Statements¶

Quick overview¶

What you pass to session.execute().

• three types: simple (textual query), bound (prepared) and batch.

• built-in implementations are immutable. Setters always return a new object, don’t ignore the result.

To execute a CQL query, you create a Statement instance and pass it to Session#execute or Session#executeAsync. The driver provides various implementations:

• SimpleStatement: a simple implementation built directly from a character string. Typically used for queries that are executed only once or a few times.

• BoundStatement (from PreparedStatement): obtained by binding values to a prepared query. Typically used for queries that are executed often, with different values.

• BatchStatement: a statement that groups multiple statements to be executed as a batch.

All statement types share a common set of execution attributes, that can be set through either setters or a builder:

• execution profile name, or the profile itself if it’s been built dynamically.

• idempotent flag.

• tracing flag.

• query timestamp.

• page size and paging state.

• per-query keyspace (Cassandra 4 or above).

• token-aware routing information (keyspace and key/token).

• normal and serial consistency level.

• query timeout.

• custom payload to send arbitrary key/value pairs with the request (you should only need this if you have a custom query handler on the server).

When setting these attributes, keep in mind that statements are immutable, and every method returns a different instance:

SimpleStatement statement =
    SimpleStatement.newInstance("SELECT release_version FROM system.local");

// Won't work: statement isn't modified in place
statement.setConfigProfileName("oltp");
statement.setIdempotent(true);

// Instead, reassign the statement every time:
statement = statement.setConfigProfileName("oltp").setIdempotent(true);

All of these mutating methods are annotated with @CheckReturnValue. Some code analysis tools – such as ErrorProne – can check correct usage at build time, and report mistakes as compiler errors.

Note that some attributes can either be set programmatically, or inherit a default value defined in the configuration. Namely, these are: idempotent flag, query timeout, consistency levels and page size. We recommended the configuration approach whenever possible (you can create execution profiles to capture common combinations of those options).