CubDB is an embedded key-value database written in the Elixir language. It
runs locally, it is schema-less, and backed by a single file.
Both keys and values can be any arbitrary Elixir (or Erlang) term.
The most relevant features offered by CubDB are:
-
Simple
get,put, anddeleteoperations -
Arbitrary selection of entries and transformation of the result with
select -
Atomic multiple updates with
get_and_update_multi -
Concurrent read operations, that do not block nor are blocked by writes
The CubDB database file uses an immutable data structure that guaratees
robustness to data corruption, as entries are never changed in-place. It also
makes read operations consistent, even while write operations are being
performed concurrently, as ranges of entries are selected on immutable
snapshots.
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: fn value ->
is_integer(value) && Integer.is_even(value)
end,
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, "~> 0.6.0"}]
endThe file data structure used by CubDB is inspired by
CouchDB. A big thanks goes to the CouchDB
maintainers for the readable codebase and extensive documentation.