> >> probably need to register partial transformations for each encoding
> you
> >> >> wanted to support. The contrib.postgres module has (from memory)
> >> >> KeyTransform classes that do a similar thing.
> >> >>
> >> >> Cheers
> >> >>
> >> >>
> >> >> On Thursday, 1 October 2015 02:13:41 UTC+10, Alexey Zankevich wrote:
> >> >>>
> >> >>> I'll try to turn lookups into expression (will use master branch).
> >> >>> I also have a question. Meanwhile the old query syntax with
> >> >>> underscores is
> >> >>> pretty good for simple queries (like
> Model.objects.filter(name='Bob'),
> >> >>> it
> >> >>> gets really ugly for parametrized calls, a new JSONField is a good
> >> >>> example
> >> >>> of that:
> >> >>>
> >> >>>>>> Dog.objects.filter(data__owner__other_pets__0__name='Fishy')
> >> >>> [<Dog: Rufus>]
> >> >>>
> >> >>> It will get even more messy if we want to pass a string as a second
> >> >>> param
> >> >>> of the func.
> >> >>>
> >> >>> ex.:
> >> >>>
> >> >>> 1. filter(Decode(F('name'), 'utf-8'), Value(u'Бармаглот')) # <-
> neat
> >> >>> 2. filter(name__decode__utf8=u'Бармаглот') # <- ?? ambiguous and
> not
> >> >>> nice
> >> >>> at all
> >> >>>
> >> >>> So question - is it implied all the funcs, transforms and lookups
> to
> >> >>> have
> >> >>> underscore-based equivalent? It can affect the final implementation
> >> >>> pretty
> >> >>> much. In my opinion underscore-based equivalent should not be
> really
> >> >>> required for funcs (the problem doesn't seem to affect transforms
> as
> >> >>> they
> >> >>> will not accept multiple params according to another thread).
> >> >>>
> >> >>> Thanks,
> >> >>> Alexey
> >> >>>
> >> >>>
> >> >>> On Wednesday, September 30, 2015 at 9:19:51 AM UTC+3, Anssi
> Kääriäinen
> >> >>> wrote:
> >> >>>>
> >> >>>> I don't think we need split-to-subq support for Lookups before we
> >> >>>> make
> >> >>>> them expressions. Lookups as expressions are usable outside
> >> >>>> .filter(),
> >> >>>> and we need the split-to-subq support only in .filter(expression).
> >> >>>>
> >> >>>> - Anssi
> >> >>>>
> >> >>>> On Wed, Sep 30, 2015 at 8:46 AM, Josh Smeaton <josh.s...@gmail.com>
>
> >> >>>> wrote:
> >> >>>>> I'm mixing my versions, sorry to those following along. 1.9 has
> just
> >> >>>>> reached
> >> >>>>> alpha. Lookups as Expressions should be doable for 1.10 which
> master
> >> >>>>> is
> >> >>>>> currently tracking.
> >> >>>>>
> >> >>>>> Cheers
> >> >>>>>
> >> >>>>>
> >> >>>>> On Wednesday, 30 September 2015 15:31:24 UTC+10, Josh Smeaton
> wrote:
> >> >>>>>>
> >> >>>>>> The alpha for 1.10 has already been cut, and I'm not sure that
> the
> >> >>>>>> kinds
> >> >>>>>> of changes needed here are appropriate to add now that the alpha
> is
> >> >>>>>> out. One
> >> >>>>>> could *maybe* make the argument that changing Lookup to an
> >> >>>>>> Expression
> >> >>>>>> now
> >> >>>>>> rather than later is the right move considering Transforms just
> >> >>>>>> underwent
> >> >>>>>> the same change for 1.10. Personally though, I don't think I
> have
> >> >>>>>> the
> >> >>>>>> time
> >> >>>>>> right now to do this change. I would support you if you were
> able,
> >> >>>>>> but
> >> >>>>>> we'd
> >> >>>>>> still be at the mercy of the technical board (I assume) for
> getting
> >> >>>>>> this
> >> >>>>>> change in for 1.10.
