DBKV

Hex version API docs CI Hex

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.

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