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Prepared StatementsΒΆ
Prepared statements can be used to improve the performance of frequently executed queries. Preparing the query caches it on the ScyllaDB/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 ScyllaDB/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);
}