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(** Multigroup root: a lightweight versioned descriptor that maps relation names
to content-addressed relation values. The multigroup object owns the B+ tree
pointer and advances it when relations change. *)
class multigroup ~name:(init_name : Conventions.Name.t) =
object (_self)
val name : Conventions.Name.t = init_name
val relations : Relation.relation BatMap.String.t = BatMap.String.empty
val timestamp : float = Unix.gettimeofday ()
method name = name
method relations = relations
method timestamp = timestamp
(* TODO: a variant returning (Relation.relation, Condition.t) result *)
method get_relation rel_name = BatMap.String.find_opt rel_name relations
method get_relation_names = BatMap.String.fold (fun n _ acc -> n :: acc) relations []
method has_relation rel_name = BatMap.String.mem rel_name relations
method add_relation (rel : Relation.relation) =
{<relations = BatMap.String.add rel#name rel relations>}
method remove_relation rel_name = {<relations = BatMap.String.remove rel_name relations>}
method update_relation (rel : Relation.relation) =
if not (BatMap.String.mem rel#name relations) then {<>}
else {<relations = BatMap.String.add rel#name rel relations>}
method serialize () : Storable.Multigroup.t =
{ Storable.Multigroup.name;
relations=
BatMap.String.bindings relations |> List.map snd |> List.map (fun r -> r#serialize ()) }
end
let deserialize (bytes : bytes) : (multigroup, string) result =
(* Reconstruct a multigroup from its persisted payload.
Only name, schema, and tree_pointer (Merkle root) are restored per
relation. Constraints are not yet round-tripped — see the TODO in
storable.ml for the constraint serialisation plan. *)
try
let stored = Storable.Multigroup.of_bytes bytes in
let db = new multigroup ~name:stored.name in
let db =
List.fold_left
(fun mg rel ->
let relation =
new Relation.stored
~name:rel.Storable.Relation.name ~schema:rel.schema ~constraints:None
~cardinality:Conventions.Cardinality.AlephZero ~lineage:None ~provenance:None
~membership_criteria:(fun _ -> true )
in
let relation =
if rel.tree_pointer = "" then relation
else relation#set_tree_pointer (Some rel.tree_pointer)
in
mg#add_relation (relation :> Relation.relation) )
db stored.relations
in
Ok db
with Invalid_argument message -> Error message
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