irmin

Irmin, a distributed database that follows the same design principles as Git
IN THIS PACKAGE
Module Irmin . S . Backend . Node_portable

Node values

type t

The type for node values.

val t : t Irmin__Type.t
val metadata_t : Schema.Metadata.t Irmin__Type.t
type contents_key = Hash.t

The type for contents keys.

val contents_key_t : contents_key Irmin__Type.t
type node_key = Hash.t

The type for node keys.

val node_key_t : node_key Irmin__Type.t
val step_t : Schema.Path.step Irmin__Type.t
type value = [
| `Node of node_key
| `Contents of contents_key * Schema.Metadata.t
]

The type for either (node) keys or (contents) keys combined with their metadata.

val value_t : value Irmin__Type.t
val hash_t : Hash.t Irmin__Type.t
val of_list : (Schema.Path.step * value) list -> t

of_list l is the node n such that list n = l.

val list : ?offset:int -> ?length:int -> ?cache:bool -> t -> (Schema.Path.step * value) list

list t is the contents of t. offset and length are used to paginate results.

val of_seq : (Schema.Path.step * value) Irmin__Import.Seq.t -> t

of_seq s is the node n such that seq n = s.

val seq : ?offset:int -> ?length:int -> ?cache:bool -> t -> (Schema.Path.step * value) Irmin__Import.Seq.t

seq t is the contents of t. offset and length are used to paginate results.

See caching for an explanation of the cache parameter

val empty : unit -> t

empty () is the empty node.

val is_empty : t -> bool

is_empty t is true iff t is empty.

val length : t -> int

length t is the number of entries in t.

val hash_exn : ?force:bool -> t -> Hash.t

hash_exn t is the hash of t.

Another way of computing it is Hash.Typed(Hash)(Node).hash t which computes the pre-hash of t before hashing it using Hash. hash_exn might be faster because the it may be optimised (e.g. it may use caching).

hash_exn t is hash_exn ~force:true t which is not expected to raise an exception. hash_exn ~force:false t will raise Not_found if the hash requires IOs to be computed.

val clear : t -> unit

Cleanup internal caches.

val find : ?cache:bool -> t -> Schema.Path.step -> value option

find t s is the value associated with s in t.

A node can point to user-defined contents. The edge between the node and the contents is labeled by a step.

See caching for an explanation of the cache parameter

val add : t -> Schema.Path.step -> value -> t

add t s v is the node where find t v is Some s but is similar to t otherwise.

val remove : t -> Schema.Path.step -> t

remove t s is the node where find t s is None but is similar to t otherwise.

module Metadata : sig ... end

Metadata functions.

caching

cache regulates the caching behaviour regarding the node's internal data which may be lazily loaded from the backend, depending on the node implementation.

cache defaults to true which may greatly reduce the IOs and the runtime but may also increase the memory consumption.

cache = false doesn't replace a call to clear, it only prevents the storing of new data, it doesn't discard the existing one.

Recursive Nodes

Some Node implementations (like irmin-pack's inodes) can represent a node as a set of nodes. One operation on such "high-level" node corresponds to a sequence of recursive calls to the underlying "lower-level" nodes. Note: theses effects are not in the Lwt monad on purpose (so Tree.hash and Tree.equal are not in the Lwt monad as well).

type effect := expected_depth:int -> node_key -> t option

The type for read effects.

val with_handler : ( effect -> effect ) -> t -> t

with_handler f replace the current effect handler h by f h. f h will be called for all the recursive read effects that are required by recursive operations on nodes. .

type head := [
| `Node of (Schema.Path.step * value) list
| `Inode of int * (int * Hash.t) list
]
val head : t -> head

Reveal the shallow internal structure of the node.

Only hashes and not keys are revealed in the `Inode case, this is because these inodes might not be keyed yet.

val of_node : Node.value -> t

merging

val merge : contents:contents_key option Irmin__Merge.t -> node:node_key option Irmin__Merge.t -> t Irmin__Merge.t

merge is the merge function for nodes.

Proofs

type proof = [
| `Blinded of Hash.t
| `Values of (Schema.Path.step * value) list
| `Inode of int * (int * proof) list
]

The type for proof trees.

val proof_t : proof Irmin__Type.t
val to_proof : t -> proof
val of_proof : depth:int -> proof -> t option

of_proof ~depth p is None if p is corrupted or incompatible with depth. It is Some t when t is a node if the operation succeeded.

hash_exn t never raises Not_found