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Prepared statements can be used to improve the performance of frequently executed queries. Preparing the query caches it on the Cassandra cluster and only needs to be performed once. Once created, prepared statements should be reused with different bind variables. Prepared queries use the ? marker to denote bind variables in the query string. You can also specify bind variables as :name.
void prepare_statement(CassSession* session) {
/* Prepare the statement on the Cassandra cluster */
CassFuture* prepare_future
= cass_session_prepare(session, "INSERT INTO example (key, value) VALUES (?, ?)");
/* Wait for the statement to prepare and get the result */
CassError rc = cass_future_error_code(prepare_future);
printf("Prepare result: %s\n", cass_error_desc(rc));
if (rc != CASS_OK) {
/* Handle error */
cass_future_free(prepare_future);
return;
}
/* Get the prepared object from the future */
const CassPrepared* prepared = cass_future_get_prepared(prepare_future);
/* The future can be freed immediately after getting the prepared object */
cass_future_free(prepare_future);
/* The prepared object can now be used to create statements that can be executed */
CassStatement* statement = cass_prepared_bind(prepared);
/* Bind variables by name this time (this can only be done with prepared statements)*/
cass_statement_bind_string_by_name(statement, "key", "abc");
cass_statement_bind_int32_by_name(statement, "value", 123);
/* Execute statement - same as the non-prepared code.
Here we'll discard the result. */
CassFuture* execute_future = cass_session_execute(session, statement);
cass_future_wait(execute_future);
cass_future_free(execute_future);
/* The prepared object must be freed */
cass_prepared_free(prepared);
}
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