Fixed #31777 -- Added support for database collations to Char/TextFields.

Thanks Simon Charette and Mariusz Felisiak for reviews.

25 files changed, 544 insertions, 30 deletions

diff --git a/django/core/management/commands/inspectdb.py b/django/core/management/commands/inspectdb.py
index 73e8a19e76..f9b4bfb477 100644
--- a/django/core/management/commands/inspectdb.py
+++ b/django/core/management/commands/inspectdb.py
@@ -247,6 +247,9 @@ class Command(BaseCommand):
         if field_type == 'CharField' and row.internal_size:
             field_params['max_length'] = int(row.internal_size)
 
+        if field_type in {'CharField', 'TextField'} and row.collation:
+            field_params['db_collation'] = row.collation
+
         if field_type == 'DecimalField':
             if row.precision is None or row.scale is None:
                 field_notes.append(
diff --git a/django/db/backends/base/features.py b/django/db/backends/base/features.py
index 3aa0577866..477ae96c8d 100644
--- a/django/db/backends/base/features.py
+++ b/django/db/backends/base/features.py
@@ -302,10 +302,17 @@ class BaseDatabaseFeatures:
     # {'d': [{'f': 'g'}]}?
     json_key_contains_list_matching_requires_list = False
 
+    # Does the backend support column collations?
+    supports_collation_on_charfield = True
+    supports_collation_on_textfield = True
+    # Does the backend support non-deterministic collations?
+    supports_non_deterministic_collations = True
+
     # Collation names for use by the Django test suite.
     test_collations = {
         'ci': None,  # Case-insensitive.
         'cs': None,  # Case-sensitive.
+        'non_default': None,  # Non-default.
         'swedish_ci': None  # Swedish case-insensitive.
     }
 
diff --git a/django/db/backends/base/introspection.py b/django/db/backends/base/introspection.py
index 10c04abece..c8b0e90873 100644
--- a/django/db/backends/base/introspection.py
+++ b/django/db/backends/base/introspection.py
@@ -4,7 +4,11 @@ from collections import namedtuple
 TableInfo = namedtuple('TableInfo', ['name', 'type'])
 
 # Structure returned by the DB-API cursor.description interface (PEP 249)
-FieldInfo = namedtuple('FieldInfo', 'name type_code display_size internal_size precision scale null_ok default')
+FieldInfo = namedtuple(
+    'FieldInfo',
+    'name type_code display_size internal_size precision scale null_ok '
+    'default collation'
+)
 
 
 class BaseDatabaseIntrospection:
diff --git a/django/db/backends/base/schema.py b/django/db/backends/base/schema.py
index 03d8945106..ccb41b2c61 100644
--- a/django/db/backends/base/schema.py
+++ b/django/db/backends/base/schema.py
@@ -61,6 +61,7 @@ class BaseDatabaseSchemaEditor:
     sql_alter_column_not_null = "ALTER COLUMN %(column)s SET NOT NULL"
     sql_alter_column_default = "ALTER COLUMN %(column)s SET DEFAULT %(default)s"
     sql_alter_column_no_default = "ALTER COLUMN %(column)s DROP DEFAULT"
+    sql_alter_column_collate = "ALTER COLUMN %(column)s TYPE %(type)s%(collation)s"
     sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s CASCADE"
     sql_rename_column = "ALTER TABLE %(table)s RENAME COLUMN %(old_column)s TO %(new_column)s"
     sql_update_with_default = "UPDATE %(table)s SET %(column)s = %(default)s WHERE %(column)s IS NULL"
@@ -215,6 +216,10 @@ class BaseDatabaseSchemaEditor:
         # Check for fields that aren't actually columns (e.g. M2M)
         if sql is None:
             return None, None
+        # Collation.
+        collation = getattr(field, 'db_collation', None)
+        if collation:
+            sql += self._collate_sql(collation)
         # Work out nullability
         null = field.null
         # If we were told to include a default value, do so
@@ -676,8 +681,15 @@ class BaseDatabaseSchemaEditor:
         actions = []
         null_actions = []
         post_actions = []
+        # Collation change?
+        old_collation = getattr(old_field, 'db_collation', None)
+        new_collation = getattr(new_field, 'db_collation', None)
+        if old_collation != new_collation:
+            # Collation change handles also a type change.
+            fragment = self._alter_column_collation_sql(model, new_field, new_type, new_collation)
+            actions.append(fragment)
         # Type change?
-        if old_type != new_type:
+        elif old_type != new_type:
             fragment, other_actions = self._alter_column_type_sql(model, old_field, new_field, new_type)
             actions.append(fragment)
             post_actions.extend(other_actions)
@@ -895,6 +907,16 @@ class BaseDatabaseSchemaEditor:
             [],
         )
 
+    def _alter_column_collation_sql(self, model, new_field, new_type, new_collation):
+        return (
+            self.sql_alter_column_collate % {
+                'column': self.quote_name(new_field.column),
+                'type': new_type,
+                'collation': self._collate_sql(new_collation) if new_collation else '',
+            },
+            [],
+        )
+
     def _alter_many_to_many(self, model, old_field, new_field, strict):
         """Alter M2Ms to repoint their to= endpoints."""
         # Rename the through table
@@ -1274,6 +1296,9 @@ class BaseDatabaseSchemaEditor:
     def _delete_primary_key_sql(self, model, name):
         return self._delete_constraint_sql(self.sql_delete_pk, model, name)
 