> >> >>>>>>
> >> >>>>>> Do you think Lookup as Expressions requires the subquery/exclude
> >> >>>>>> fix
> >> >>>>>> you
> >> >>>>>> mention above? I would think not -- not until we were ready to
> >> >>>>>> document and
> >> >>>>>> support .filter(Lookup(F(), Value()). If it wasn't a
> requirement,
> >> >>>>>> it'd
> >> >>>>>> make
> >> >>>>>> the Lookup->Expression work much easier. It wouldn't even need
> to
> >> >>>>>> be
> >> >>>>>> documented (other than the release notes), as it'd just be an
> >> >>>>>> implementation
> >> >>>>>> change.
> >> >>>>>>
> >> >>>>>> Cheers,
> >> >>>>>>
> >> >>>>>> On Wednesday, 30 September 2015 14:33:14 UTC+10, Anssi
> Kääriäinen
> >> >>>>>> wrote:
> >> >>>>>>>
> >> >>>>>>> On the core ORM side we need to make
> >> >>>>>>> .exclude(LessThan(F('friends__age'), 30)) do a subquery. This
> way
> >> >>>>>>> .exclude(friends__age__lt=30) does the same thing as the
> >> >>>>>>> expression
> >> >>>>>>> version. This isn't that easy to do. If we just use
> >> >>>>>>> resolve_expression, then the friends relation will generate a
> >> >>>>>>> join,
> >> >>>>>>> and then as second step do a negated filter on the joined
> value.
> >> >>>>>>> Instead we want to detect that the LessThan expression needs to
> be
> >> >>>>>>> pushed in to a subquery.
> >> >>>>>>>
> >> >>>>>>> So, we need to solve:
> >> >>>>>>>
> >> >>>>>>> A) A way to ask an expression if it is referencing a multijoin
> >> >>>>>>> (possible approach is to just have a method
> >> >>>>>>> "refs_multi_valued_relation(query)")
> >> >>>>>>> B) When the ORM sees an expression that is reffing a multijoin
> in
> >> >>>>>>> an
> >> >>>>>>> exclude filter, then we need to push the expression in to a
> >> >>>>>>> subquery.
> >> >>>>>>>
> >> >>>>>>> A) requires some new work. This shouldn't be that hard to
> >> >>>>>>> implement,
> >> >>>>>>> we just recursively ask subexpressions if they reference a
> >> >>>>>>> multijoin.
> >> >>>>>>>
> >> >>>>>>> Something like https://github.com/django/django/pull/4385 will
> >> >>>>>>> make
> >> >>>>>>> B)
> >> >>>>>>> much easier to implement.
> >> >>>>>>>
> >> >>>>>>> I've been working on making Q-objects responsible for resolving
> >> >>>>>>> themselves. See https://github.com/django/django/pull/4801.
> This
> >> >>>>>>> should solve 3).
> >> >>>>>>>
> >> >>>>>>> We don't seem to be missing any major parts. I (or some
> volunteer)
> >> >>>>>>> just need to finish the PRs, and then we should be really close
> to
> >> >>>>>>> full support for expressions in filter.
> >> >>>>>>>
> >> >>>>>>> Josh: do you think we could get Lookup as expressions in to
> 1.10
> >> >>>>>>> instead of 1.11?
> >> >>>>>>>
> >> >>>>>>> - Anssi
> >> >>>>>>>
> >> >>>>>>> On Wed, Sep 30, 2015 at 3:46 AM, Josh Smeaton
> >> >>>>>>> <josh.s...@gmail.com>
> >> >>>>>>> wrote:
> >> >>>>>>>> 1. Lookups should become Expressions, just as Transforms have
> >> >>>>>>>> become
> >> >>>>>>>> Expressions. This will let us process Lookup arguments as
> >> >>>>>>>> Expressions
> >> >>>>>>>> all
> >> >>>>>>>> the way the way through. I think this should be a major goal
> for
> >> >>>>>>>> version
> >> >>>>>>>> 1.11.
