rkvs.md

Module rkvs

• Data Types
• Function Index
• Function Details

Data Types

fold_options()

fold_options() = [{start_key, key()} | {end_key, key()} | {gt, key()} | {gte, key()} | {lt, key()} | {lte, key()} | {max, integer()} | {fill_cache, true | false}]

key()

key() = term()

keys()

keys() = [key()]

kvs()

kvs() = [{key(), value()}]

ops_kvs()

ops_kvs() = [{put, key(), value()} | {delete, key(), value()}]

value()

value() = term()

Function Index

clear/2	delete the value associated to the key.
clear_range/4	delete all K/Vs in a range.
close/1	close a storage.
contains/2	is the key exists in the storage.
destroy/1	close a storage and remove all the data.
fold/4	fold all K/Vs with a function Additionnaly you can pass the following options: 'gt', (greater than), 'gte' (greather than or equal): define the lower bound of the range to fold. Only the records where the key is greater (or equal to) will be given to the function. 'lt' (less than), 'lte' (less than or equal): define the higher bound of the range to fold. Only the records where the key is less than (or equal to) will be given to the function 'start_key', 'end_key', legacy to 'gte', 'lte' 'max' (default=0), the maximum of records to fold before returning the resut 'fill_cache' (default is true): should be the data cached in memory?
fold_keys/4	fold all keys with a function same parameters as in the fold function.
get/2	get the value associated to the key.
is_empty/1	Returns true if this backend contains any values; otherwise returns false.
open/2	open a storage, amd pass options to the backend.
put/3	store the value associated to the key.
scan/4	retrieve a list of Key/Value in a range.
write_batch/2	do multiple operations on the backend.

Function Details

clear/2

clear(Engine::engine(), Key::key()) -> ok | {error, term()}

delete the value associated to the key

clear_range/4

clear_range(Engine::engine(), Start::key(), End::key(), Max::integer()) -> ok | {error, term()}

delete all K/Vs in a range

close/1

close(Engine::engine()) -> ok | {error, any()}

close a storage

contains/2

contains(Engine::engine(), Key::key()) -> true | false

is the key exists in the storage

destroy/1

destroy(Engine::engine()) -> ok | {error, any()}

close a storage and remove all the data

fold/4

fold(Engine::engine(), Fun::function(), Acc0::any(), Opts::fold_options()) -> any() | {error, term()}

fold all K/Vs with a function Additionnaly you can pass the following options:

• 'gt', (greater than), 'gte' (greather than or equal): define the lower bound of the range to fold. Only the records where the key is greater (or equal to) will be given to the function.

• 'lt' (less than), 'lte' (less than or equal): define the higher bound of the range to fold. Only the records where the key is less than (or equal to) will be given to the function

• 'start_key', 'end_key', legacy to 'gte', 'lte'

• 'max' (default=0), the maximum of records to fold before returning the resut

• 'fill_cache' (default is true): should be the data cached in memory?

fold_keys/4

fold_keys(Engine::engine(), Fun::function(), Acc0::any(), Opts::fold_options()) -> any() | {error, term()}

fold all keys with a function same parameters as in the fold function.

get/2

get(Engine::engine(), Key::key()) -> any() | {error, term()}

get the value associated to the key

is_empty/1

is_empty(Engine::engine()) -> boolean() | {error, term()}

Returns true if this backend contains any values; otherwise returns false.

open/2

open(Name::binary(), Options::list()) -> {ok, engine()} | {error, any()}

open a storage, amd pass options to the backend. The following optinos can be used:

• 'backend': default is rkvs_ets, folowin backend are provided in rkvs: rkvs_ets, rkvs_leveldb, rkvs_rocksdb, rkvs_hanoidb, rvs_bitcask.

• 'db_opts': backend options, refers to the backend doc for them

• 'key_encoding': to encode the key. defautl is raw (binary). can be term, {term, Opts} or sext

• 'value_encoding': to encode the value. defautl is term. can be term, {term, Opts} or sext

put/3

put(Engine::engine(), Key::key(), Value::value()) -> ok | {error, term()}

store the value associated to the key.

scan/4

scan(Engine::engine(), Start::key(), End::key(), Max::integer()) -> kvs() | {error, term()}

retrieve a list of Key/Value in a range

write_batch/2

write_batch(Engine::engine(), Ops::ops_kvs()) -> ok | {error, term()}

do multiple operations on the backend.