Annotated Fields in Case-When

[henadzit]

Description

This PR:

• Enables use of annotations in Case-When, e.g.

IntFields.all()\
  .annotate(intnum_plus_1=F("intnum") + 1)\
  .annotate(bigger_than_10=Case(When(Q(intnum_plus_1__gte=10), then=True), default=False))

• Introduces ResolveContext that holds the information required to resolve expressions
• Fixes Can't use annotated field in CASE-WHEN Clause #1299

Motivation and Context

Django lets you use annotations in Case-When, so it would be nice to have it too.

ResolveContext simplifies the code by incapsulating all the information required for resolving expressions, i.e. the model, the table, annotations and custom filters as opposed to the old way of assigning _annotations and _custom_filters to expressions. I'm planning on using it to resolve F expressions, for instance, to allow referring to related models in F (related issue).

How Has This Been Tested?

• Added tests
• The following snippet can be used to compare the behavior prior and after the changes

import logging
import sys

from tortoise import Tortoise, fields, run_async
from tortoise.models import Model
from tortoise.expressions import F, Q, Case, When

fmt = logging.Formatter(
    fmt="%(asctime)s - %(name)s:%(lineno)d - %(levelname)s - %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
)
sh = logging.StreamHandler(sys.stdout)
sh.setLevel(logging.DEBUG)
sh.setFormatter(fmt)

logger_tortoise = logging.getLogger("tortoise")
logger_tortoise.setLevel(logging.DEBUG)
logger_tortoise.addHandler(sh)


class User(Model):
    value = fields.IntField()


async def main():
    # Initializing Tortoise and creating the schema

    await Tortoise.init(  # type: ignore
        db_url="sqlite://:memory:",
        modules={"models": ["__main__"]},
    )
    await Tortoise.generate_schemas()

    await User.create(value=1)
    await User.create(value=2)

    queryset = User.all()
    queryset = queryset.annotate(
        value2=F("value") + 1,
    )
    queryset = queryset.annotate(
        ignore_priority=Case(
            When(Q(value2=2), then=True),
            default=False,
        ),
    )
    res = await queryset
    for user in res:
        print(user.value, user.value2, user.ignore_priority)


run_async(main())

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[henadzit]

I'm having a hard time to understand why _custom_filters is changed to custom_filters in QuerySet subclasses (same with force_indexes, annotations, etc.). I would love to know that!

[abondar]

Honestly - I don't remember :)

I remember last time I tried to fix it - I ran in some kind of problem related to the fact, that processing of some of this fields have different logic in QuerySet and it's children, so reusing it caused some issues about joins not working properly or something like that

If you have time to experiment with that - you can try to fix it and create PR

[coveralls]

Pull Request Test Coverage Report for Build 11514953088

Details

• 63 of 63 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 89.024%

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Totals
Change from base Build 11435130298:	0.003%
Covered Lines:	5979
Relevant Lines:	6602

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💛 - Coveralls