> >> >>>>>>>>
> >> >>>>>>>> 2. Chaining transforms is now possible since they are just
> Func
> >> >>>>>>>> expressions.
> >> >>>>>>>> Func(Func(Func('field_name'))) is no issue.
> >> >>>>>>>>
> >> >>>>>>>> 3. Sounds like an OK idea, but I haven't looked into the
> details
> >> >>>>>>>> enough
> >> >>>>>>>> to
> >> >>>>>>>> really comment. I do think we should create the correct form
> as
> >> >>>>>>>> early
> >> >>>>>>>> as
> >> >>>>>>>> possible (parsing into a chain of Lookup/Transform
> expressions)
> >> >>>>>>>> so
> >> >>>>>>>> we
> >> >>>>>>>> don't
> >> >>>>>>>> have to do parsing in multiple places. The entry points to
> >> >>>>>>>> .filter()
> >> >>>>>>>> and
> >> >>>>>>>> .exclude(), or their direct counterparts in sql.query sound
> >> >>>>>>>> ideal.
> >> >>>>>>>> Anssi has
> >> >>>>>>>> mentioned elsewhere that WhereNode's should only contain fully
> >> >>>>>>>> resolved
> >> >>>>>>>> expressions, so resolving will need to be done directly after
> >> >>>>>>>> parsing
> >> >>>>>>>> (or
> >> >>>>>>>> during).
> >> >>>>>>>>
> >> >>>>>>>> Part 1 above can be started now if you have the time or
> interest.
> >> >>>>>>>> We
> >> >>>>>>>> can
> >> >>>>>>>> nail down the particulars of part 3 while we're solving part
> 1.
> >> >>>>>>>> Part 1
> >> >>>>>>>> may
> >> >>>>>>>> drive some of part 3.
> >> >>>>>>>>
> >> >>>>>>>> Cheers
> >> >>>>>>>>
> >> >>>>>>>>
> >> >>>>>>>> On Wednesday, 30 September 2015 04:49:54 UTC+10, Alexey
> Zankevich
> >> >>>>>>>> wrote:
> >> >>>>>>>>>
> >> >>>>>>>>> Here is a list of issues to solve to support explicit
> transforms
> >> >>>>>>>>> and
> >> >>>>>>>>> lookups by filter (and exclude) methods.
> >> >>>>>>>>>
> >> >>>>>>>>> 1. Make Lookup.__init__ signature to support initialization
> with
> >> >>>>>>>>> F
> >> >>>>>>>>> objects
> >> >>>>>>>>> or string path (e.g. GreaterThan(F('user__id'), 10) or
> >> >>>>>>>>> GreaterThan('user__id', 10)), not sure it's possible to use
> >> >>>>>>>>> simultaneously
> >> >>>>>>>>> with the current approach with lhs, rhs initialization (even
> >> >>>>>>>>> with
> >> >>>>>>>>> moving it
> >> >>>>>>>>> to a separate class method, e.g Lookup.build(lhs, rhs)), so I
> >> >>>>>>>>> assume
> >> >>>>>>>>> creating so-called util classes which will delegate
> SQL-related
> >> >>>>>>>>> functionality to existing Lookup classes.
> >> >>>>>>>>>
> >> >>>>>>>>> 2. Chain transforms by passing them as argument:
> >> >>>>>>>>>
> >> >>>>>>>>> Lower(Unaccent(F('user__name)))
> >> >>>>>>>>>
> >> >>>>>>>>> 3. Decide if Q objects shall support explicit
> lookups/transforms
> >> >>>>>>>>> as
> >> >>>>>>>>> argument as well - it's a kind of logical step, as without Q
> >> >>>>>>>>> objects
> >> >>>>>>>>> it will
> >> >>>>>>>>> not be possible to perform complicated conditions (AND, OR,
> >> >>>>>>>>> NOT).
