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A lightweight transaction query can be expressed just like any other query, via Session
, with the notable difference of having an additional consistency level parameter - the serial_consistency_level
.
A lightweight transaction query is not a separate type - it can be expressed just like any other queries: via SimpleQuery
, PreparedStatement
, batches, and so on. The difference lays in the query 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 queries - 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::query::Query;
use scylla::statement::{Consistency, SerialConsistency};
// Create a Query manually to change the Consistency to ONE
let mut my_query: Query = Query::new("INSERT INTO ks.tab (a) VALUES(?) IF NOT EXISTS".to_string());
my_query.set_consistency(Consistency::One);
// Use cross-datacenter serial consistency
my_query.set_serial_consistency(Some(SerialConsistency::Serial));
// Insert a value into the table
let to_insert: i32 = 12345;
session.query_unpaged(my_query, (to_insert,)).await?;
The rest of the API remains identical for LWT and non-LWT queries.
See Query API documentation for more options
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