-function is_column(x) return getmetatable(x)==column_mt; end
-function is_index(x) return getmetatable(x)==index_mt; end
-function is_table(x) return getmetatable(x)==table_mt; end
-function is_query(x) return getmetatable(x)==query_mt; end
-function Integer(n) return "Integer()" end
-function String(n) return "String()" end
+local function is_column(x) return getmetatable(x)==column_mt; end
+local function is_index(x) return getmetatable(x)==index_mt; end
+local function is_table(x) return getmetatable(x)==table_mt; end
+local function is_query(x) return getmetatable(x)==query_mt; end
+local function Integer(n) return "Integer()" end
+local function String(n) return "String()" end