> >> >>>>>>>>> In that case lookup/transform parsing should be moved from
> >> >>>>>>>>> QuerySet
> >> >>>>>>>>> object
> >> >>>>>>>>> to Q object - filter will take already parsed lookup tree.
> >> >>>>>>>>> Example:
> >> >>>>>>>>>
> >> >>>>>>>>> Q(user__name__lower__unaccent__icontains='Bob') will
> internally
> >> >>>>>>>>> parse
> >> >>>>>>>>> it
> >> >>>>>>>>> and build next structure:
> >> >>>>>>>>>
> >> >>>>>>>>> Q(Icontains(Lower(Unaccent(F('user__name')))), 'Bob')
> >> >>>>>>>>>
> >> >>>>>>>>>
> >> >>>>>>>>> On Sunday, August 16, 2015 at 4:18:26 PM UTC+3, Alexey
> Zankevich
> >> >>>>>>>>> wrote:
> >> >>>>>>>>>>
> >> >>>>>>>>>> Hi all,
> >> >>>>>>>>>>
> >> >>>>>>>>>> This topic is related to the current ORM query syntax with
> >> >>>>>>>>>> underscores.
> >> >>>>>>>>>> There are lots of arguing related to it, anyway it has pros
> and
> >> >>>>>>>>>> cons.
> >> >>>>>>>>>>
> >> >>>>>>>>>> Let's take a concrete example of querying a model:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> GameSession.objects.filter(user__profile__last_login_date__gte=yesterday)
> >> >>>>>>>>>>
> >> >>>>>>>>>>
> >> >>>>>>>>>> Pros:
> >> >>>>>>>>>>
> >> >>>>>>>>>> 1. The syntax is easy to understand
> >> >>>>>>>>>> 2. Can be extended with custom transforms and lookups
> >> >>>>>>>>>>
> >> >>>>>>>>>> However, there are several cons:
> >> >>>>>>>>>>
> >> >>>>>>>>>> 1. Long strings is hard to read, especially if we have
> fields
> >> >>>>>>>>>> with
> >> >>>>>>>>>> underscores.
> >> >>>>>>>>>> It's really easy to make a mistake by missing one:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> GameSession.objects.filter(user_profile__last_login_date__gte=yesterday)
> >> >>>>>>>>>>
> >> >>>>>>>>>> Not easy to catch missing underscore between user and
> profile,
> >> >>>>>>>>>> is
> >> >>>>>>>>>> it?
> >> >>>>>>>>>> Even
> >> >>>>>>>>>> though, it's not easy to say whether it should be
> >> >>>>>>>>>> "user_profile"
> >> >>>>>>>>>> attribute or
> >> >>>>>>>>>> user.profile foreign key.
> >> >>>>>>>>>>
> >> >>>>>>>>>> 2. Query strings can't be reused, thus the approach violates
> >> >>>>>>>>>> DRY
> >> >>>>>>>>>> principle.
> >> >>>>>>>>>> For example, we need to order results by last_login_date:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> GameSession.objects.filter(user__profile__last_login_date__gte=yesterday) \
> >> >>>>>>>>>> .order_by('user__profile__last_login_date')
> >> >>>>>>>>>>
> >> >>>>>>>>>> We can't keep user__profile_login_date as a variable as in
> the
> >> >>>>>>>>>> first
> >> >>>>>>>>>> part
> >> >>>>>>>>>> of the
> >> >>>>>>>>>> expression we use a keyword argument, meanwhile in the
> second
> >> >>>>>>>>>> part -
> >> >>>>>>>>>> just
> >> >>>>>>>>>> a
> >> >>>>>>>>>> string. And thus we just have to type query path twice.
