What about the idea to add interface to specify paths with special class or callable?
On Wednesday, August 19, 2015 at 10:49:07 AM UTC+3, Josh Smeaton wrote: > > If I finish the patch in time (I think I have about a month left), then > it'll be included in 1.9. Review and comments on the PR will go a long way > to helping me tidy it up sooner rather than later, so please feel free to > review. > > Regards, > > On Wednesday, 19 August 2015 04:55:21 UTC+10, Alexey Zankevich wrote: >> >> Once Josh completes this patch https://github.com/django/django/pull/5090 >> (.filter method accepting class-based lookups and transforms), it will be >> almost everything required by third-party apps. Is it going to be a part >> of >> Django 1.9, by the way? >> >> Additionally, for pure flexibility, next method and classes need to accept >> either a callable or an object supporting special path interface (for >> example, >> just a single method get_path() returning string path). >> They listed below: >> >> 1. The current methods.select_related, .prefetch_related, .order_by >> 2. Annotation classes Min, Max, Count, Sum >> 3. Future transforms and lookups classes >> >> >> Examples: >> >> >>> path = lambda x: 'user__last_login_date' >> >>> GameSession.objects.all().order_by(path) >> >> or >> >> >>> class LoginDatePath(object): >> ... def get_path(self): >> ... return 'user__last_login_date' >> >>> path = LoginDatePath() >> >>> GameSession.objects.all().order_by(path) >> >> Path generation is a critical part of external query syntax as it used in >> almost all aspects of the ORM, meanwhile each related method accepts >> either a >> string or (in some cases) a specific kind of class - OrderBy for order_by >> method, Prefetch for prefetch_related and etc. >> >> >> On Tuesday, August 18, 2015 at 7:54:48 PM UTC+3, Michael Manfre wrote: >> >> +1 for making it doable for 3rd party apps. >> >> Regards, >> Michael Manfre >> >> On Tue, Aug 18, 2015 at 12:49 PM, Anssi Kääriäinen <akaa...@gmail.com> >> wrote: >> >> I'm still thinking we shouldn't integrate any new query syntax into >> 1.9. Instead lets make it easy to create 3rd party apps that offer >> different querying syntax, and then lets see which solution (if any) >> gets popular enough to be integrated into Django. >> >> - Anssi >> >> >> >> On Tue, Aug 18, 2015 at 5:54 PM, Collin Anderson <cmawe...@gmail.com> >> wrote: >> > Just a quick thought: I could imagine some newbies could get confused >> by the >> > python-like syntax and try to do: >> > >> > Equal(P.user.get_full_name(), 'Bob Someone') >> > >> > I don't think it's not a huge deal, but worth noting. >> > >> > On Tuesday, August 18, 2015 at 8:00:17 AM UTC-4, Alexey Zankevich wrote: >> >> >> >> Hi all, >> >> >> >> Thanks for detailed response. I thought over the described expressions/ >> >> transforms patches and here are my thoughts about the best way to >> >> implement simplified lookups. >> >> >> >> Firstly, I want to describe which properties of the new syntax seem to >> be >> >> important: >> >> >> >> 1. Using Python operators to do basic lookups as it's a natural way in >> >> Python >> >> for that. >> >> >> >> 2. Syntax should be minimalistic for basic lookups, the use of that >> >> approach >> >> will be more noticeable on multiple filter conditions. In other words, >> >> next >> >> syntax is better: >> >> >> >> >>> GameSession.objects.filter(Q.user.profile.last_login.date() == >> >> >>> datetime.now().date) >> >> >> >> than this one >> >> >> >> >>> GameSession.objects.filter(E(F.user.profile.last_login).date() == >> >> >>> datetime.now().date) >> >> >> >> as it requires additional calls, which makes expressions less readable. >> >> >> >> 3. I definitely like the idea of having explicit classes for lookups >> and >> >> transforms and think it's worth to bundle dotted query syntax with the >> >> patch. >> >> Explicit classes will separate