LMDB Storage: add batch remove

Author: glyh

src/lib/lmdb_storage/generic.ml

@@ -237,4 +237,8 @@ module Read_write (F_func : F) = struct
 
   let remove ~env:t db key =
     with_env t ~perm:Rw ~default:() ~f:(fun env -> remove_impl ~env db key)
+
+  let batch_remove ~env:t db keys =
+    with_env t ~perm:Rw ~default:() ~f:(fun env ->
+        Queue.iter keys ~f:(remove_impl ~env db) )
 end

src/lib/lmdb_storage/generic.mli

@@ -56,6 +56,8 @@ module Read_write : functor (F_func : F) -> sig
 
   val remove : env:t -> ('k, 'v) Db.t -> 'k -> unit
 
+  val batch_remove : env:t -> ('k, 'v) Db.t -> 'k Core_kernel.Queue.t -> unit
+
   val with_txn :
        ?perm:[ `Read | `Write ] Lmdb.perm
     -> f:(Db.getter -> Db.setter -> 'r)