> >> >>>>>>>>>>
> >> >>>>>>>>>> 3. Lookup names not natural to Python language and require
> to
> >> >>>>>>>>>> be
> >> >>>>>>>>>> remembered or
> >> >>>>>>>>>> looked up in documentation. For example, "__gte" or "__lte"
> >> >>>>>>>>>> lookups
> >> >>>>>>>>>> tend
> >> >>>>>>>>>> to be
> >> >>>>>>>>>> confused with "ge" and "le" due to similarity to methods
> >> >>>>>>>>>> "__ge__"
> >> >>>>>>>>>> and
> >> >>>>>>>>>> "__le__".
> >> >>>>>>>>>>
> >> >>>>>>>>>> 4. Lookup keywords limited to a single argument only, very
> >> >>>>>>>>>> inconvenient
> >> >>>>>>>>>> when
> >> >>>>>>>>>> necessary to filter objects by range.
> >> >>>>>>>>>>
> >> >>>>>>>>>> I was thinking a lot trying to solve those issues, keeping
> in
> >> >>>>>>>>>> mind
> >> >>>>>>>>>> Django
> >> >>>>>>>>>> approaches. Finally I came up with solution to extend Q
> objects
> >> >>>>>>>>>> with
> >> >>>>>>>>>> dot
> >> >>>>>>>>>> expression syntax:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> GameSession.objecs.filter(Q.user.profile.last_login_date
> >=
> >> >>>>>>>>>>>>> yesterday)
> >> >>>>>>>>>>
> >> >>>>>>>>>> Q is a factory instance for old-style Q objects. Accessing
> >> >>>>>>>>>> attribute
> >> >>>>>>>>>> by
> >> >>>>>>>>>> dot
> >> >>>>>>>>>> returns a child factory, calling factory will instantiate
> >> >>>>>>>>>> old-style Q
> >> >>>>>>>>>> object.
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q
> >> >>>>>>>>>> <QFactory object at 0x7f407298ee10>
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q.user.profile
> >> >>>>>>>>>> <QFactory object at 0x7f40765da310>
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q(user__name='Bob')
> >> >>>>>>>>>> <Q: (AND: ('user__name', 'Bob'))>
> >> >>>>>>>>>>
> >> >>>>>>>>>> It overrides operators, so comparing factory with value
> returns
> >> >>>>>>>>>> a
> >> >>>>>>>>>> related
> >> >>>>>>>>>> Q
> >> >>>>>>>>>> object:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q.user.name == 'Bob'
> >> >>>>>>>>>> <Q: (AND: ('user__name', 'Bob'))>
> >> >>>>>>>>>>
> >> >>>>>>>>>> Factory has several helper functions for lookups which
> aren't
> >> >>>>>>>>>> related
> >> >>>>>>>>>> to
> >> >>>>>>>>>> any
> >> >>>>>>>>>> Python operators directly:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q.user.name.icontains('Bob')
> >> >>>>>>>>>> <Q: (AND: ('user__name__icontains', 'Bob'))>
> >> >>>>>>>>>>
> >> >>>>>>>>>> And helper to get query path as string, which requred by
> >> >>>>>>>>>> order_by
> >> >>>>>>>>>> or
> >> >>>>>>>>>> select_related queryset methods:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q.user.profile.last_login_date.get_path()
> >> >>>>>>>>>> 'user__profile__last_login_date'
> >> >>>>>>>>>>
> >> >>>>>>>>>> You can check implementation and more examples here
> >> >>>>>>>>>> https://github.com/Nepherhotep/django-orm-sugar
> >> >>>>>>>>>>
> >> >>>>>>>>>> How it solves issues:
> >> >>>>>>>>>>
> >> >>>>>>>>>> #1. Dots hard to confuse with underscores
> >> >>>>>>>>>> #2. Query paths can be reused:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> factory = Q.user.profile.last_login_date
> >> >>>>>>>>>>>>> query = GameSession.objects.filter(factory >= yesterday)
> >> >>>>>>>>>>>>> query = query.order_by(factory.get_path())
> >> >>>>>>>>>>
> >> >>>>>>>>>> #3. Not neccessary to remember most of lookup names and use
> >> >>>>>>>>>> comparison
> >> >>>>>>>>>> operators
> >> >>>>>>>>>> instead.
