Here are OCaml bindings for TrailDB,
an efficient tool for storing and querying series of events.
To build from source.
jbuilder OCaml build system.
$ make # use jbuilder $ make test $ make install # use opam
Or using directly jbuilder:
$ jbuilder build @install $ jbuilder runtest $ jbuilder install
A TrailDB file
is a read only collection of trails,
i.e. keyed series of event records with a timestamp
and sharing a common set of fields.
The API is documented in lib/trailDB.mli.
A TrailDB file is created after a series of event records with
a trail identifier,
and a shared set of fields.
(* Start the creation of a new traildb file to record events with two fields (measure kind and value) plus an implicit timestamp *) let db = TrailDB.Cons.open_w "/tmp/foo" ["measure";"value"] in (* Make some trail identifiers *) let uuid_0 = Uuidm.(v5 ns_oid "trail_0") in let uuid_1 = Uuidm.(v5 ns_oid "trail_1") in (* Insert events with a string value for each field *) TrailDB.Cons.add db uuid_0 123456L ["temperature";"22"]; TrailDB.Cons.add db uuid_1 123456L ["temperature";"12"]; TrailDB.Cons.add db uuid_1 123457L ["temperature";"13"]; TrailDB.Cons.add db uuid_0 123457L ["temperature";"23"]; TrailDB.Cons.add db uuid_0 123458L ["temperature";"24"]; TrailDB.Cons.add db uuid_1 123458L ["temperature";"14"]; TrailDB.Cons.add db uuid_1 123459L ["temperature";"13"]; (* Dump on disk the TrailDB file *) TrailDB.Cons.finalize db
Once build a TrailDB database is read only file.
(* Open a read only TrailDB file *) let db = TrailDB.open_r "/tmp/foo.tdb" in (* Get some meta data *) assert (TrailDB.num_trails db = 2L); assert (TrailDB.num_events db = 7L); assert (TrailDB.num_fields db = 3L); (* timestamp, measure, value *) (* Get the identifier of a trail given its UUIDs *) let trail_uuid = Uuidm.(v5 ns_oid "trail_1") in let (Some trail_id) = TrailDB.get_trail_id db trail_uuid in (* Extract the events of a trail using a cursor *) let cursor = TrailDB.Cursor.create db in TrailDB.Cursor.get_trail cursor trail_id; let rec loop () = match TrailDB.Cursor.next cursor with | None -> () | Some event -> let [measure;value] = event.TrailDB.values |> List.map (TrailDB.get_item_value db) in Printf.printf "(%Ld,%s,%s)\n" event.TrailDB.timestamp measure value |> loop in loop ()