+    def _collate_sql(self, collation):
+        return ' COLLATE ' + self.quote_name(collation)
+
     def remove_procedure(self, procedure_name, param_types=()):
         sql = self.sql_delete_procedure % {
             'procedure': self.quote_name(procedure_name),
diff --git a/django/db/backends/mysql/features.py b/django/db/backends/mysql/features.py
index e97b3bfaa4..3713df549b 100644
--- a/django/db/backends/mysql/features.py
+++ b/django/db/backends/mysql/features.py
@@ -46,6 +46,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     order_by_nulls_first = True
     test_collations = {
         'ci': 'utf8_general_ci',
+        'non_default': 'utf8_esperanto_ci',
         'swedish_ci': 'utf8_swedish_ci',
     }
 
diff --git a/django/db/backends/mysql/introspection.py b/django/db/backends/mysql/introspection.py
index 1a104c7810..4c0178144a 100644
--- a/django/db/backends/mysql/introspection.py
+++ b/django/db/backends/mysql/introspection.py
@@ -10,7 +10,11 @@ from django.db.models import Index
 from django.utils.datastructures import OrderedSet
 
 FieldInfo = namedtuple('FieldInfo', BaseFieldInfo._fields + ('extra', 'is_unsigned', 'has_json_constraint'))
-InfoLine = namedtuple('InfoLine', 'col_name data_type max_len num_prec num_scale extra column_default is_unsigned')
+InfoLine = namedtuple(
+    'InfoLine',
+    'col_name data_type max_len num_prec num_scale extra column_default '
+    'collation is_unsigned'
+)
 
 
 class DatabaseIntrospection(BaseDatabaseIntrospection):
@@ -84,6 +88,15 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                     c.constraint_schema = DATABASE()
             """, [table_name])
             json_constraints = {row[0] for row in cursor.fetchall()}
+        # A default collation for the given table.
+        cursor.execute("""
+            SELECT  table_collation
+            FROM    information_schema.tables
+            WHERE   table_schema = DATABASE()
+            AND     table_name = %s
+        """, [table_name])
+        row = cursor.fetchone()
+        default_column_collation = row[0] if row else ''
         # information_schema database gives more accurate results for some figures:
         # - varchar length returned by cursor.description is an internal length,
         #   not visible length (#5725)
@@ -94,11 +107,16 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                 column_name, data_type, character_maximum_length,
                 numeric_precision, numeric_scale, extra, column_default,
                 CASE
+                    WHEN collation_name = %s THEN NULL
+                    ELSE collation_name
+                END AS collation_name,
+                CASE
                     WHEN column_type LIKE '%% unsigned' THEN 1
                     ELSE 0
                 END AS is_unsigned
             FROM information_schema.columns
-            WHERE table_name = %s AND table_schema = DATABASE()""", [table_name])
+            WHERE table_name = %s AND table_schema = DATABASE()
+        """, [default_column_collation, table_name])
         field_info = {line[0]: InfoLine(*line) for line in cursor.fetchall()}
 
         cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
@@ -116,6 +134,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                 to_int(info.num_scale) or line[5],
                 line[6],
                 info.column_default,
+                info.collation,
                 info.extra,
                 info.is_unsigned,
                 line[0] in json_constraints,
diff --git a/django/db/backends/mysql/schema.py b/django/db/backends/mysql/schema.py
index 71b021f7c5..728f2f6c64 100644
--- a/django/db/backends/mysql/schema.py
+++ b/django/db/backends/mysql/schema.py
@@ -9,6 +9,7 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     sql_alter_column_null = "MODIFY %(column)s %(type)s NULL"
     sql_alter_column_not_null = "MODIFY %(column)s %(type)s NOT NULL"
     sql_alter_column_type = "MODIFY %(column)s %(type)s"
+    sql_alter_column_collate = "MODIFY %(column)s %(type)s%(collation)s"
 
     # No 'CASCADE' which works as a no-op in MySQL but is undocumented
     sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
diff --git a/django/db/backends/oracle/features.py b/django/db/backends/oracle/features.py
index 88739f5221..b0eebe5008 100644
--- a/django/db/backends/oracle/features.py
+++ b/django/db/backends/oracle/features.py
@@ -1,4 +1,4 @@
-from django.db import InterfaceError
+from django.db import DatabaseError, InterfaceError
 from django.db.backends.base.features import BaseDatabaseFeatures
 from django.utils.functional import cached_property
 
@@ -61,9 +61,11 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_boolean_expr_in_select_clause = False
     supports_primitives_in_json_field = False
     supports_json_field_contains = False
+    supports_collation_on_textfield = False
     test_collations = {
         'ci': 'BINARY_CI',
         'cs': 'BINARY',
+        'non_default': 'SWEDISH_CI',
         'swedish_ci': 'SWEDISH_CI',
     }
 
