Fixed #36273 -- Moved Index system checks from Model to Index.check().

3 files changed, 111 insertions, 97 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index eaedd48748..72ba0471a4 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -2115,93 +2115,13 @@ class Model(AltersData, metaclass=ModelBase):
 
     @classmethod
     def _check_indexes(cls, databases):
-        """Check fields, names, and conditions of indexes."""
         errors = []
-        references = set()
-        for index in cls._meta.indexes:
-            # Index name can't start with an underscore or a number, restricted
-            # for cross-database compatibility with Oracle.
-            if index.name[0] == "_" or index.name[0].isdigit():
-                errors.append(
-                    checks.Error(
-                        "The index name '%s' cannot start with an underscore "
-                        "or a number." % index.name,
-                        obj=cls,
-                        id="models.E033",
-                    ),
-                )
-            if len(index.name) > index.max_name_length:
-                errors.append(
-                    checks.Error(
-                        "The index name '%s' cannot be longer than %d "
-                        "characters." % (index.name, index.max_name_length),
-                        obj=cls,
-                        id="models.E034",
-                    ),
-                )
-            if index.contains_expressions:
-                for expression in index.expressions:
-                    references.update(
-                        ref[0] for ref in cls._get_expr_references(expression)
-                    )
         for db in databases:
             if not router.allow_migrate_model(db, cls):
                 continue
             connection = connections[db]
-            if not (
-                connection.features.supports_partial_indexes
-                or "supports_partial_indexes" in cls._meta.required_db_features
-            ) and any(index.condition is not None for index in cls._meta.indexes):
-                errors.append(
-                    checks.Warning(
-                        "%s does not support indexes with conditions."
-                        % connection.display_name,
-                        hint=(
-                            "Conditions will be ignored. Silence this warning "
-                            "if you don't care about it."
-                        ),
-                        obj=cls,
-                        id="models.W037",
-                    )
-                )
-            if not (
-                connection.features.supports_covering_indexes
-                or "supports_covering_indexes" in cls._meta.required_db_features
-            ) and any(index.include for index in cls._meta.indexes):
-                errors.append(
-                    checks.Warning(
-                        "%s does not support indexes with non-key columns."
-                        % connection.display_name,
-                        hint=(
-                            "Non-key columns will be ignored. Silence this "
-                            "warning if you don't care about it."
-                        ),
-                        obj=cls,
-                        id="models.W040",
-                    )
-                )
-            if not (
-                connection.features.supports_expression_indexes
-                or "supports_expression_indexes" in cls._meta.required_db_features
-            ) and any(index.contains_expressions for index in cls._meta.indexes):
-                errors.append(
-                    checks.Warning(
-                        "%s does not support indexes on expressions."
-                        % connection.display_name,
-                        hint=(
-                            "An index won't be created. Silence this warning "
-                            "if you don't care about it."
-                        ),
-                        obj=cls,
-                        id="models.W043",
-                    )
-                )
-        fields = [
-            field for index in cls._meta.indexes for field, _ in index.fields_orders
-        ]
-        fields += [include for index in cls._meta.indexes for include in index.include]
-        fields += references
-        errors.extend(cls._check_local_fields(fields, "indexes"))
+            for index in cls._meta.indexes:
+                errors.extend(index.check(cls, connection))
         return errors
 
     @classmethod
diff --git a/django/db/models/indexes.py b/django/db/models/indexes.py
index 7bea0a663a..176f719fe5 100644
--- a/django/db/models/indexes.py
+++ b/django/db/models/indexes.py
@@ -1,5 +1,6 @@
 from types import NoneType
 
+from django.core import checks
 from django.db.backends.utils import names_digest, split_identifier
 from django.db.models.expressions import Col, ExpressionList, F, Func, OrderBy
 from django.db.models.functions import Collate
@@ -82,6 +83,92 @@ class Index:
     def contains_expressions(self):
         return bool(self.expressions)
 
