add rename_schema method for postgres

Author: tsvallender

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Add `rename_schema` method for PostgreSQL.
+
+    *T S Vallender*
+
 *   Implement support for deprecating associations:
 
     ```ruby

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -279,6 +279,11 @@ def drop_schema(schema_name, **options)
           execute "DROP SCHEMA#{' IF EXISTS' if options[:if_exists]} #{quote_schema_name(schema_name)} CASCADE"
         end
 
+        # Renames the schema for the given schema name.
+        def rename_schema(schema_name, new_name)
+          execute "ALTER SCHEMA #{quote_schema_name(schema_name)} RENAME TO #{quote_schema_name(new_name)}"
+        end
+
         # Sets the schema search path to a string of comma-separated schema names.
         # Names beginning with $ have to be quoted (e.g. $user => '$user').
         # See: https://www.postgresql.org/docs/current/static/ddl-schemas.html

activerecord/test/cases/adapters/postgresql/schema_test.rb

@@ -201,6 +201,33 @@ def test_drop_schema_with_nonexisting_schema
     end
   end
 
+  def test_rename_schema
+    @connection.create_schema("test_schema3")
+    @connection.rename_schema("test_schema3", "test_schema4")
+    assert_not_includes @connection.schema_names, "test_schema3"
+    assert_includes @connection.schema_names, "test_schema4"
+  ensure
+    @connection.drop_schema("test_schema3", if_exists: true)
+    @connection.drop_schema("test_schema4", if_exists: true)
+  end
+
+  def test_rename_schema_with_nonexisting_schema
+    assert_raises(ActiveRecord::StatementInvalid) do
+      @connection.rename_schema("idontexist", "neitherdoi")
+    end
+  end
+
+  def test_rename_schema_with_existing_target_name
+    @connection.create_schema("test_schema3")
+    @connection.create_schema("test_schema4")
+    assert_raises(ActiveRecord::StatementInvalid) do
+      @connection.rename_schema("test_schema3", "test_schema4")
+    end
+  ensure
+    @connection.drop_schema("test_schema3", if_exists: true)
+    @connection.drop_schema("test_schema4", if_exists: true)
+  end
+
   def test_raise_wrapped_exception_on_bad_prepare
     assert_raises(ActiveRecord::StatementInvalid) do
       @connection.exec_query "select * from developers where id = ?", "sql", [bind_param(1)]