irmin

Irmin, a distributed database that follows the same design principles as Git
IN THIS PACKAGE
Module Irmin . Generic_key . Maker . X . Node_store . Make

Parameters

module Hash : Hash.S
module Value : Type.S

Signature

Read-only stores

Read-only stores are store where it is only possible to read existing values.

type -'a t

The type for stores. The 'a phantom type carries information about the store mutability.

type key = Hash.t key

The type for keys.

type value = Value.t

The type for raw values.

val mem : [> Perms.read ] t -> key -> bool Lwt.t

mem t k is true iff k is present in t.

val find : [> Perms.read ] t -> key -> value option Lwt.t

find t k is Some v if k is associated to v in t and None is k is not present in t.

val close : 'a t -> unit Lwt.t

close t frees up all the resources associated with t. Any operations run on a closed handle will raise Closed.

type hash = Hash.t

The type of hashes of value.

val add : [> Perms.write ] t -> value -> key Lwt.t

Write the contents of a value to the store, and obtain its key.

val unsafe_add : [> Perms.write ] t -> hash -> value -> key Lwt.t

Same as add but allows specifying the value's hash directly. The backend might choose to discard that hash and/or can be corrupt if the hash is not consistent.

val index : [> Perms.read ] t -> hash -> key option Lwt.t

Indexing maps the hash of a value to a corresponding key of that value in the store. For stores that are addressed by hashes directly, this is typically fun _t h -> Lwt.return (Key.of_hash h); for stores with more complex addressing schemes, index may attempt a lookup operation in the store.

In general, indexing is best-effort and reveals no information about the membership of the value in the store. In particular:

  • index t hash = Some key doesn't guarantee mem t key: the value with hash hash may still be absent from the store;
  • index t hash = None doesn't guarantee that there is no key such that mem t key and Key.to_hash key = hash: the value may still be present in the store under a key that is not indexed.
val clear : 'a t -> unit Lwt.t

Clear the store. This operation is expected to be slow.

val batch : Perms.read t -> ( [ Perms.read | Perms.write ] t -> 'a Lwt.t ) -> 'a Lwt.t

batch t f applies the writes in f in a separate batch. The exact guarantees depend on the implementation.

module Key : Key.S with type t = key and type hash = hash
val v : Irmin__Conf.t -> Perms.read t Lwt.t

v config is a function returning fresh store handles, with the configuration config, which is provided by the backend.