+    def check(self, model, connection):
+        """Check fields, names, and conditions of indexes."""
+        errors = []
+        # Index name can't start with an underscore or a number (restricted
+        # for cross-database compatibility with Oracle)
+        if self.name[0] == "_" or self.name[0].isdigit():
+            errors.append(
+                checks.Error(
+                    "The index name '%s' cannot start with an underscore "
+                    "or a number." % self.name,
+                    obj=model,
+                    id="models.E033",
+                ),
+            )
+        if len(self.name) > self.max_name_length:
+            errors.append(
+                checks.Error(
+                    "The index name '%s' cannot be longer than %d "
+                    "characters." % (self.name, self.max_name_length),
+                    obj=model,
+                    id="models.E034",
+                ),
+            )
+        references = set()
+        if self.contains_expressions:
+            for expression in self.expressions:
+                references.update(
+                    ref[0] for ref in model._get_expr_references(expression)
+                )
+        errors.extend(
+            model._check_local_fields(
+                {*self.fields, *self.include, *references}, "indexes"
+            )
+        )
+        # Database-feature checks:
+        required_db_features = model._meta.required_db_features
+        if not (
+            connection.features.supports_partial_indexes
+            or "supports_partial_indexes" in required_db_features
+        ) and any(self.condition is not None for index in model._meta.indexes):
+            errors.append(
+                checks.Warning(
+                    "%s does not support indexes with conditions."
+                    % connection.display_name,
+                    hint=(
+                        "Conditions will be ignored. Silence this warning "
+                        "if you don't care about it."
+                    ),
+                    obj=model,
+                    id="models.W037",
+                )
+            )
+        if not (
+            connection.features.supports_covering_indexes
+            or "supports_covering_indexes" in required_db_features
+        ) and any(index.include for index in model._meta.indexes):
+            errors.append(
+                checks.Warning(
+                    "%s does not support indexes with non-key columns."
+                    % connection.display_name,
+                    hint=(
+                        "Non-key columns will be ignored. Silence this "
+                        "warning if you don't care about it."
+                    ),
+                    obj=model,
+                    id="models.W040",
+                )
+            )
+        if not (
+            connection.features.supports_expression_indexes
+            or "supports_expression_indexes" in required_db_features
+        ) and any(index.contains_expressions for index in model._meta.indexes):
+            errors.append(
+                checks.Warning(
+                    "%s does not support indexes on expressions."
+                    % connection.display_name,
+                    hint=(
+                        "An index won't be created. Silence this warning "
+                        "if you don't care about it."
+                    ),
+                    obj=model,
+                    id="models.W043",
+                )
+            )
+        return errors
+
     def _get_condition_sql(self, model, schema_editor):
         if self.condition is None:
             return None
diff --git a/tests/invalid_models_tests/test_models.py b/tests/invalid_models_tests/test_models.py
index c44fe56f89..faa0db9da7 100644
--- a/tests/invalid_models_tests/test_models.py
+++ b/tests/invalid_models_tests/test_models.py
@@ -175,7 +175,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(fields=["missing_field"], name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to the nonexistent field 'missing_field'.",
@@ -193,7 +193,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(fields=["m2m"], name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to a ManyToManyField 'm2m', but "
@@ -215,7 +215,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(fields=["field2", "field1"], name="name")]
 
         self.assertEqual(
-            Bar.check(),
+            Bar.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to field 'field1' which is not local to "
@@ -244,7 +244,7 @@ class IndexesTests(TestCase):
                     models.Index(fields=["foo_1_id", "foo_2"], name="index_name")
                 ]
 
-        self.assertEqual(Bar.check(), [])
+        self.assertEqual(Bar.check(databases=self.databases), [])
 
     def test_pointing_to_composite_primary_key(self):
         class Model(models.Model):
@@ -256,7 +256,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(fields=["pk", "name"], name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to a CompositePrimaryKey 'pk', but "
@@ -276,7 +276,7 @@ class IndexesTests(TestCase):
                 ]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "The index name '%sindex_name' cannot start with an "
@@ -296,7 +296,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(fields=["id"], name=index_name)]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "The index name '%s' cannot be longer than 30 characters."
@@ -499,7 +499,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(fields=["name"], include=["pk"], name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to a CompositePrimaryKey 'pk', but "
@@ -539,6 +539,7 @@ class IndexesTests(TestCase):
 
         self.assertEqual(Model.check(databases=self.databases), [])
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_complex_expression_custom_lookup(self):
         class Model(models.Model):
             height = models.IntegerField()
@@ -554,15 +555,16 @@ class IndexesTests(TestCase):
                 ]
 
         with register_lookup(models.IntegerField, Abs):
-            self.assertEqual(Model.check(), [])
+            self.assertEqual(Model.check(databases=self.databases), [])
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_pointing_to_missing_field(self):
         class Model(models.Model):
             class Meta:
                 indexes = [models.Index(Lower("missing_field").desc(), name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to the nonexistent field 'missing_field'.",
@@ -572,6 +574,7 @@ class IndexesTests(TestCase):
             ],
         )
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_pointing_to_missing_field_nested(self):
         class Model(models.Model):
             class Meta:
@@ -580,7 +583,7 @@ class IndexesTests(TestCase):
                 ]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to the nonexistent field 'missing_field'.",
@@ -590,6 +593,7 @@ class IndexesTests(TestCase):
             ],
         )
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_pointing_to_m2m_field(self):
         class Model(models.Model):
             m2m = models.ManyToManyField("self")
@@ -598,7 +602,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(Lower("m2m"), name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to a ManyToManyField 'm2m', but "
@@ -609,6 +613,7 @@ class IndexesTests(TestCase):
             ],
         )
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_pointing_to_non_local_field(self):
         class Foo(models.Model):
             field1 = models.CharField(max_length=15)
@@ -618,7 +623,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(Lower("field1"), name="name")]
 
         self.assertEqual(
-            Bar.check(),
+            Bar.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to field 'field1' which is not local to "
@@ -630,6 +635,7 @@ class IndexesTests(TestCase):
             ],
         )
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_pointing_to_fk(self):
         class Foo(models.Model):
             pass
@@ -643,8 +649,9 @@ class IndexesTests(TestCase):
                     models.Index(Lower("foo_1_id"), Lower("foo_2"), name="index_name"),
                 ]
 
-        self.assertEqual(Bar.check(), [])
+        self.assertEqual(Bar.check(databases=self.databases), [])
 
+    @skipUnlessDBFeature("supports_expression_indexes")
     def test_func_index_pointing_to_composite_primary_key(self):
         class Model(models.Model):
             pk = models.CompositePrimaryKey("version", "name")
@@ -655,7 +662,7 @@ class IndexesTests(TestCase):
                 indexes = [models.Index(Abs("pk"), name="name")]
 
         self.assertEqual(
-            Model.check(),
+            Model.check(databases=self.databases),
             [
                 Error(
                     "'indexes' refers to a CompositePrimaryKey 'pk', but "