1 files changed, 18 insertions, 0 deletions
diff --git a/lib/protocols/Relation.ml b/lib/protocols/Relation.ml
index 3962c9c..b4cc4ec 100644
--- a/lib/protocols/Relation.ml
+++ b/lib/protocols/Relation.ml
@@ -17,3 +17,21 @@ let make impl = Relation (impl :> implementation)
 let from handle = Handle.into handle (function Relation impl -> Some impl | _ -> None)
 let require handle = from handle |> Option.to_result ~none:(Error.not_a_relation ())
 let contains i tuple = Handle.invoke i (fun o -> o#contains tuple)
+
+let read relation =
+  let open Utilities.Result in
+  let* schematics = Handle.require Schematics.from relation in
+  let* description = Schematics.describe schematics in
+  let* heading =
+    match description with
+    | Schematics.Relation heading -> Ok heading
+    | _ -> Error (Error.not_a_relation ())
+  in
+  let* enumerable = Enumerable.require relation in
+  let* cursor = Enumerable.enumerate enumerable in
+  Fun.protect
+    ~finally:(fun () -> Handle.release cursor)
+    (fun () ->
+      let* scan = Cursor.require cursor in
+      let* tuples = Cursor.drain scan () in
+      Ok (heading, BatFingerTree.to_list tuples) )