functionality and simplify functions >> >> signature >> >> checks. >> >> >> >> I suggest a mixed approach, with next properties. >> >> >> >> 1. We will have a separate class to define query paths (let's call it >> P, >> >> we >> >> can still use F as "field", but having F as multipurpose class may >> confuse >> >> users, as well as implementation may become more complicated). And it >> will >> >> be >> >> the only purpose of the class. Below I'll reference it as "P" no >> matter we >> >> call >> >> it in future. >> >> >> >> 2. Any transforms and lookups will take query string or P class, as >> well >> >> as >> >> existing methods "select_related", "prefetch_related" and "order_by". >> The >> >> simplest implementation will be overriding __str__ method of the path >> >> class >> >> to generate related strings. >> >> >> >> >>> path = P.user.last_login_date >> >> >>> GameSession.objects.all().order_by(path)[:10] >> >> >> >> >>> print(path) >> >> user__last_login_date >> >> >> >> 3. Implement transforms and lookups as classes or functions (not bound >> to >> >> P class): >> >> >> >> >>> GameSession.objects.filter(Unaccent(P.user.location.name) == "Cote >> >> >>> d'Ivoire") >> >> >> >> It will simplify cases with parametrized transforms (ex. mentioned >> >> collate('fi')). >> >> Also eliminate fields collision with util functions like "date", which >> may >> >> be a >> >> so-called field. >> >> >> >> 4. Below is a table describing accepted passed and returned parameters: >> >> >> >> >> +-------------------+---------------------------+----------------------+ >> >> | Class/Function | Allowed Param Types | Comparison Operators >> | >> >> >> +-------------------+---------------------------+----------------------+ >> >> | Transform | str, P, Transform, Lookup | Return lookup >> | >> >> | Lookup | str, P, Transform | Raise exception >> | >> >> | P | | Return lookup >> | >> >> | .order_by | str, P | >> | >> >> | .select_related | str, P | >> | >> >> | .prefetch_related | str, P, Prefetch | >> | >> >> >> +-------------------+---------------------------+----------------------+ >> >> >> >> >> >> Samples: >> >> >> >> >>> P.user.name == 'Bob' >> >> Equal('user__name', 'Bob') >> >> >> >> >>> Unaccent(P.user.name) >> >> Unaccent('user__name') >> >> >> >> >>> Collate(P.user.name, 'fi') >> >> Collate('user__name', 'fi') >> >> >> >> >>> Unaccent(P.user.name) == 'Bob' >> >> Equal(Unaccent('user__name'), 'Bob') >> >> >> >> >>> Equal(P.user.name, 'Bob') == 'Bob' >> >> Traceback (most recent call last): >> >> File "<stdin>", line 1, in <module> >> >> Exception: Lookups comparison is not allowed >> >> >> >> >>> Contains(P.user.name, 'Bo') # lookup >> >> >>> Date(P.user.last_login_date, datetime.now().date) # transform >> >> >> >> >> >> Questions to discuss and possible pitfalls: >> >> >> >> 1. Handling descended ordering in order_by >> >> >> >> >>> path = P.user.last_login_date >> >> >>> -path >> >> '-user__last_login_date' >> >> >> >> or even >> >> >> >> >>> -p >> >> NegP('user__last_login_date') >> >> >> >> Is it possible path subtraction is required in future by any reason? In >> >> that >> >> case the given approach will be inconvenient. Or may be better to just >> let >> >> users to format desc ordering themselves? >> >> >> >> >>> '-{}'.format(path) >> >> >> >> 2. Don't think it's a big deal, but users might do next thing: >> >> >> >> >>> path = P.user.last_login_date >> >> >>> GameSession.objects.filter(path=today) >> >> Traceback (most recent call last): >> >> File "<console>", line 1, in <module> >> >> FieldError: Cannot resolve keyword 'path' into field. >> >> >> >> At least need to mention it in documentation >> >> >> >> 3. Classes vs factory functions: >> >> >> >> >>> Equal(P.user.name, 'Bob') >> >> Equal('user__name', 'Bob') >> >> >> >> vs >> >> >> >> >>> equal(P.user.name, 'Bob') >> >> Equal('user__name', 'Bob') >> >> >> >> >> >> If you are fine