CubDB

CubDB is a pure-Elixir embedded key-value database, designed for simplicity. It runs locally, and is backed by a single file.

Both keys and values can be any Elixir (or Erlang) term, so no serialization and de-serialization is necessary.

The CubDB database file uses an immutable data structure that ensures robustness to data corruption: entries are never changed in-place, and writes are atomic.

Read operations are performed on immutable "snapshots", so they are always consistent, run concurrently, and do not block write operations, nor are blocked by them.

Examples

Start CubDB by specifying a data directory for its file:

{:ok, db} = CubDB.start_link("my/data/directory")

get, put, and delete operations work as you expect:

CubDB.put(db, :foo, "some value")
#=> :ok

CubDB.get(db, :foo)
#=> "some value"

CubDB.delete(db, :foo)
#=> :ok

CubDB.get(db, :foo)
#=> nil

Range of keys are retrieved using select:

for {key, value} <- [a: 1, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8] do
  CubDB.put(db, key, value)
end

CubDB.select(db, from_key: :b, to_key: :e)
#=> {:ok, [b: 2, c: 3, d: 4, e: 5]}

But select can do much more than that. It can apply a pipeline of operations (map, filter, take, drop and more) to the selected entries, it can select the entries in normal or reverse order, and it can reduce the result using an arbitrary function:

# Take the sum of the last 3 even values:

CubDB.select(db,
  reverse: true,
  pipe: [
    map: fn {_key, value} -> value end,
    filter: &Integer.is_even/1,
    take: 3
  ],
  reduce: fn n, sum -> sum + n end
)
#=> {:ok, 18}

Installation

If available in Hex, the package can be installed by adding cubdb to your list of dependencies in mix.exs:

def deps do
  [{:cubdb, "~> 0.1.0"}]
end