create type api_operation as enum ('init', 'add', 'delete', 'update');

create table operation
(
  id serial primary key
, redo text not null
, undo text not null
, parent integer references operation(id)
, redo_child integer references operation(id)
, api_id text not null
, api_op api_operation not null
, api_object_type text not null
, api_object_id text not null
, api_object_properties text[]
);

insert into operation (id, redo, undo, api_id, api_op, api_object_type, api_object_id) values (0, '', '', '', 'init', '', '');

create table current_operation
(
  id integer primary key references operation(id)
);

insert into current_operation (id) values (0);

create table snapshot_operation
(
  id integer primary key references operation(id)
, tag text not null unique
);

create table transaction_operation
(
  id integer primary key references operation(id)
, strict boolean not null default false
);