with described syntax I can start with DEP. >> >> >> >> Regards, >> >> Alexey >> >> >> >> On Monday, August 17, 2015 at 12:26:45 PM UTC+3, Anssi Kääriäinen >> wrote: >> >>> >> >>> I like this idea, too. >> >>> >> >>> The work I and Loic have been doing has been about transforms that can >> >>> accept arguments. I don't see why the two styles couldn't be mixed >> >>> directly. >> >>> >> >>> .filter(Q.user.profile.last_login.date(timezone='Europe/Helsinki') < >> >>> '2015-01-01') >> >>> .filter(Q.user.last_name.collate('fi').unaccent() == 'Kaariainen') >> >>> >> >>> OTOH if you want to use expressions directly, that should be OK, too >> >>> (if you don't mind the non-optimal readability): >> >>> .filter(Exact(unaccent(collate(Q.user.last_name, 'fi'))), >> 'Kaariainen')) >> >>> >> >>> All in all, +1 to working towards these goals. I'm not yet convinced >> >>> we need all this in Django core directly. Maybe we should first try >> >>> these ideas in 3rd party apps, and then pick a proven solution into >> >>> Django core? >> >>> >> >>> - Anssi >> >>> >> >>> On Mon, Aug 17, 2015 at 3:33 AM, Josh Smeaton <josh.s...@gmail.com> >> >>> wrote: >> >>> > Hi Alexey, >> >>> > >> >>> > I find this approach really interesting, and I don't mind the API >> >>> > you've >> >>> > created at all. Even if this doesn't make it into Django, I think >> >>> > there's >> >>> > enough utility in your library that other people would want to use >> it. >> >>> > I'm >> >>> > not going to comment on specifics just yet like method names, >> because I >> >>> > figure that if we can agree on an approach, the bike-shedding can >> come >> >>> > later. >> >>> > >> >>> > So first things first. I think we can all, or at least mostly, agree >> >>> > that >> >>> > having an alternative syntax for building filters is a good idea. >> >>> > String >> >>> > based lookups are cool, and won't go away, but sometimes you want to >> >>> > have >> >>> > greater control over what kind of filter you want to build without >> >>> > having to >> >>> > register global lookups and transforms. I see similarities with >> >>> > prefetch_related. You can provide a string based field lookup, or >> use a >> >>> > Prefetch() object to give users more control over the behaviour of >> the >> >>> > prefetch. >> >>> > >> >>> > I've been working on a patch >> >>> > (https://github.com/django/django/pull/5090) to >> >>> > unify Transforms and Expressions (Func specifically). The work >> behind >> >>> > that >> >>> > can be (and should be) extended to include Lookups -- making them >> fully >> >>> > fledged expression objects. That work will need to happen >> regardless. >> >>> > Once >> >>> > this patch is finished and lands, then we should be able to extend >> >>> > .filter() >> >>> > and .exclude() to allow expressions to be composed as filters: >> >>> > >> >>> > >> >>> > >> GameSession.objects.filter(GreaterThan('user__profile__last_login_date', >> >>> > yesterday)) >> >>> > # or, if last_login was a datetime, and we wanted to compare the >> date >> >>> > part >> >>> > only >> >>> > GameSession.objects.filter(Equal(Date('user__profile__last_login'), >> >>> > datetime.now().date)) >> >>> > # or if we wanted to implement __gt__ and __eq__ etc: >> >>> > GameSession.objects.filter(Date('user__profile__last_login') == >> >>> > datetime.now().date)) >> >>> > >> >>> > Loic and Anssi have also been working on alternative syntaxes >> >>> > (https://github.com/django/django/pull/4953): >> >>> > >> >>> > GameSession.objects.filter(E('user__profile__last_login').date() == >> >>> > datetime.now().date) >> >>> > >> >>> > >> >>> > Article.objects.filter(E('headline').collate('fi') == 'Article1') >> >>> > >> >>> > Both of these approaches still suffer from "the string problem" that >> >>> > you're >> >>> > trying to address, but minimises the final component by extracting >> the >> >>> > lookup and transform