Lightweight transaction (LWT) statement¶

Format of the statement¶

A lightweight transaction statement is not a separate type - it can be expressed just like any other statements: via Statement, PreparedStatement, batches, and so on. The difference lays in the statement string itself - when it contains a condition (e.g. IF NOT EXISTS), it becomes a lightweight transaction. It’s important to remember that CQL specification requires a separate, additional consistency level to be defined for LWT statements - serial_consistency_level. The serial consistency level can only be set to two values: SerialConsistency::Serial or SerialConsistency::LocalSerial. The “local” variant makes the transaction consistent only within the same datacenter. For convenience, Scylla Rust Driver sets the default consistency level to LocalSerial, as it’s more commonly used. For cross-datacenter consistency, please remember to always override the default with SerialConsistency::Serial.

use scylla::statement::unprepared::Statement;
use scylla::statement::{Consistency, SerialConsistency};

// Create a Statement manually to change the Consistency to ONE
let mut my_statement: Statement = Statement::new("INSERT INTO ks.tab (a) VALUES(?) IF NOT EXISTS".to_string());
my_statement.set_consistency(Consistency::One);
// Use cross-datacenter serial consistency
my_statement.set_serial_consistency(Some(SerialConsistency::Serial));

// Insert a value into the table
let to_insert: i32 = 12345;
session.query_unpaged(my_statement, (to_insert,)).await?;

The rest of the API remains identical for LWT and non-LWT statements.

See Statement API documentation for more options