Proposal: filter by multiple values, case-insensitive

[Jeremy Nauta]

Hi all, I'd like to propose a new django filter: *__iin*. As the name 
implies, this filter finds results that match one of the given values, 
ignoring case. In other words, this is a hybrid of *__in *and *__iexact*.

It surprises me that there are filters for* qs.filter(field__iexact='text')*
, *qs.filter(field__icontains='text')*, and *qs.filter(field__in=[**'text']*
*)*, yet there is no *qs.filter(field__iin=[**'text']**)* filter.

I've made a POC for this field in postgres and it seems quite 
straightforward. I'd be happy to try porting into the Django codebase, but 
first I wanted to see if there is interest and/or feedback! Please let me 
know what you think.


























*from django.db.models import Fieldfrom django.db.models.lookups import 
In@Field.register_lookupclass IIn(In):"""Case-insensitive version 
of `__in` filters. Adapted from `In` and `IExact` transformers."""
lookup_name = 'iin'def process_lhs(self, *args, **kwargs):sql, 
params = super().process_lhs(*args, **kwargs)sql = f'LOWER({sql})'  
  return sql, paramsdef process_rhs(self, qn, connection):
rhs, params = super().process_rhs(qn, connection)params = 
tuple(p.lower() for p in params)return rhs, params*

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Re: Generated Field

[Jeremy Nauta]

I'd love to help implement this if we can find a rough syntax! I've made a 
proof of concept in Postgres, and there are two outstanding limitations to 
address:

- The generated field value is not set until the model is reloaded from the 
database
- The `GENERATED ALWAYS` expression requires an argument to be injected in 
the the sql expression, but this is not currently possible

*from django.db.backends.utils import CursorWrapper*

*from django.db.models import Expression, Field*

*from django.db.models.sql import Query*



*class GeneratedField(Field):*

*"""*

*Wrapper field used to support generated columns in postgres.*

*"""*


*def __init__(self, expression: Expression, db_collation: str = None, 
*args, **kwargs):*

*"""*

*:param expression: DB expression used to calculate the 
auto-generated field value*

*"""*


*self.expression = expression*

*self.db_collation = db_collation*


*kwargs['editable'] = False  # This field can never be edited*

*kwargs['blank'] = True  # This field never requires a value to be 
set*

*kwargs['null'] = True  # This field never requires a value to be 
set*


*super().__init__(*args, **kwargs)*


*def _compile_expression(self, cursor: CursorWrapper, sql: str, params: 
dict):*

*"""*

*Compiles SQL and its associated parameters into a full SQL query. 
Usually sql params are kept*

*separate until `cursor.execute()` is called, but this is not 
possible since this function*

*must return a single sql string.*

*"""*


*return cursor.mogrify(sql, params).decode()*


*def db_type(self, connection):*

*"""*

*Called when calculating SQL to create DB column (e.g. DB 
migrations)*

*
https://docs.djangoproject.com/en/4.1/ref/models/fields/#django.db.models.Field.db_type*

*"""*


*db_type = 
self.expression.output_field.db_type(connection=connection)*


*# Convert any F() references to concrete field names*

*query = Query(model=self.model, alias_cols=False)*

*expression = self.expression.resolve_expression(query, 
allow_joins=False)*


*# Compile expression into SQL*

*expression_sql, params = expression.as_sql(*

*compiler=connection.ops.compiler('SQLCompiler')(*

*query, connection=connection, using=None*

*),*

*connection=connection,*

*)*


*with connection.cursor() as cursor:*

*expression_sql = self._compile_expression(*

*cursor=cursor, sql=expression_sql, params=params*

*)*


*return f'{db_type} GENERATED ALWAYS AS ({expression_sql}) STORED'*


*def rel_db_type(self, connection):*

*"""*

*Called when calculating SQL to reference DB column*

*
https://docs.djangoproject.com/en/4.1/ref/models/fields/#django.db.models.Field.rel_db_type*

*"""*

*return self.expression.output_field.db_type(connection=connection)*


*def deconstruct(self):*

*"""*

*Add custom field properties to allow migrations to deconstruct 
field*

*
https://docs.djangoproject.com/en/4.1/ref/models/fields/#django.db.models.Field.deconstruct*

*"""*

*name, path, args, kwargs = super().deconstruct()*

*kwargs['expression'] = self.expression*

*if self.db_collation is not None:*

*kwargs['db_collation'] = self.db_collation*

*return name, path, args, kwargs*



*class GeneratedFieldQuerysetMixin:*

*"""*

*Must be added to queryset classes*

*"""*


*def _insert(self, objs, fields, *args, **kwargs):*

*if getattr(self.model, '_generated_fields', None) and fields:*

*# Don't include generated fields when performing a 
`model.objects.bulk_create()`*

*fields = [f for f in fields if f not in 
self.model._generated_fields()]*


*return super()._insert(objs, fields, *args, **kwargs)*



*class GeneratedFieldModelMixin:*

*"""*

*Must be added to model class*

*"""*


*def _generated_fields(cls) -> list[Field]:*


*"""*

*:return all fields of the model that are generated*

*"""*


*return [*

*f*

*for f in cls._meta.fields*

*if isinstance(f, GeneratedField)*

*]*


*def _do_insert(self, manager, using, fields, *args, **kwargs):*

*generated_fields = self._generated_fields()*

*if generated_fields and fields:*

*# Don't include generated fields when performing a `save()` or 
`create()`*

*fields = [f for f in fields if f not in generated_fields]*


*return super()._do_insert(manager, using, fields, *args, **kwargs)*


*def _do_update(self, base_qs, using, pk_val, values, *args, **kwargs):*

*generated_fields = self._generated_fields()*

*

Re: Generated Field

[Jeremy Nauta]