@@ -78,3 +80,14 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             'SmallIntegerField': 'IntegerField',
             'TimeField': 'DateTimeField',
         }
+
+    @cached_property
+    def supports_collation_on_charfield(self):
+        with self.connection.cursor() as cursor:
+            try:
+                cursor.execute("SELECT CAST('a' AS VARCHAR2(4001)) FROM dual")
+            except DatabaseError as e:
+                if e.args[0].code == 910:
+                    return False
+                raise
+            return True
diff --git a/django/db/backends/oracle/introspection.py b/django/db/backends/oracle/introspection.py
index 41ffb68afb..a5df7f1297 100644
--- a/django/db/backends/oracle/introspection.py
+++ b/django/db/backends/oracle/introspection.py
@@ -95,14 +95,20 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         # user_tab_columns gives data default for columns
         cursor.execute("""
             SELECT
-                column_name,
-                data_default,
+                user_tab_cols.column_name,
+                user_tab_cols.data_default,
                 CASE
-                    WHEN char_used IS NULL THEN data_length
-                    ELSE char_length
+                    WHEN user_tab_cols.collation = user_tables.default_collation
+                    THEN NULL
+                    ELSE user_tab_cols.collation
+                END collation,
+                CASE
+                    WHEN user_tab_cols.char_used IS NULL
+                    THEN user_tab_cols.data_length
+                    ELSE user_tab_cols.char_length
                 END as internal_size,
                 CASE
-                    WHEN identity_column = 'YES' THEN 1
+                    WHEN user_tab_cols.identity_column = 'YES' THEN 1
                     ELSE 0
                 END as is_autofield,
                 CASE
@@ -117,10 +123,13 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                     ELSE 0
                 END as is_json
             FROM user_tab_cols
-            WHERE table_name = UPPER(%s)""", [table_name])
+            LEFT OUTER JOIN
+                user_tables ON user_tables.table_name = user_tab_cols.table_name
+            WHERE user_tab_cols.table_name = UPPER(%s)
+        """, [table_name])
         field_map = {
-            column: (internal_size, default if default != 'NULL' else None, is_autofield, is_json)
-            for column, default, internal_size, is_autofield, is_json in cursor.fetchall()
+            column: (internal_size, default if default != 'NULL' else None, collation, is_autofield, is_json)
+            for column, default, collation, internal_size, is_autofield, is_json in cursor.fetchall()
         }
         self.cache_bust_counter += 1
         cursor.execute("SELECT * FROM {} WHERE ROWNUM < 2 AND {} > 0".format(
@@ -129,11 +138,11 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         description = []
         for desc in cursor.description:
             name = desc[0]
-            internal_size, default, is_autofield, is_json = field_map[name]
+            internal_size, default, collation, is_autofield, is_json = field_map[name]
             name = name % {}  # cx_Oracle, for some reason, doubles percent signs.
             description.append(FieldInfo(
                 self.identifier_converter(name), *desc[1:3], internal_size, desc[4] or 0,
-                desc[5] or 0, *desc[6:], default, is_autofield, is_json,
+                desc[5] or 0, *desc[6:], default, collation, is_autofield, is_json,
             ))
         return description
 
diff --git a/django/db/backends/oracle/schema.py b/django/db/backends/oracle/schema.py
index 002cb9e48b..3197fcc892 100644
--- a/django/db/backends/oracle/schema.py
+++ b/django/db/backends/oracle/schema.py
@@ -14,6 +14,8 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     sql_alter_column_not_null = "MODIFY %(column)s NOT NULL"
     sql_alter_column_default = "MODIFY %(column)s DEFAULT %(default)s"
     sql_alter_column_no_default = "MODIFY %(column)s DEFAULT NULL"
+    sql_alter_column_collate = "MODIFY %(column)s %(type)s%(collation)s"
+
     sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
     sql_create_column_inline_fk = 'CONSTRAINT %(name)s REFERENCES %(to_table)s(%(to_column)s)%(deferrable)s'
     sql_delete_table = "DROP TABLE %(table)s CASCADE CONSTRAINTS"
@@ -181,3 +183,15 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
             'table': self.quote_name(table_name),
             'column': self.quote_name(column_name),
         })
+
+    def _get_default_collation(self, table_name):
+        with self.connection.cursor() as cursor:
+            cursor.execute("""
+                SELECT default_collation FROM user_tables WHERE table_name = %s
+            """, [self.normalize_name(table_name)])
+            return cursor.fetchone()[0]
+
+    def _alter_column_collation_sql(self, model, new_field, new_type, new_collation):
+        if new_collation is None:
+            new_collation = self._get_default_collation(model._meta.db_table)
+        return super()._alter_column_collation_sql(model, new_field, new_type, new_collation)
diff --git a/django/db/backends/postgresql/features.py b/django/db/backends/postgresql/features.py
index 9080e75a36..e70ef4e95d 100644
--- a/django/db/backends/postgresql/features.py
+++ b/django/db/backends/postgresql/features.py
@@ -59,6 +59,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     has_json_operators = True
     json_key_contains_list_matching_requires_list = True
     test_collations = {
+        'non_default': 'sv-x-icu',
         'swedish_ci': 'sv-x-icu',
     }
 
