query/todo.md

Todo

• move prepare_* methods from dialect to query_compiler

• add insert_query_builder and update_update_builder (returning multiple statements)

• finish fetch eager many-to-many relations

• implement lazy loading

• implement polymorphic class hierarchies

• finish database (schema_repository) class (move add/drop from session to schema)

• implement a flag class for enumerations

• PK generator

1. Introduce execute_context
2. Introduce execute_result
3. Add abstract_pk_generator class
4. Add identity_pk_generator class
5. Add sequence_pk_generator class
6. Add table_pk_generator class
7. Add manual_pk_generator class
8. Extend session::insert logic to use pk generator
9. Extend postgres_connection::execute to handle returning clause
10. Add generator to schema_node or table class when attaching type
11. Extend query_builder and intermediates with returning intermediate

Proposal for polymorphic classes:

object_ptr::as does the following checks;

1. The requested type has a super class
2. Super class has a discriminator column defined
3. Super class has a discriminator value defined
4. Discriminator value is mapped to the requested type

If all checks succeed, the requested is fetched from the database.

schema.attach<jobs::Payload>("payloads", make_polymorph("type"));
schema.attach<jobs::Payload, jobs::IdPayload>("id_list_payloads", make_polymorph_type("IdPayload"));
schema.attach<jobs::Payload, jobs::IdListPayload>("id_payloads", make_polymorph_type("IdListPayload"));
object::object_ptr<jobs::Payload> payload;
auto result = payload.as<jobs::IdPayload>();
if (result.is_ok()) {
  const auto& is_payload = result.value();
  // Use requested type
  id_payload->id = 1;
}
payload.is_polymorphic();
payload.is_polymorphic_type<jobs::IdPayload>();