[1.7.x] Fixed #23065 -- Quoted constraint names in SQL generated by migrations.

Backport of 83cd18633f from master

django/db/backends/schema.py

@@ -646,7 +646,7 @@ class BaseDatabaseSchemaEditor(object):
             self.execute(
                 self.sql_create_pk % {
                     "table": self.quote_name(model._meta.db_table),
-                    "name": self._create_index_name(model, [new_field.column], suffix="_pk"),
+                    "name": self.quote_name(self._create_index_name(model, [new_field.column], suffix="_pk")),
                     "columns": self.quote_name(new_field.column),
                 }
             )
@@ -679,7 +679,7 @@ class BaseDatabaseSchemaEditor(object):
             self.execute(
                 self.sql_create_check % {
                     "table": self.quote_name(model._meta.db_table),
-                    "name": self._create_index_name(model, [new_field.column], suffix="_check"),
+                    "name": self.quote_name(self._create_index_name(model, [new_field.column], suffix="_check")),
                     "column": self.quote_name(new_field.column),
                     "check": new_db_params['check'],
                 }
@@ -769,7 +769,7 @@ class BaseDatabaseSchemaEditor(object):
         columns = [field.column for field in fields]
         return self.sql_create_index % {
             "table": self.quote_name(model._meta.db_table),
-            "name": self._create_index_name(model, columns, suffix=suffix),
+            "name": self.quote_name(self._create_index_name(model, columns, suffix=suffix)),
             "columns": ", ".join(self.quote_name(column) for column in columns),
             "extra": "",
         }
@@ -786,7 +786,7 @@ class BaseDatabaseSchemaEditor(object):
 
         return self.sql_create_fk % {
             "table": self.quote_name(from_table),
-            "name": self._create_index_name(model, [from_column], suffix=suffix),
+            "name": self.quote_name(self._create_index_name(model, [from_column], suffix=suffix)),
             "column": self.quote_name(from_column),
             "to_table": self.quote_name(to_table),
             "to_column": self.quote_name(to_column),
@@ -795,14 +795,14 @@ class BaseDatabaseSchemaEditor(object):
     def _create_unique_sql(self, model, columns):
         return self.sql_create_unique % {
             "table": self.quote_name(model._meta.db_table),
-            "name": self._create_index_name(model, columns, suffix="_uniq"),
+            "name": self.quote_name(self._create_index_name(model, columns, suffix="_uniq")),
             "columns": ", ".join(self.quote_name(column) for column in columns),
         }
 
     def _delete_constraint_sql(self, template, model, name):
         return template % {
             "table": self.quote_name(model._meta.db_table),
-            "name": name,
+            "name": self.quote_name(name),
         }
 
     def _constraint_names(self, model, column_names=None, unique=None,

docs/releases/1.7.1.txt

@@ -55,3 +55,6 @@ Bugfixes
 * Formats for Welsh (``cy``) and several Chinese locales (``zh_CN``,
   ``zh_Hans``, ``zh_Hant`` and ``zh_TW``) have been added. Formats for
   Macedonian have been fixed (trailing dot removed, :ticket:`23532`).
+
+* Added quoting of constraint names in the SQL generated by migrations to
+  prevent crash with uppercase characters in the name (:ticket:`23065`).

tests/schema/tests.py

@@ -1040,3 +1040,53 @@ class SchemaTests(TransactionTestCase):
             DatabaseError,
             lambda: list(Thing.objects.all()),
         )
+
+    @unittest.skipUnless(connection.features.supports_foreign_keys, "No FK support")
+    def test_remove_constraints_capital_letters(self):
+        """
+        #23065 - Constraint names must be quoted if they contain capital letters.
+        """
+        def get_field(*args, **kwargs):
+            kwargs['db_column'] = "CamelCase"
+            field = kwargs.pop('field_class', IntegerField)(*args, **kwargs)
+            field.set_attributes_from_name("CamelCase")
+            return field
+
+        model = Author
+        field = get_field()
+        table = model._meta.db_table
+        column = field.column
+
+        with connection.schema_editor() as editor:
+            editor.create_model(model)
+            editor.add_field(model, field)
+
+            editor.execute(
+                editor.sql_create_index % {
+                    "table": editor.quote_name(table),
+                    "name": editor.quote_name("CamelCaseIndex"),
+                    "columns": editor.quote_name(column),
+                    "extra": "",
+                }
+            )
+            editor.alter_field(model, get_field(db_index=True), field)
+
+            editor.execute(
+                editor.sql_create_unique % {
+                    "table": editor.quote_name(table),
+                    "name": editor.quote_name("CamelCaseUniqConstraint"),
+                    "columns": editor.quote_name(field.column),
+                }
+            )
+            editor.alter_field(model, get_field(unique=True), field)
+
+            editor.execute(
+                editor.sql_create_fk % {
+                    "table": editor.quote_name(table),
+                    "name": editor.quote_name("CamelCaseFKConstraint"),
+                    "column": editor.quote_name(column),
+                    "to_table": editor.quote_name(table),
+                    "to_column": editor.quote_name(model._meta.auto_field.column),
+                }
+            )
+            editor.alter_field(model, get_field(Author, field_class=ForeignKey), field)