DBKV
DBKV
is a disk-based embedded key-value store built on top of :dets
. Inspired by CubDB's intuitive API.
Usage
Create a table with a table name atom
iex> table_name = :my_table
iex> DBKV.create_table(name: table_name, data_dir: "tmp")
:ok
iex> DBKV.exist?(table_name)
true
Upsert a key-value pair
iex> DBKV.put(table_name, "greeting", "Hi")
:ok
iex> DBKV.get(table_name, "greeting")
"Hi"
Insert a key-value pair if it does not exist
iex> DBKV.put_new(table_name, "greeting", "Hello")
{:error, :exists}
iex> DBKV.get(table_name, "greeting")
"Hi"
iex> DBKV.put_new(table_name, "temperature", 32)
:ok
iex> DBKV.get(table_name, "temperature")
32
Update a key-value pair with a function
# Update
iex> DBKV.update(table_name, "greeting", "default", &(&1 <> "!!!"))
:ok
iex> DBKV.get(table_name, "greeting")
"Hi!!!"
iex> DBKV.update(table_name, "language", "default", &(&1 <> "!!!"))
:ok
iex> DBKV.get(table_name, "language")
"default"
Delete a key-value pair
iex> DBKV.delete(table_name, "greeting")
:ok
iex> DBKV.get(table_name, "greeting")
nil
Data persistence across restart
iex> DBKV.delete_table(table_name)
:ok
iex> DBKV.exist?(table_name)
false
iex> DBKV.create_table(name: table_name, data_dir: "tmp")
:ok
iex> DBKV.get(table_name, "temperature")
32
Select records
iex> DBKV.put_new(table_name, 0, "a")
iex> DBKV.put_new(table_name, 1, "b")
iex> DBKV.put_new(table_name, 2, "c")
iex> DBKV.put_new(table_name, 3, "d")
iex> DBKV.put_new(table_name, 4, "e")
# By key range
iex> DBKV.select_by_key_range(table_name, 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(table_name, match_spec)
[{1, "b"}, {2, "c"}, {3, "d"}]
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.