DBKV
DBKV
is a disk-based embedded key-value store built on top of :dets
. Inspired by CubDB's intuitive API.
Usage
Open a file
iex> {:ok, t} = DBKV.open(name: :my_table, data_dir: "tmp")
{:ok, :my_table}
iex> DBKV.exist?(t)
true
Upsert a key-value pair
iex> DBKV.put(t, "greeting", "Hi")
:ok
iex> DBKV.get(t, "greeting")
"Hi"
Insert a key-value pair if it does not exist
iex> c
{:error, :exists}
iex> DBKV.get(t, "greeting")
"Hi"
iex> DBKV.put_new(t, "temperature", 32)
:ok
iex> DBKV.get(t, "temperature")
32
Update a key-value pair with a function
iex> DBKV.update(t, "greeting", "default", &(&1 <> "!!!"))
:ok
iex> DBKV.get(t, "greeting")
"Hi!!!"
iex> DBKV.update(t, "language", "default", &(&1 <> "!!!"))
:ok
iex> DBKV.get(t, "language")
"default"
Delete a key-value pair
iex> DBKV.delete(t, "greeting")
:ok
iex> DBKV.get(t, "greeting")
nil
Persistence across restart
iex> DBKV.close(t)
:ok
iex> DBKV.exist?(t)
false
iex> DBKV.open(name: t, data_dir: "tmp")
{:ok, :my_table}
iex> DBKV.get(t, "temperature")
32
Select records
iex> DBKV.put_new(t, 0, "a")
iex> DBKV.put_new(t, 1, "b")
iex> DBKV.put_new(t, 2, "c")
iex> DBKV.put_new(t, 3, "d")
iex> DBKV.put_new(t, 4, "e")
By key range
iex> DBKV.select_by_key_range(t, 1, 3)
[{1, "b"}, {2, "c"}, {3, "d"}]
By match spec
iex> require Ex2ms
iex> match_spec = Ex2ms.fun do {k, v} = kv when 1 <= k and k <= 3 -> kv end
[{{:"$1", :"$2"}, [{:andalso, {:"=<", 1, :"$1"}, {:"=<", :"$1", 3}}], [:"$_"]}]
iex> DBKV.select_by_match_spec(t, match_spec)
[{1, "b"}, {2, "c"}, {3, "d"}]
Argument Error
When a table is not started, underlying :dets
will raise an argument error. Please make sure that the table is started with a correct name.
iex> DBKV.get(:nonexistent_table, "temperature")
** (ArgumentError) argument error
(stdlib 3.15.1) dets.erl:1259: :dets.lookup(:nonexistent_table, "temperature")
(dbkv 0.1.2) lib/dvkv.ex:78: DBKV.get/3
Using :dets
functions
DBKV
is a thin wrapper of :dets
. You can mix and match with any :dets
functions if you wish.
iex> :dets.info(t)
[
type: :set,
keypos: 1,
size: 0,
file_size: 5464,
filename: 'tmp/my_table.db'
]
Installation
DBKV
can be installed by adding dbkv
to your list of dependencies in mix.exs:
def deps do
[
{:dbkv, "~> 0.1"}
]
end
Documentation can be found at https://hexdocs.pm/dbkv.