Preparing statements asynchronously

Session objects can be used to prepare a statement asynchronously using Cassandra::Session#prepare_async method. This method returns a Cassandra::Future<Cassandra::Statements::Prepared> instance.

Background

Given

a running cassandra cluster with schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
CREATE TABLE simplex.songs (
  id uuid PRIMARY KEY,
  title text,
  album text,
  artist text,
  tags set<text>,
  data blob
);
INSERT INTO simplex.songs (id, title, album, artist, tags)
VALUES (
   756716f7-2e54-4715-9f00-91dcbea6cf50,
   'La Petite Tonkinoise',
   'Bye Bye Blackbird',
   'Joséphine Baker',
   {'jazz', '2013'})
;
INSERT INTO simplex.songs (id, title, album, artist, tags)
VALUES (
   f6071e72-48ec-4fcb-bf3e-379c8a696488,
   'Die Mösch',
   'In Gold',
   'Willi Ostermann',
   {'kölsch', '1996', 'birds'}
);
INSERT INTO simplex.songs (id, title, album, artist, tags)
VALUES (
   fbdf82ed-0063-4796-9c7c-a3d4f47b4b25,
   'Memo From Turner',
   'Performance',
   'Mick Jager',
   {'soundtrack', '1991'}
);
CREATE TABLE simplex.playlists (
  id uuid,
  title text,
  album text,
  artist text,
  song_id uuid,
  PRIMARY KEY (id, title, album, artist)
);
INSERT INTO simplex.playlists (id, song_id, title, album, artist)
VALUES (
   2cc9ccb7-6221-4ccb-8387-f22b6a1b354d,
   756716f7-2e54-4715-9f00-91dcbea6cf50,
   'La Petite Tonkinoise',
   'Bye Bye Blackbird',
   'Joséphine Baker'
);
INSERT INTO simplex.playlists (id, song_id, title, album, artist)
VALUES (
   2cc9ccb7-6221-4ccb-8387-f22b6a1b354d,
   f6071e72-48ec-4fcb-bf3e-379c8a696488,
   'Die Mösch',
   'In Gold',
   'Willi Ostermann'
);
INSERT INTO simplex.playlists (id, song_id, title, album, artist)
VALUES (
   3fd2bedf-a8c8-455a-a462-0cd3a4353c54,
   fbdf82ed-0063-4796-9c7c-a3d4f47b4b25,
   'Memo From Turner',
   'Performance',
   'Mick Jager'
);
INSERT INTO simplex.playlists (id, song_id, title, album, artist)
VALUES (
   3fd2bedf-a8c8-455a-a462-0cd3a4353c54,
   756716f7-2e54-4715-9f00-91dcbea6cf50,
   'La Petite Tonkinoise',
   'Bye Bye Blackbird',
   'Joséphine Baker'
);

Preparing statements in parallel

Given

the following example:

require 'cassandra'

cluster = Cassandra.cluster
session = cluster.connect("simplex")

# prepare 2 statements in parallel
select_song_future      = session.prepare_async("SELECT * FROM songs WHERE id = ?")
select_playlist_future  = session.prepare_async("SELECT * FROM playlists WHERE id = ?")

# get prepared statements
select_song     = select_song_future.get
select_playlist = select_playlist_future.get

# execute prepared statements
song_id  = Cassandra::Uuid.new('756716f7-2e54-4715-9f00-91dcbea6cf50')
song     = session.execute(select_song, arguments: [song_id]).first

puts "#{song["artist"]}: #{song["title"]} / #{song["album"]} has id #{song_id}"

playlist_id = Cassandra::Uuid.new('2cc9ccb7-6221-4ccb-8387-f22b6a1b354d')
playlist    = session.execute(select_playlist, arguments: [playlist_id])

puts "Playlist #{playlist_id} has #{playlist.size} songs"
playlist.each do |song|
  puts "#{song["artist"]}: #{song["title"]} / #{song["album"]}"
end

When

it is executed

Then

its output should contain:

Joséphine Baker: La Petite Tonkinoise / Bye Bye Blackbird has id 756716f7-2e54-4715-9f00-91dcbea6cf50
Playlist 2cc9ccb7-6221-4ccb-8387-f22b6a1b354d has 2 songs