elixir-cassandra's Introduction

Cassandra

An Elixir driver for Apache Cassandra.

This driver works with Cassandra Query Language version 3 (CQL3) and Cassandra's native protocol v4.

Features

Automatic peer discovery
Automatic connection managment (reconnect on connection loss and discover new nodes)
Configurable load-balancing/reconnection policies
Asynchronous execution through Tasks
Prepared statements with named and position based values
Token based load-balancing policy
Automatic prepare and cache prepared statements per host
Result paging

Installation

Add cassandra to your list of dependencies in mix.exs:

def deps do
  [{:cassandra, "~> 1.0.0-beta.5"}]
end

Quick Start

defmodule Repo do
  use Cassandra
end

{:ok, _} = Repo.start_link
# uses "127.0.0.1:9042" as contact point by default
# discovers other nodes on first connection

Repo.execute """
  CREATE KEYSPACE IF NOT EXISTS test
    WITH replication = {'class':'SimpleStrategy','replication_factor':1};
  """, consistency: :all

Repo.execute """
  CREATE TABLE IF NOT EXISTS test.users (
    id timeuuid,
    name varchar,
    age int,
    PRIMARY KEY (id)
  );
  """, consistency: :all

insert = "INSERT INTO test.users (id, name, age) VALUES (?, ?, ?);"

users = [
  %{name: "Bilbo", age: 50},
  %{name: "Frodo", age: 33},
  %{name: "Gandolf", age: 2019},
]

users
|> Task.async_stream(&Repo.execute(insert, values: [Cassandra.UUID.v1, &1.name, &1.age]))
|> Enum.to_list

Repo.execute("SELECT * FROM test.users;")

# %CQL.Result.Rows{
#   columns: ["id", "age", "name"],
#   rows_count: 3,
#   rows: [
#     ["831e5df2-a0e1-11e6-b9af-6d2c86545d91", 2019, "Gandolf"],
#     ["831e5df1-a0e1-11e6-b9af-6d2c86545d91", 33, "Frodo"],
#     ["831e5df0-a0e1-11e6-b9af-6d2c86545d91", 50, "Bilbo"]
#   ]
# }