I have implemented a first draft for this feature! Feedback and ideas are 
greatly appreciated.

https://github.com/django/django/pull/16417
https://code.djangoproject.com/ticket/34238

On Saturday, December 24, 2022 at 8:56:38 p.m. UTC-7 schinckel wrote:

> I believe there are a bunch of similarities between the requirements of 
> generated fields and my project django-shared-property: 
> https://django-shared-property.readthedocs.io/en/latest/
>
> On Sunday, December 25, 2022 at 10:23:10 AM UTC+10:30 jeremy...@gmail.com 
> wrote:
>
>> I'd love to help implement this if we can find a rough syntax! I've made 
>> a proof of concept in Postgres, and there are two outstanding limitations 
>> to address:
>>
>> - The generated field value is not set until the model is reloaded from 
>> the database
>> - The `GENERATED ALWAYS` expression requires an argument to be injected 
>> in the the sql expression, but this is not currently possible
>>
>> *from django.db.backends.utils import CursorWrapper*
>>
>> *from django.db.models import Expression, Field*
>>
>> *from django.db.models.sql import Query*
>>
>>
>>
>> *class GeneratedField(Field):*
>>
>> *"""*
>>
>> *Wrapper field used to support generated columns in postgres.*
>>
>> *"""*
>>
>>
>> *def __init__(self, expression: Expression, db_collation: str = None, 
>> *args, **kwargs):*
>>
>> *"""*
>>
>> *:param expression: DB expression used to calculate the 
>> auto-generated field value*
>>
>> *"""*
>>
>>
>> *self.expression = expression*
>>
>> *self.db_collation = db_collation*
>>
>>
>> *kwargs['editable'] = False  # This field can never be edited*
>>
>> *kwargs['blank'] = True  # This field never requires a value to 
>> be set*
>>
>> *kwargs['null'] = True  # This field never requires a value to be 
>> set*
>>
>>
>> *super().__init__(*args, **kwargs)*
>>
>>
>> *def _compile_expression(self, cursor: CursorWrapper, sql: str, 
>> params: dict):*
>>
>> *"""*
>>
>> *Compiles SQL and its associated parameters into a full SQL 
>> query. Usually sql params are kept*
>>
>> *separate until `cursor.execute()` is called, but this is not 
>> possible since this function*
>>
>> *must return a single sql string.*
>>
>> *"""*
>>
>>
>> *return cursor.mogrify(sql, params).decode()*
>>
>>
>> *def db_type(self, connection):*
>>
>> *"""*
>>
>> *Called when calculating SQL to create DB column (e.g. DB 
>> migrations)*
>>
>> *
>> https://docs.djangoproject.com/en/4.1/ref/models/fields/#django.db.models.Field.db_type
>>  
>> *
>>
>> *"""*
>>
>>
>> *db_type = 
>> self.expression.output_field.db_type(connection=connection)*
>>
>>
>> *# Convert any F() references to concrete field names*
>>
>> *query = Query(model=self.model, alias_cols=False)*
>>
>> *expression = self.expression.resolve_expression(query, 
>> allow_joins=False)*
>>
>>
>> *# Compile expression into SQL*
>>
>> *expression_sql, params = expression.as_sql(*
>>
>> *compiler=connection.ops.compiler('SQLCompiler')(*
>>
>> *query, connection=connection, using=None*
>>
>> *),*
>>
>> *connection=connection,*
>>
>> *)*
>>
>>
>> *with connection.cursor() as cursor:*
>>
>> *expression_sql = self._compile_expression(*
>>
>> *cursor=cursor, sql=expression_sql, params=params*
>>
>> *)*
>>
>>
>> *return f'{db_type} GENERATED ALWAYS AS ({expression_sql}) 
>> STORED'*
>>
>>
>> *def rel_db_type(self, connection):*
>>
>> *"""*
>>
>> *Called when calculating SQL to reference DB column*
>>
>> *
>> https://docs.djangoproject.com/en/4.1/ref/models/fields/#django.db.models.Field.rel_db_type
>>  
>> *
>>
>> *"""*
>>
>> *return 
>> self.expression.output_field.db_type(connection=connection)*
>>
>>
>> *def deconstruct(self):*
>>
>> *"""*
>>
>> *Add custom field properties to allow migrations to deconstruct 
>> field*
>>
>> *
>> https://docs.djangoproject.com/en/4.1/ref/models/fields/#django.db.models.Field.deconstruct
>>  
>> *
>>
>> *"""*
>>
>> *name, path, args, kwargs = super().deconstruct()*
>>
>> *kwargs['expression'] = self.expression*
>>
>> *if self.db_collation is not None:*
>>
>> *kwargs['db_collation'] = self.db_collation*
>>
>> *return name, path, args, kwargs*
>>
>>
>>
>> *class GeneratedFieldQuerysetMixin:*
>>
>> *"""*
>>
>> *Must be added to queryset classes*
>>
>> *"""*
>>
>>
>> *def _insert(self, 

Re: models.CalculatedField feature

[Jeremy Nauta]

FYI I have posted a tentative first draft of this feature, feedback is 
greatly appreciated!

https://github.com/django/django/pull/16417
https://code.djangoproject.com/ticket/31300

On Saturday, February 3, 2018 at 5:06:08 p.m. UTC-7 raider...@gmail.com 
wrote:

> Hey, 
>
> So has this stalled? Because this looked really great, and I was looking 
> forward to seeing it!
>
>
> On Monday, November 20, 2017 at 10:31:31 PM UTC-5, 
> ilya.ka...@jetbrains.com wrote:
>
>> Thank you all.
>>
>> I've created a feature request 
>> https://code.djangoproject.com/ticket/28822 and will try to implement in 
>> my Django fork next week. I am not Django source code guru, so any help is 
>> welcome:)
>>
>

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