@@ -92,3 +93,4 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_table_partitions = property(operator.attrgetter('is_postgresql_10'))
     supports_covering_indexes = property(operator.attrgetter('is_postgresql_11'))
     supports_covering_gist_indexes = property(operator.attrgetter('is_postgresql_12'))
+    supports_non_deterministic_collations = property(operator.attrgetter('is_postgresql_12'))
diff --git a/django/db/backends/postgresql/introspection.py b/django/db/backends/postgresql/introspection.py
index b7952eaed7..a0e49c8da7 100644
--- a/django/db/backends/postgresql/introspection.py
+++ b/django/db/backends/postgresql/introspection.py
@@ -69,9 +69,11 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
             SELECT
                 a.attname AS column_name,
                 NOT (a.attnotnull OR (t.typtype = 'd' AND t.typnotnull)) AS is_nullable,
-                pg_get_expr(ad.adbin, ad.adrelid) AS column_default
+                pg_get_expr(ad.adbin, ad.adrelid) AS column_default,
+                CASE WHEN collname = 'default' THEN NULL ELSE collname END AS collation
             FROM pg_attribute a
             LEFT JOIN pg_attrdef ad ON a.attrelid = ad.adrelid AND a.attnum = ad.adnum
+            LEFT JOIN pg_collation co ON a.attcollation = co.oid
             JOIN pg_type t ON a.atttypid = t.oid
             JOIN pg_class c ON a.attrelid = c.oid
             JOIN pg_namespace n ON c.relnamespace = n.oid
diff --git a/django/db/backends/sqlite3/features.py b/django/db/backends/sqlite3/features.py
index e879e049f9..59b8d6862f 100644
--- a/django/db/backends/sqlite3/features.py
+++ b/django/db/backends/sqlite3/features.py
@@ -47,6 +47,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     test_collations = {
         'ci': 'nocase',
         'cs': 'binary',
+        'non_default': 'nocase',
     }
 
     @cached_property
diff --git a/django/db/backends/sqlite3/introspection.py b/django/db/backends/sqlite3/introspection.py
index 3cbf844559..1d7ce3fabf 100644
--- a/django/db/backends/sqlite3/introspection.py
+++ b/django/db/backends/sqlite3/introspection.py
@@ -84,6 +84,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         """
         cursor.execute('PRAGMA table_info(%s)' % self.connection.ops.quote_name(table_name))
         table_info = cursor.fetchall()
+        collations = self._get_column_collations(cursor, table_name)
         json_columns = set()
         if self.connection.features.can_introspect_json_field:
             for line in table_info:
@@ -102,7 +103,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         return [
             FieldInfo(
                 name, data_type, None, get_field_size(data_type), None, None,
-                not notnull, default, pk == 1, name in json_columns
+                not notnull, default, collations.get(name), pk == 1, name in json_columns
             )
             for cid, name, data_type, notnull, default, pk in table_info
         ]
@@ -435,3 +436,27 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
             }
         constraints.update(self._get_foreign_key_constraints(cursor, table_name))
         return constraints
+
+    def _get_column_collations(self, cursor, table_name):
+        row = cursor.execute("""
+            SELECT sql
+            FROM sqlite_master
+            WHERE type = 'table' AND name = %s
+        """, [table_name]).fetchone()
+        if not row:
+            return {}
+
+        sql = row[0]
+        columns = str(sqlparse.parse(sql)[0][-1]).strip('()').split(', ')
+        collations = {}
+        for column in columns:
+            tokens = column[1:].split()
+            column_name = tokens[0].strip('"')
+            for index, token in enumerate(tokens):
+                if token == 'COLLATE':
+                    collation = tokens[index + 1]
+                    break
+            else:
+                collation = None
+            collations[column_name] = collation
+        return collations
diff --git a/django/db/backends/sqlite3/schema.py b/django/db/backends/sqlite3/schema.py
index 146ad18f84..6a2c887612 100644
--- a/django/db/backends/sqlite3/schema.py
+++ b/django/db/backends/sqlite3/schema.py
@@ -429,3 +429,6 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
             super().remove_constraint(model, constraint)
         else:
             self._remake_table(model)
+
+    def _collate_sql(self, collation):
+        return ' COLLATE ' + collation
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 15e69d3704..2bce85beef 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1002,13 +1002,16 @@ class BooleanField(Field):
 class CharField(Field):
     description = _("String (up to %(max_length)s)")
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args, db_collation=None, **kwargs):
         super().__init__(*args, **kwargs)
+        self.db_collation = db_collation
         self.validators.append(validators.MaxLengthValidator(self.max_length))
 
     def check(self, **kwargs):
+        databases = kwargs.get('databases') or []
         return [
             *super().check(**kwargs),
+            *self._check_db_collation(databases),
             *self._check_max_length_attribute(**kwargs),
         ]
 
@@ -1033,6 +1036,27 @@ class CharField(Field):
         else:
             return []
 
