Commit e1427cc6 authored by Markus Holtermann's avatar Markus Holtermann
Browse files

Fixed #24590 -- Cached calls to swappable_setting. 

Moved the lookup in Field.swappable_setting to Apps, and added
an lru_cache to cache the results.

Refs #24743

Thanks Marten Kenbeek for the initial work on the patch. Thanks Aymeric
Augustin and Tim Graham for the review.
parent 91f701f4

django/apps/registry.py

+22 −0
Original line number Diff line number Diff line
@@ -260,6 +260,28 @@ class Apps(object): 
                "Model '%s.%s' not registered." % (app_label, model_name))

        return model



    @lru_cache.lru_cache(maxsize=None)

    def get_swappable_settings_name(self, to_string):

        """

        For a given model string (e.g. "auth.User"), return the name of the

        corresponding settings name if it refers to a swappable model. If the

        referred model is not swappable, return None.



        This method is decorated with lru_cache because it's performance

        critical when it comes to migrations. Since the swappable settings don't

        change after Django has loaded the settings, there is no reason to get

        the respective settings attribute over and over again.

        """

        for model in self.get_models(include_swapped=True):

            swapped = model._meta.swapped

            # Is this model swapped out for the model given by to_string?

            if swapped and swapped == to_string:

                return model._meta.swappable

            # Is this model swappable and the one given by to_string?

            if model._meta.swappable and model._meta.label == to_string:

                return model._meta.swappable

        return None



    def set_available_apps(self, available):

        """

        Restricts the set of installed apps used by get_app_config[s].

django/db/models/fields/related.py

+2 −11
Original line number Diff line number Diff line
@@ -314,17 +314,8 @@ class RelatedField(Field): 
            if isinstance(self.remote_field.model, six.string_types):

                to_string = self.remote_field.model

            else:

                to_string = "%s.%s" % (

                    self.remote_field.model._meta.app_label,

                    self.remote_field.model._meta.object_name,

                )

            # See if anything swapped/swappable matches

            for model in apps.get_models(include_swapped=True):

                if model._meta.swapped:

                    if model._meta.swapped == to_string:

                        return model._meta.swappable

                if ("%s.%s" % (model._meta.app_label, model._meta.object_name)) == to_string and model._meta.swappable:

                    return model._meta.swappable

                to_string = self.remote_field.model._meta.label

            return apps.get_swappable_settings_name(to_string)

        return None



    def set_attributes_from_rel(self):

django/db/models/options.py

+1 −1
Original line number Diff line number Diff line
@@ -396,7 +396,7 @@ class Options(object): 
                    # or as part of validation.

                    return swapped_for



                if '%s.%s' % (swapped_label, swapped_object.lower()) not in (None, self.label_lower):

                if '%s.%s' % (swapped_label, swapped_object.lower()) != self.label_lower:

                    return swapped_for

        return None

django/test/utils.py

+11 −1
Original line number Diff line number Diff line
@@ -29,7 +29,7 @@ except ImportError: 




__all__ = (

    'Approximate', 'ContextList', 'get_runner',

    'Approximate', 'ContextList', 'isolate_lru_cache', 'get_runner',

    'modify_settings', 'override_settings',

    'requires_tz_support',

    'setup_test_environment', 'teardown_test_environment',
@@ -503,6 +503,16 @@ def extend_sys_path(*paths): 
        sys.path = _orig_sys_path





@contextmanager

def isolate_lru_cache(lru_cache_object):

    """Clear the cache of an LRU cache object on entering and exiting."""

    lru_cache_object.cache_clear()

    try:

        yield

    finally:

        lru_cache_object.cache_clear()





@contextmanager

def captured_output(stream_name):

    """Return a context manager used by captured_stdout/stdin/stderr

tests/field_deconstruction/tests.py

+20 −16
Original line number Diff line number Diff line 
from __future__ import unicode_literals



from django.apps import apps

from django.db import models

from django.test import SimpleTestCase, override_settings

from django.test.utils import isolate_lru_cache

from django.utils import six
@@ -219,6 +221,7 @@ class FieldDeconstructionTests(SimpleTestCase): 


    @override_settings(AUTH_USER_MODEL="auth.Permission")

    def test_foreign_key_swapped(self):

        with isolate_lru_cache(apps.get_swappable_settings_name):

            # It doesn't matter that we swapped out user for permission;

            # there's no validation. We just want to check the setting stuff works.

            field = models.ForeignKey("auth.Permission", models.CASCADE)
@@ -297,6 +300,7 @@ class FieldDeconstructionTests(SimpleTestCase): 


    @override_settings(AUTH_USER_MODEL="auth.Permission")

    def test_many_to_many_field_swapped(self):

        with isolate_lru_cache(apps.get_swappable_settings_name):

            # It doesn't matter that we swapped out user for permission;

            # there's no validation. We just want to check the setting stuff works.

            field = models.ManyToManyField("auth.Permission")