> >> >>>>>>>>>> #4. Possible to use multiple keyword arguments:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> Q.user.profile.last_login_date.in_range(from_date,
> to_date)
> >> >>>>>>>>>> <Q: (AND: ('user__profile__last_login_date__lte',
> from_date),
> >> >>>>>>>>>> ('user__profile__last_login_date__gte', to_date))>
> >> >>>>>>>>>>
> >> >>>>>>>>>>
> >> >>>>>>>>>> This approach looked the best for me due to several reasons:
> >> >>>>>>>>>>
> >> >>>>>>>>>> 1. It's explicit - it doesn't do anything but generating
> >> >>>>>>>>>> appropriate
> >> >>>>>>>>>> Q
> >> >>>>>>>>>> object.
> >> >>>>>>>>>> The result of comparison can be saved as Q object variable.
> >> >>>>>>>>>>
> >> >>>>>>>>>> 2. It's short - variants with using model for that will look
> >> >>>>>>>>>> much
> >> >>>>>>>>>> longer,
> >> >>>>>>>>>> when
> >> >>>>>>>>>> joining two or more filters:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> GameSession.objects.user.profile_last_login_date >=
> >> >>>>>>>>>>>>> yesterday
> >> >>>>>>>>>>>>> #
> >> >>>>>>>>>>>>> awkward
> >> >>>>>>>>>>
> >> >>>>>>>>>> 3. Implementation will not require to change querset manager
> or
> >> >>>>>>>>>> model
> >> >>>>>>>>>> classes
> >> >>>>>>>>>>
> >> >>>>>>>>>> 4. Will still allow to use filters and Q class in the old
> way:
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>> q = Q(user__profile__last_login_date__gte=yesterday)
> >> >>>>>>>>>>
> >> >>>>>>>>>> or
> >> >>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> >> >>>>>>>>>>>>>
> GameSession.objects.filter(user__profile__last_login_date__gte=yesterday)
> >> >>>>>>>>>>
> >> >>>>>>>>>> I'd like to make it as a part of Django ORM syntax and it
> will
> >> >>>>>>>>>> not be
> >> >>>>>>>>>> hard to
> >> >>>>>>>>>> do, especially taking into account the library is already
> done
> >> >>>>>>>>>> and
> >> >>>>>>>>>> working.
> >> >>>>>>>>>> Anyway, I need your thought about the idea in general, as
> well
> >> >>>>>>>>>> as
> >> >>>>>>>>>> about
> >> >>>>>>>>>> particular things like chosen method names - "get_path",
> >> >>>>>>>>>> "in_range"
> >> >>>>>>>>>> and
> >> >>>>>>>>>> etc.
> >> >>>>>>>>>> As next step I can create a ticket in the issue tracker, or
> >> >>>>>>>>>> prepare
> >> >>>>>>>>>> DEP
> >> >>>>>>>>>> first.
> >> >>>>>>>>>> In latter case I need to find a shepherd to work with.
> >> >>>>>>>>>>
> >> >>>>>>>>>> Best regards,
> >> >>>>>>>>>> Alexey
> >> >>>>>>>>
> >> >>>>>>>> --
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> >> >>>>>>>>
> >> >>>>>>>>
> >> >>>>>>>>
> >> >>>>>>>>
> https://groups.google.com/d/msgid/django-developers/3bad8371-f9b4-47ff-a681-0108b320e9b5%40googlegroups.com.
>
>
> >> >>>>>>>>
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