+    def _check_db_collation(self, databases):
+        errors = []
+        for db in databases:
+            if not router.allow_migrate_model(db, self.model):
+                continue
+            connection = connections[db]
+            if not (
+                self.db_collation is None or
+                'supports_collation_on_charfield' in self.model._meta.required_db_features or
+                connection.features.supports_collation_on_charfield
+            ):
+                errors.append(
+                    checks.Error(
+                        '%s does not support a database collation on '
+                        'CharFields.' % connection.display_name,
+                        obj=self,
+                        id='fields.E190',
+                    ),
+                )
+        return errors
+
     def cast_db_type(self, connection):
         if self.max_length is None:
             return connection.ops.cast_char_field_without_max_length
@@ -1061,6 +1085,12 @@ class CharField(Field):
         defaults.update(kwargs)
         return super().formfield(**defaults)
 
+    def deconstruct(self):
+        name, path, args, kwargs = super().deconstruct()
+        if self.db_collation:
+            kwargs['db_collation'] = self.db_collation
+        return name, path, args, kwargs
+
 
 class CommaSeparatedIntegerField(CharField):
     default_validators = [validators.validate_comma_separated_integer_list]
@@ -2074,6 +2104,38 @@ class SmallIntegerField(IntegerField):
 class TextField(Field):
     description = _("Text")
 
+    def __init__(self, *args, db_collation=None, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.db_collation = db_collation
+
+    def check(self, **kwargs):
+        databases = kwargs.get('databases') or []
+        return [
+            *super().check(**kwargs),
+            *self._check_db_collation(databases),
+        ]
+
+    def _check_db_collation(self, databases):
+        errors = []
+        for db in databases:
+            if not router.allow_migrate_model(db, self.model):
+                continue
+            connection = connections[db]
+            if not (
+                self.db_collation is None or
+                'supports_collation_on_textfield' in self.model._meta.required_db_features or
+                connection.features.supports_collation_on_textfield
+            ):
+                errors.append(
+                    checks.Error(
+                        '%s does not support a database collation on '
+                        'TextFields.' % connection.display_name,
+                        obj=self,
+                        id='fields.E190',
+                    ),
+                )
+        return errors
+
     def get_internal_type(self):
         return "TextField"
 
@@ -2096,6 +2158,12 @@ class TextField(Field):
             **kwargs,
         })
 
+    def deconstruct(self):
+        name, path, args, kwargs = super().deconstruct()
+        if self.db_collation:
+            kwargs['db_collation'] = self.db_collation
+        return name, path, args, kwargs
+
 
 class TimeField(DateTimeCheckMixin, Field):
     empty_strings_allowed = False
diff --git a/docs/ref/checks.txt b/docs/ref/checks.txt
index 0e1ee50b46..ffb629f96c 100644
--- a/docs/ref/checks.txt
+++ b/docs/ref/checks.txt
@@ -196,6 +196,8 @@ Model fields
 * **fields.E170**: ``BinaryField``’s ``default`` cannot be a string. Use bytes
   content instead.
 * **fields.E180**: ``<database>`` does not support ``JSONField``\s.
+* **fields.E190**: ``<database>`` does not support a database collation on
+  ``<field_type>``\s.
 * **fields.E900**: ``IPAddressField`` has been removed except for support in
   historical migrations.
 * **fields.W900**: ``IPAddressField`` has been deprecated. Support for it
diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt
index fd7e88d168..93c011fe2c 100644
--- a/docs/ref/models/fields.txt
+++ b/docs/ref/models/fields.txt
@@ -593,20 +593,36 @@ For large amounts of text, use :class:`~django.db.models.TextField`.
 
 The default form widget for this field is a :class:`~django.forms.TextInput`.
 
-:class:`CharField` has one extra required argument:
+:class:`CharField` has two extra arguments:
 
 .. attribute:: CharField.max_length
 
-    The maximum length (in characters) of the field. The max_length is enforced
-    at the database level and in Django's validation using
+    Required. The maximum length (in characters) of the field. The max_length
+    is enforced at the database level and in Django's validation using
     :class:`~django.core.validators.MaxLengthValidator`.
 
-.. note::
+    .. note::
+
+        If you are writing an application that must be portable to multiple
+        database backends, you should be aware that there are restrictions on
+        ``max_length`` for some backends. Refer to the :doc:`database backend
+        notes </ref/databases>` for details.
+
+.. attribute:: CharField.db_collation
+
+    .. versionadded:: 3.2
+
+    Optional. The database collation name of the field.
+
+    .. note::
+
+        Collation names are not standardized. As such, this will not be
+        portable across multiple database backends.
 
-    If you are writing an application that must be portable to multiple
-    database backends, you should be aware that there are restrictions on
-    ``max_length`` for some backends. Refer to the :doc:`database backend
-    notes </ref/databases>` for details.
+    .. admonition:: Oracle
+
+        Oracle supports collations only when the ``MAX_STRING_SIZE`` database
+        initialization parameter is set to ``EXTENDED``.
 
 ``DateField``
 -------------
@@ -1329,6 +1345,21 @@ If you specify a ``max_length`` attribute, it will be reflected in the
 However it is not enforced at the model or database level. Use a
 :class:`CharField` for that.
 
