Dataloader is a utility to be used for your application's data fetching layer to provide batching and caching, in particular with ocaml-graphql-server. It is a port of facebook/dataloader for Node. The library is still under active development.

This repo contains two packages:

• dataloader, which is IO-agnostic written in CPS-style.
• dataloader-lwt, which is a shim on top of dataloader for Lwt.

Example

The following examples assumes a function batchLoadUsersFromDatabase of the type user_id list -> (user list, exn) result Lwt.t:

let user_loader = Dataloader_lwt.create ~load:(fun user_ids ->
  batchLoadUsersFromDatabase user_ids
)

(* triggers only 1 query rather than 5 *)
List.map (fun user_id ->
  Dataloader_lwt.load user_loader user_id
) [1; 2; 3; 4; 5]

The function ~load provided to Dataloader.create must uphold the following constraints:

• The list of values must be the same length as the list of keys.
• Each index in the list of values must correspond to the same index in the list of keys.