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.
Start CubDB by specifying a directory for its database file (if not existing,
it will be created):
{:ok, db} = CubDB.start_link("my/data/directory")get, put, and delete operations work as you probably expect:
CubDB.put(db, :foo, "some value")
#=> :ok
CubDB.get(db, :foo)
#=> "some value"
CubDB.delete(db, :foo)
#=> :ok
CubDB.get(db, :foo)
#=> nilRange 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, min_key: :b, max_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}For more details, read the API documentation.
CubDB can be installed by adding cubdb to your list of dependencies in
mix.exs:
def deps do
[{:cubdb, "~> 0.2.0"}]
end