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## 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][execute] or [Session#executeAsync][executeAsync]. The driver provides various
implementations:

* [SimpleStatement](simple/README.md): 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)](prepared/README.md): obtained by binding values to a prepared
  query. Typically used for queries that are executed often, with different values.
* [BatchStatement](batch/README.md): a statement that groups multiple statements to be executed as a batch.

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

* [execution profile](../configuration/README.md) name, or the profile itself if it's been built dynamically.
* [idempotent flag](../idempotence/README.md).
* [tracing flag](../tracing/README.md).
* [query timestamp](../query_timestamps/README.md).
* [page size and paging state](../paging/README.md).
* [per-query keyspace](per_query_keyspace/README.md) (Cassandra 4 or above).
* [token-aware routing](../load_balancing/README.md#token-aware) 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:

```java
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](https://errorprone.info/) -- 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](../configuration/README.md). 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).

[Statement]:        https://docs.datastax.com/en/drivers/java/4.17/com/datastax/oss/driver/api/core/cql/Statement.html
[StatementBuilder]: https://docs.datastax.com/en/drivers/java/4.17/com/datastax/oss/driver/api/core/cql/StatementBuilder.html
[execute]:          https://docs.datastax.com/en/drivers/java/4.17/com/datastax/oss/driver/api/core/session/Session.html#execute-com.datastax.oss.driver.api.core.cql.Statement-
[executeAsync]:     https://docs.datastax.com/en/drivers/java/4.17/com/datastax/oss/driver/api/core/session/Session.html#executeAsync-com.datastax.oss.driver.api.core.cql.Statement-
