type nonrec error = error
type nonrec write_error = write_error
include Mirage_kv.RW with type write_error := write_error and type error := error
include Mirage_kv.RO with type error := error
include Mirage_device.S
type key = Mirage_kv.Key.t
The type for keys.
val exists : t -> key -> ([ `Value | `Dictionary ] option, error) Stdlib.result Lwt.t
exists t k
is Some `Value
if k
is bound to a value in t
, Some `Dictionary
if k
is a prefix of a valid key in t
and None
if no key with that prefix exists in t
.
exists
answers two questions: does the key exist and is it referring to a value or a dictionary.
An error occurs when the underlying storage layer fails.
val get : t -> key -> (string, error) Stdlib.result Lwt.t
get t k
is the value bound to k
in t
.
The result is Error (`Value_expected k)
if k
refers to a dictionary in t
.
val list : t -> key -> ((string * [ `Value | `Dictionary ]) list, error) Stdlib.result Lwt.t
list t k
is the list of entries and their types in the dictionary referenced by k
in t
.
The result is Error (`Dictionary_expected k)
if k
refers to a value in t
.
val last_modified : t -> key -> (int * int64, error) Stdlib.result Lwt.t
last_modified t k
is the last time the value bound to k
in t
has been modified.
The modification time (d, ps)
is a span for the signed POSIX picosecond span d
* 86_400e12 + ps
. d
is a signed number of POSIX days and ps
a number of picoseconds in the range [0
;86_399_999_999_999_999L
].
When the value bound to k
is a dictionary, the modification time is the latest modification of all entries in that dictionary. This behaviour is only one level deep and not recursive.
val digest : t -> key -> (string, error) Stdlib.result Lwt.t
digest t k
is the unique digest of the value bound to k
in t
.
When the value bound to k
is a dictionary, the digest is a unique and deterministic digest of its entries.
val pp_write_error : write_error Fmt.t
The pretty-printer for pp_write_error
.
val set : t -> key -> string -> (unit, write_error) Stdlib.result Lwt.t
set t k v
replaces the binding k -> v
in t
.
Durability is guaranteed unless set
is run inside an enclosing batch
operation, where durability will be guaranteed at the end of the batch.
val remove : t -> key -> (unit, write_error) Stdlib.result Lwt.t
remove t k
removes any binding of k
in t
. If k
was bound to a dictionary, the full dictionary will be removed.
Durability is guaranteed unless remove
is run inside an enclosing batch
operation, where durability will be guaranteed at the end of the batch.
batch t f
run f
in batch. Ensure the durability of operations.
Since a batch is applied at once, the readings inside a batch will return the state before the entire batch. Concurrent operations will not affect other ones executed during the batch.
Batch applications can fail to apply if other operations are happening concurrently. In case of failure, f
will run again with the most recent version of t
. The result is Error `Too_many_retries
if f
is run for more then retries
attemps (default is 13
).