+.. attribute:: TextField.db_collation
+
+    .. versionadded:: 3.2
+
+    The database collation name of the field.
+
+    .. note::
+
+        Collation names are not standardized. As such, this will not be
+        portable across multiple database backends.
+
+    .. admonition:: Oracle
+
+        Oracle does not support collations for a ``TextField``.
+
 ``TimeField``
 -------------
 
diff --git a/docs/releases/3.2.txt b/docs/releases/3.2.txt
index e66e5777d5..2c59c488c0 100644
--- a/docs/releases/3.2.txt
+++ b/docs/releases/3.2.txt
@@ -308,6 +308,11 @@ Models
   :class:`~django.db.models.functions.TruncTime` database functions allows
   truncating datetimes in a specific timezone.
 
+* The new ``db_collation`` argument for
+  :attr:`CharField <django.db.models.CharField.db_collation>` and
+  :attr:`TextField <django.db.models.TextField.db_collation>` allows setting a
+  database collation for the field.
+
 Pagination
 ~~~~~~~~~~
 
@@ -431,6 +436,13 @@ backends.
   unique constraints (:attr:`.UniqueConstraint.include`), set
   ``DatabaseFeatures.supports_covering_indexes`` to ``True``.
 
+* Third-party database backends must implement support for column database
+  collations on ``CharField``\s and ``TextField``\s or set
+  ``DatabaseFeatures.supports_collation_on_charfield`` and
+  ``DatabaseFeatures.supports_collation_on_textfield`` to ``False``. If
+  non-deterministic collations are not supported, set
+  ``supports_non_deterministic_collations`` to ``False``.
+
 :mod:`django.contrib.admin`
 ---------------------------
 
diff --git a/tests/inspectdb/models.py b/tests/inspectdb/models.py
index d0076ce94f..4d2c224da9 100644
--- a/tests/inspectdb/models.py
+++ b/tests/inspectdb/models.py
@@ -1,4 +1,4 @@
-from django.db import models
+from django.db import connection, models
 
 
 class People(models.Model):
@@ -79,6 +79,23 @@ class JSONFieldColumnType(models.Model):
         }
 
 
+test_collation = connection.features.test_collations.get('non_default')
+
+
+class CharFieldDbCollation(models.Model):
+    char_field = models.CharField(max_length=10, db_collation=test_collation)
+
+    class Meta:
+        required_db_features = {'supports_collation_on_charfield'}
+
+
+class TextFieldDbCollation(models.Model):
+    text_field = models.TextField(db_collation=test_collation)
+
+    class Meta:
+        required_db_features = {'supports_collation_on_textfield'}
+
+
 class UniqueTogether(models.Model):
     field1 = models.IntegerField()
     field2 = models.CharField(max_length=10)
diff --git a/tests/inspectdb/tests.py b/tests/inspectdb/tests.py
index fa3a7ac21f..6815629e95 100644
--- a/tests/inspectdb/tests.py
+++ b/tests/inspectdb/tests.py
@@ -8,7 +8,7 @@ from django.db import connection
 from django.db.backends.base.introspection import TableInfo
 from django.test import TestCase, TransactionTestCase, skipUnlessDBFeature
 
-from .models import PeopleMoreData
+from .models import PeopleMoreData, test_collation
 
 
 def inspectdb_tables_only(table_name):
@@ -104,6 +104,41 @@ class InspectDBTestCase(TestCase):
             self.assertIn('json_field = models.JSONField()', output)
         self.assertIn('null_json_field = models.JSONField(blank=True, null=True)', output)
 
+    @skipUnlessDBFeature('supports_collation_on_charfield')
+    def test_char_field_db_collation(self):
+        out = StringIO()
+        call_command('inspectdb', 'inspectdb_charfielddbcollation', stdout=out)
+        output = out.getvalue()
+        if not connection.features.interprets_empty_strings_as_nulls:
+            self.assertIn(
+                "char_field = models.CharField(max_length=10, "
+                "db_collation='%s')" % test_collation,
+                output,
+            )
+        else:
+            self.assertIn(
+                "char_field = models.CharField(max_length=10, "
+                "db_collation='%s', blank=True, null=True)" % test_collation,
+                output,
+            )
+
+    @skipUnlessDBFeature('supports_collation_on_textfield')
+    def test_text_field_db_collation(self):
+        out = StringIO()
+        call_command('inspectdb', 'inspectdb_textfielddbcollation', stdout=out)
+        output = out.getvalue()
+        if not connection.features.interprets_empty_strings_as_nulls:
+            self.assertIn(
+                "text_field = models.TextField(db_collation='%s')" % test_collation,
+                output,
+            )
+        else:
+            self.assertIn(
+                "text_field = models.TextField(db_collation='%s, blank=True, "
+                "null=True)" % test_collation,
+                output,
+            )
+
     def test_number_field_types(self):
         """Test introspection of various Django field types"""
         assertFieldType = self.make_field_type_asserter()
diff --git a/tests/invalid_models_tests/test_ordinary_fields.py b/tests/invalid_models_tests/test_ordinary_fields.py
index a81f9eed90..6eddd853af 100644
--- a/tests/invalid_models_tests/test_ordinary_fields.py
+++ b/tests/invalid_models_tests/test_ordinary_fields.py
@@ -86,7 +86,7 @@ class BinaryFieldTests(SimpleTestCase):
 
 
 @isolate_apps('invalid_models_tests')
-class CharFieldTests(SimpleTestCase):
+class CharFieldTests(TestCase):
 
     def test_valid_field(self):
         class Model(models.Model):
@@ -387,6 +387,30 @@ class CharFieldTests(SimpleTestCase):
             )
         ])
 
+    def test_db_collation(self):
