Scylla allows users to define their own data types with named fields.
The driver supports this by allowing to create a custom struct with derived functionality.
For example let’s say my_type was created using this query:
CREATE TYPE ks.my_type (int_val int, text_val text)
To use this type in the driver create a matching struct and derive IntoUserType and FromUserType:
# extern crate scylla;
# use scylla::Session;
# use std::error::Error;
# async fn check_only_compiles(session: &Session) -> Result<(), Box<dyn Error>> {
use scylla::IntoTypedRows;
use scylla::macros::{FromUserType, IntoUserType};
use scylla::cql_to_rust::FromCqlVal;
// Define custom struct that matches User Defined Type created earlier
// wrapping field in Option will gracefully handle null field values
#[derive(Debug, IntoUserType, FromUserType)]
struct MyType {
int_val: i32,
text_val: Option<String>,
}
// Now it can be sent and received like any other value
// Insert my_type into the table
let to_insert = MyType {
int_val: 17,
text_val: Some("Some string".to_string()),
};
session
.query("INSERT INTO keyspace.table (a) VALUES(?)", (to_insert,))
.await?;
// Read MyType from the table
if let Some(rows) = session.query("SELECT a FROM keyspace.table", &[]).await?.rows {
for row in rows.into_typed::<(MyType,)>() {
let (my_type_value,): (MyType,) = row?;
}
}
# Ok(())
# }