Batch statements
Session objects can be used to construct a logged batch statement and later execute it.
Background
- Given
- a running cassandra cluster with schema:
CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3}; USE simplex; CREATE TABLE songs ( id uuid PRIMARY KEY, title text, album text, artist text, tags set<text>, data blob ); CREATE TABLE cas_batch (k text, v int, PRIMARY KEY (k, v));
since cassadra v2.0
A batch of simple statements is executed
- Given
- the following example:
require 'cassandra' cluster = Cassandra.cluster at_exit { cluster.close } session = cluster.connect("simplex") rows = session.execute("SELECT * FROM songs") puts "songs contain #{rows.size} rows" batch = session.batch do |b| b.add("INSERT INTO songs (id, title, album, artist, tags) VALUES ( 756716f7-2e54-4715-9f00-91dcbea6cf50, 'La Petite Tonkinoise', 'Bye Bye Blackbird', 'Joséphine Baker', {'jazz', '2013'} )") b.add("INSERT INTO songs (id, title, album, artist, tags) VALUES ( f6071e72-48ec-4fcb-bf3e-379c8a696488, 'Die Mösch', 'In Gold', 'Willi Ostermann', {'kölsch', '1996', 'birds'} )") b.add("INSERT INTO songs (id, title, album, artist, tags) VALUES ( fbdf82ed-0063-4796-9c7c-a3d4f47b4b25, 'Memo From Turner', 'Performance', 'Mick Jager', {'soundtrack', '1991'} )") end puts "inserting rows in a batch" session.execute(batch, consistency: :all) rows = session.execute("SELECT * FROM songs") puts "songs contain #{rows.size} rows"
- When
- it is executed
- Then
- its output should contain:
songs contain 0 rows inserting rows in a batch songs contain 3 rows
since cassadra v2.0
A batch of simple statements with parameters is executed
- Given
- the following example:
require 'cassandra' cluster = Cassandra.cluster at_exit { cluster.close } session = cluster.connect("simplex") rows = session.execute("SELECT * FROM songs") puts "songs contain #{rows.size} rows" batch = session.batch do |b| b.add("INSERT INTO songs (id, title, album, artist, tags) VALUES (?, ?, ?, ?, ?)", Cassandra::Uuid.new('756716f7-2e54-4715-9f00-91dcbea6cf50'), 'La Petite Tonkinoise', 'Bye Bye Blackbird', 'Joséphine Baker', Set['jazz', '2013'] ) b.add("INSERT INTO songs (id, title, album, artist, tags) VALUES (?, ?, ?, ?, ?)", Cassandra::Uuid.new('f6071e72-48ec-4fcb-bf3e-379c8a696488'), 'Die Mösch', 'In Gold', 'Willi Ostermann', Set['kölsch', '1996', 'birds'] ) b.add("INSERT INTO songs (id, title, album, artist, tags) VALUES (?, ?, ?, ?, ?)", Cassandra::Uuid.new('fbdf82ed-0063-4796-9c7c-a3d4f47b4b25'), 'Memo From Turner', 'Performance', 'Mick Jager', Set['soundtrack', '1991'] ) end puts "inserting rows in a batch" session.execute(batch, consistency: :all) rows = session.execute("SELECT * FROM songs") puts "songs contain #{rows.size} rows"
- When
- it is executed
- Then
- its output should contain:
songs contain 0 rows inserting rows in a batch songs contain 3 rows
since cassadra v2.0
A prepared statement is executed in a batch
- Given
- the following example:
require 'cassandra' cluster = Cassandra.cluster at_exit { cluster.close } session = cluster.connect("simplex") rows = session.execute("SELECT * FROM songs") puts "songs contain #{rows.size} rows" insert = session.prepare("INSERT INTO songs (id, title, album, artist, tags) VALUES (?, ?, ?, ?, ?)") batch = session.batch do |b| b.add(insert, Cassandra::Uuid.new('756716f7-2e54-4715-9f00-91dcbea6cf50'), 'La Petite Tonkinoise', 'Bye Bye Blackbird', 'Joséphine Baker', Set['jazz', '2013'] ) b.add(insert, Cassandra::Uuid.new('f6071e72-48ec-4fcb-bf3e-379c8a696488'), 'Die Mösch', 'In Gold', 'Willi Ostermann', Set['kölsch', '1996', 'birds'] ) b.add(insert, Cassandra::Uuid.new('fbdf82ed-0063-4796-9c7c-a3d4f47b4b25'), 'Memo From Turner', 'Performance', 'Mick Jager', Set['soundtrack', '1991'] ) end puts "inserting rows in a batch" session.execute(batch, consistency: :all) rows = session.execute("SELECT * FROM songs") puts "songs contain #{rows.size} rows"
- When
- it is executed
- Then
- its output should contain:
songs contain 0 rows inserting rows in a batch songs contain 3 rows
since cassadra v2.0.9
A cas batch is never applied more than once
- Given
- the following example:
require 'cassandra' cluster = Cassandra.cluster at_exit { cluster.close } session = cluster.connect("simplex") statement = session.prepare("INSERT INTO cas_batch (k, v) VALUES (?, ?) IF NOT EXISTS") batch = session.batch batch.add("INSERT INTO cas_batch (k, v) VALUES ('key1', 0)") batch.add(statement, "key1", 1) batch.add(statement, "key1", 2) results = session.execute(batch) rows = results.first puts "batch applied? #{rows["[applied]"]}" results = session.execute(batch) rows = results.first puts "batch applied? #{rows["[applied]"]}"
- When
- it is executed
- Then
- its output should contain:
batch applied? true batch applied? false