Batches

Batches can be used to group multiple mutations (UPDATE, INSERT, DELETE) together into a single statement; simple or prepared. There are three different types of batches supported by Cassandra 2.0 or later.

• CASS_BATCH_TYPE_LOGGED is used to make sure that multiple mutations across multiple partitions happen atomically, that is, all the included mutations will eventually succeed. However, there is a performance penalty imposed by atomicity guarantee.
• CASS_BATCH_TYPE_UNLOGGED is generally used to group mutations for a single partition and do not suffer from the performance penalty imposed by logged batches, but there is no atomicity guarantee for multi-partition updates.
• CASS_BATCH_TYPE_COUNTER is used to group counters updates.

Important: Be careful when using batches as a performance optimization.

/* This logged batch will makes sure that all the mutations eventually succeed */
CassBatch* batch = cass_batch_new(CASS_BATCH_TYPE_LOGGED);

/* Statements can be immediately freed after being added to the batch */

{
  CassStatement* statement
    = cass_statement_new("INSERT INTO example1(key, value) VALUES ('a', '1')", 0);
  cass_batch_add_statement(batch, statement);
  cass_statement_free(statement);
}

{
  CassStatement* statement
    = cass_statement_new("UPDATE example2 set value = '2' WHERE key = 'b'", 0);
  cass_batch_add_statement(batch, statement);
  cass_statement_free(statement);
}

{
  CassStatement* statement
    = cass_statement_new("DELETE FROM example3 WHERE key = 'c'", 0);
  cass_batch_add_statement(batch, statement);
  cass_statement_free(statement);
}

CassFuture* batch_future = cass_session_execute_batch(session, batch);

/* Batch objects can be freed immediately after being executed */
cass_batch_free(batch);

/* This will block until the query has finished */
CassError rc = cass_future_error_code(batch_future);

printf("Batch result: %s\n", cass_error_desc(rc));

cass_future_free(batch_future);