+        class Model(models.Model):
+            field = models.CharField(max_length=100, db_collation='anything')
+
+        field = Model._meta.get_field('field')
+        error = Error(
+            '%s does not support a database collation on CharFields.'
+            % connection.display_name,
+            id='fields.E190',
+            obj=field,
+        )
+        expected = [] if connection.features.supports_collation_on_charfield else [error]
+        self.assertEqual(field.check(databases=self.databases), expected)
+
+    def test_db_collation_required_db_features(self):
+        class Model(models.Model):
+            field = models.CharField(max_length=100, db_collation='anything')
+
+            class Meta:
+                required_db_features = {'supports_collation_on_charfield'}
+
+        field = Model._meta.get_field('field')
+        self.assertEqual(field.check(databases=self.databases), [])
+
 
 @isolate_apps('invalid_models_tests')
 class DateFieldTests(SimpleTestCase):
@@ -779,6 +803,30 @@ class TextFieldTests(TestCase):
             )
         ])
 
+    def test_db_collation(self):
+        class Model(models.Model):
+            field = models.TextField(db_collation='anything')
+
+        field = Model._meta.get_field('field')
+        error = Error(
+            '%s does not support a database collation on TextFields.'
+            % connection.display_name,
+            id='fields.E190',
+            obj=field,
+        )
+        expected = [] if connection.features.supports_collation_on_textfield else [error]
+        self.assertEqual(field.check(databases=self.databases), expected)
+
+    def test_db_collation_required_db_features(self):
+        class Model(models.Model):
+            field = models.TextField(db_collation='anything')
+
+            class Meta:
+                required_db_features = {'supports_collation_on_textfield'}
+
+        field = Model._meta.get_field('field')
+        self.assertEqual(field.check(databases=self.databases), [])
+
 
 @isolate_apps('invalid_models_tests')
 class UUIDFieldTests(TestCase):
diff --git a/tests/model_fields/test_charfield.py b/tests/model_fields/test_charfield.py
index cf3ce0c4c5..a8ac895a11 100644
--- a/tests/model_fields/test_charfield.py
+++ b/tests/model_fields/test_charfield.py
@@ -44,6 +44,16 @@ class TestCharField(TestCase):
         self.assertEqual(p2.title, Event.C)
 
 
+class TestMethods(SimpleTestCase):
+    def test_deconstruct(self):
+        field = models.CharField()
+        *_, kwargs = field.deconstruct()
+        self.assertEqual(kwargs, {})
+        field = models.CharField(db_collation='utf8_esperanto_ci')
+        *_, kwargs = field.deconstruct()
+        self.assertEqual(kwargs, {'db_collation': 'utf8_esperanto_ci'})
+
+
 class ValidationTests(SimpleTestCase):
 
     class Choices(models.TextChoices):
diff --git a/tests/model_fields/test_textfield.py b/tests/model_fields/test_textfield.py
index 82e7af8fd5..f0bce822a4 100644
--- a/tests/model_fields/test_textfield.py
+++ b/tests/model_fields/test_textfield.py
@@ -2,7 +2,7 @@ from unittest import skipIf
 
 from django import forms
 from django.db import connection, models
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 
 from .models import Post
 
@@ -37,3 +37,13 @@ class TextFieldTests(TestCase):
         p = Post.objects.create(title='Whatever', body='Smile 😀.')
         p.refresh_from_db()
         self.assertEqual(p.body, 'Smile 😀.')
+
+
+class TestMethods(SimpleTestCase):
+    def test_deconstruct(self):
+        field = models.TextField()
+        *_, kwargs = field.deconstruct()
+        self.assertEqual(kwargs, {})
+        field = models.TextField(db_collation='utf8_esperanto_ci')
+        *_, kwargs = field.deconstruct()
+        self.assertEqual(kwargs, {'db_collation': 'utf8_esperanto_ci'})
diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index 8e992b4917..396d7c7c4f 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -185,6 +185,14 @@ class SchemaTests(TransactionTestCase):
                     counts['indexes'] += 1
         return counts
 
+    def get_column_collation(self, table, column):
+        with connection.cursor() as cursor:
+            return next(
+                f.collation
+                for f in connection.introspection.get_table_description(cursor, table)
+                if f.name == column
+            )
+
     def assertIndexOrder(self, table, index, order):
         constraints = self.get_constraints(table)
         self.assertIn(index, constraints)
@@ -3224,3 +3232,147 @@ class SchemaTests(TransactionTestCase):
         with connection.schema_editor(atomic=True) as editor:
             editor.alter_db_table(Foo, Foo._meta.db_table, 'renamed_table')
         Foo._meta.db_table = 'renamed_table'
+
+    @isolate_apps('schema')
+    @skipUnlessDBFeature('supports_collation_on_charfield')
+    def test_db_collation_charfield(self):
+        collation = connection.features.test_collations['non_default']
+
+        class Foo(Model):
+            field = CharField(max_length=255, db_collation=collation)
+
+            class Meta:
+                app_label = 'schema'
+
+        self.isolated_local_models = [Foo]
+        with connection.schema_editor() as editor:
+            editor.create_model(Foo)
+
+        self.assertEqual(
+            self.get_column_collation(Foo._meta.db_table, 'field'),
+            collation,
+        )
+
+    @isolate_apps('schema')