components as objects instead. So I think your >> >>> > idea >> >>> > here could nicely coexist: >> >>> > >> >>> > GameSession.objects.filter(Equal(Date(Q.user.profile.last_login), >> >>> > datetime.now().date)) >> >>> > GameSession.objects.filter(E(Q.user.profile.last_login).date() == >> >>> > datetime.now().date) >> >>> > >> >>> > Or, even building this into F expressions rather than Q expressions: >> >>> > >> >>> > GameSession.objects.filter(Equal(Date(F.user.profile.last_login), >> >>> > datetime.now().date)) >> >>> > GameSession.objects.filter(E(F.user.profile.last_login).date() == >> >>> > datetime.now().date) >> >>> > >> >>> > I think it may look better with F objects, considering they are >> Field >> >>> > references, and since the Lookups (Equal/GTE) parts accept F >> >>> > expressions >> >>> > anyway. I'm not too concerned about this particular detail though. >> >>> > >> >>> > A DEP is probably the right way to go here but I wonder if we should >> >>> > expand >> >>> > the scope to include alternative filter syntax as a whole >> >>> > (expressions/callable transforms) as well as the dot field reference >> >>> > notation you've proposed above. Then we can consider how all these >> >>> > things >> >>> > might work together, and clearly document why we've gone one way and >> >>> > not >> >>> > another. Obviously, alternatives can exist outside of core where the >> >>> > API is >> >>> > available. >> >>> > >> >>> > I'll be happy to work as the shepherd if needed. But I'd also like >> some >> >>> > input from Loic and Anssi especially, as well as others in the core >> >>> > team >> >>> > with some interest in the ORM. >> >>> > >> >>> > Regards, >> >>> > >> >>> > >> >>> > On Sunday, 16 August 2015 23:18:26 UTC+10, 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 >> >>> > >> >>> > -- >> >>> > You received this message because you are subscribed to the Google >> >>> > Groups >> >>> > "Django developers (Contributions to Django itself)" group. >> >>> > To unsubscribe from this group and stop receiving emails from it, >> send >> >>> > an >> >>> > email to django-develop...@googlegroups.com. >> >>> > To post to this group, send email to django-d...@googlegroups.com. >> >>> > Visit this group at >> http://groups.google.com/group/django-developers. >> >>> > To view this discussion on the web visit >> >>> > >> >>> > >> https://groups.google.com/d/msgid/django-developers/db4003cb-f366-430c-92c1-8388ff35804b%40googlegroups.com >> . >> >>> > >> >>> > For more options, visit https://groups.google.com/d/optout. >> > >> > -- >> > You received this message because you are subscribed to the Google >> Groups >> > "Django developers (Contributions to Django itself)" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> an >> > email to django-develop...@googlegroups.com. >> > To post to this group, send email to django-d...@googlegroups.com. >> > Visit this group at http://groups.google.com/group/django-developers. >> > To view this discussion on the web visit >> > >> https://groups.google.com/d/msgid/django-developers/1aeba72e-a34a-4b92-8f74-55af0da2671b%40googlegroups.com >> . >> > >> > For more options, visit https://groups.google.com/d/optout. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django developers (Contributions to Django itself)" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to django-develop...@googlegroups.com. >> To post to this group, send email to django-d...@googlegroups.com. >> Visit this group at http://groups.google.com/group/django-developers. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-developers/CALMtK1EgXq3CRW8oseE8Uug7ZH%3DEQpFUEVKbMS-4Z%2B%2BwJXbEAA%40mail.gmail.com >> . >> For more options, visit https://groups.google.com/d/optout. >> >> >> >> >> -- >> GPG Fingerprint: >> >> ... > > -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. 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