From 2fb872e56f064361c2cd4674c0f23cd419994d82 Mon Sep 17 00:00:00 2001
From: Simon Charette <simon.charette@zapier.com>
Date: Sun, 11 Aug 2019 21:46:23 -0400
Subject: [PATCH] Refs #23879 -- Made introspection respect
 required_db_features.

---
 django/db/backends/base/introspection.py | 64 ++++++++++++------------
 1 file changed, 31 insertions(+), 33 deletions(-)

diff --git a/django/db/backends/base/introspection.py b/django/db/backends/base/introspection.py
index fb362eed1e..29807dfe98 100644
--- a/django/db/backends/base/introspection.py
+++ b/django/db/backends/base/introspection.py
@@ -54,6 +54,16 @@ class BaseDatabaseIntrospection:
         """
         raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_table_list() method')
 
+    def get_migratable_models(self):
+        from django.apps import apps
+        from django.db import router
+        return (
+            model
+            for app_config in apps.get_app_configs()
+            for model in router.get_migratable_models(app_config, self.connection.alias)
+            if model._meta.can_migrate(self.connection)
+        )
+
     def django_table_names(self, only_existing=False, include_views=True):
         """
         Return a list of all table names that have associated Django models and
@@ -61,18 +71,15 @@ class BaseDatabaseIntrospection:
 
         If only_existing is True, include only the tables in the database.
         """
-        from django.apps import apps
-        from django.db import router
         tables = set()
-        for app_config in apps.get_app_configs():
-            for model in router.get_migratable_models(app_config, self.connection.alias):
-                if not model._meta.managed:
-                    continue
-                tables.add(model._meta.db_table)
-                tables.update(
-                    f.m2m_db_table() for f in model._meta.local_many_to_many
-                    if f.remote_field.through._meta.managed
-                )
+        for model in self.get_migratable_models():
+            if not model._meta.managed:
+                continue
+            tables.add(model._meta.db_table)
+            tables.update(
+                f.m2m_db_table() for f in model._meta.local_many_to_many
+                if f.remote_field.through._meta.managed
+            )
         tables = list(tables)
         if only_existing:
             existing_tables = set(self.table_names(include_views=include_views))
@@ -88,14 +95,9 @@ class BaseDatabaseIntrospection:
         Return a set of all models represented by the provided list of table
         names.
         """
-        from django.apps import apps
-        from django.db import router
-        all_models = []
-        for app_config in apps.get_app_configs():
-            all_models.extend(router.get_migratable_models(app_config, self.connection.alias))
         tables = set(map(self.identifier_converter, tables))
         return {
-            m for m in all_models
+            m for m in self.get_migratable_models()
             if self.identifier_converter(m._meta.db_table) in tables
         }
 
@@ -104,24 +106,20 @@ class BaseDatabaseIntrospection:
         Return a list of information about all DB sequences for all models in
         all apps.
         """
-        from django.apps import apps
-        from django.db import router
-
         sequence_list = []
         with self.connection.cursor() as cursor:
-            for app_config in apps.get_app_configs():
-                for model in router.get_migratable_models(app_config, self.connection.alias):
-                    if not model._meta.managed:
-                        continue
-                    if model._meta.swapped:
-                        continue
-                    sequence_list.extend(self.get_sequences(cursor, model._meta.db_table, model._meta.local_fields))
-                    for f in model._meta.local_many_to_many:
-                        # If this is an m2m using an intermediate table,
-                        # we don't need to reset the sequence.
-                        if f.remote_field.through._meta.auto_created:
-                            sequence = self.get_sequences(cursor, f.m2m_db_table())
-                            sequence_list.extend(sequence or [{'table': f.m2m_db_table(), 'column': None}])
+            for model in self.get_migratable_models():
+                if not model._meta.managed:
+                    continue
+                if model._meta.swapped:
+                    continue
+                sequence_list.extend(self.get_sequences(cursor, model._meta.db_table, model._meta.local_fields))
+                for f in model._meta.local_many_to_many:
+                    # If this is an m2m using an intermediate table,
+                    # we don't need to reset the sequence.
+                    if f.remote_field.through._meta.auto_created:
+                        sequence = self.get_sequences(cursor, f.m2m_db_table())
+                        sequence_list.extend(sequence or [{'table': f.m2m_db_table(), 'column': None}])
         return sequence_list
 
     def get_sequences(self, cursor, table_name, table_fields=()):