+    @skipUnlessDBFeature('supports_collation_on_textfield')
+    def test_db_collation_textfield(self):
+        collation = connection.features.test_collations['non_default']
+
+        class Foo(Model):
+            field = TextField(db_collation=collation)
+
+            class Meta:
+                app_label = 'schema'
+
+        self.isolated_local_models = [Foo]
+        with connection.schema_editor() as editor:
+            editor.create_model(Foo)
+
+        self.assertEqual(
+            self.get_column_collation(Foo._meta.db_table, 'field'),
+            collation,
+        )
+
+    @skipUnlessDBFeature('supports_collation_on_charfield')
+    def test_add_field_db_collation(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+
+        collation = connection.features.test_collations['non_default']
+        new_field = CharField(max_length=255, db_collation=collation)
+        new_field.set_attributes_from_name('alias')
+        with connection.schema_editor() as editor:
+            editor.add_field(Author, new_field)
+        columns = self.column_classes(Author)
+        self.assertEqual(
+            columns['alias'][0],
+            connection.features.introspected_field_types['CharField'],
+        )
+        self.assertEqual(columns['alias'][1][8], collation)
+
+    @skipUnlessDBFeature('supports_collation_on_charfield')
+    def test_alter_field_db_collation(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+
+        collation = connection.features.test_collations['non_default']
+        old_field = Author._meta.get_field('name')
+        new_field = CharField(max_length=255, db_collation=collation)
+        new_field.set_attributes_from_name('name')
+        new_field.model = Author
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, old_field, new_field, strict=True)
+        self.assertEqual(
+            self.get_column_collation(Author._meta.db_table, 'name'),
+            collation,
+        )
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, new_field, old_field, strict=True)
+        self.assertIsNone(self.get_column_collation(Author._meta.db_table, 'name'))
+
+    @skipUnlessDBFeature('supports_collation_on_charfield')
+    def test_alter_field_type_and_db_collation(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Note)
+
+        collation = connection.features.test_collations['non_default']
+        old_field = Note._meta.get_field('info')
+        new_field = CharField(max_length=255, db_collation=collation)
+        new_field.set_attributes_from_name('info')
+        new_field.model = Note
+        with connection.schema_editor() as editor:
+            editor.alter_field(Note, old_field, new_field, strict=True)
+        columns = self.column_classes(Note)
+        self.assertEqual(
+            columns['info'][0],
+            connection.features.introspected_field_types['CharField'],
+        )
+        self.assertEqual(columns['info'][1][8], collation)
+        with connection.schema_editor() as editor:
+            editor.alter_field(Note, new_field, old_field, strict=True)
+        columns = self.column_classes(Note)
+        self.assertEqual(columns['info'][0], 'TextField')
+        self.assertIsNone(columns['info'][1][8])
+
+    @skipUnlessDBFeature(
+        'supports_collation_on_charfield',
+        'supports_non_deterministic_collations',
+    )
+    def test_ci_cs_db_collation(self):
+        cs_collation = connection.features.test_collations.get('cs')
+        ci_collation = connection.features.test_collations.get('ci')
+        try:
+            if connection.vendor == 'mysql':
+                cs_collation = 'latin1_general_cs'
+            elif connection.vendor == 'postgresql':
+                cs_collation = 'en-x-icu'
+                with connection.cursor() as cursor:
+                    cursor.execute(
+                        "CREATE COLLATION IF NOT EXISTS case_insensitive "
+                        "(provider = icu, locale = 'und-u-ks-level2', "
+                        "deterministic = false)"
+                    )
+                    ci_collation = 'case_insensitive'
+            # Create the table.
+            with connection.schema_editor() as editor:
+                editor.create_model(Author)
+            # Case-insensitive collation.
+            old_field = Author._meta.get_field('name')
+            new_field_ci = CharField(max_length=255, db_collation=ci_collation)
+            new_field_ci.set_attributes_from_name('name')
+            new_field_ci.model = Author
+            with connection.schema_editor() as editor:
+                editor.alter_field(Author, old_field, new_field_ci, strict=True)
+            Author.objects.create(name='ANDREW')
+            self.assertIs(Author.objects.filter(name='Andrew').exists(), True)
+            # Case-sensitive collation.
+            new_field_cs = CharField(max_length=255, db_collation=cs_collation)
+            new_field_cs.set_attributes_from_name('name')
+            new_field_cs.model = Author
+            with connection.schema_editor() as editor:
+                editor.alter_field(Author, new_field_ci, new_field_cs, strict=True)
+            self.assertIs(Author.objects.filter(name='Andrew').exists(), False)
+        finally:
+            if connection.vendor == 'postgresql':
+                with connection.cursor() as cursor:
+                    cursor.execute('DROP COLLATION IF EXISTS case_insensitive')