Expand description
Async Rust driver for the Scylla database written in Rust. Although optimized for Scylla, the driver is also compatible with Apache Cassandra®.
Documentation book
The best source to learn about this driver is the documentation book.
This page contains mainly API documentation
Other documentation
Driver overview
Connecting
All driver activity revolves around the Session
Session
is created by specifying a few known nodes and connecting to them:
use scylla::{Session, SessionBuilder};
use std::error::Error;
#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
let session: Session = SessionBuilder::new()
.known_node("127.0.0.1:9042")
.known_node("1.2.3.4:9876")
.build()
.await?;
Ok(())
}
Session
is usually created using the SessionBuilder.
All configuration options for a Session
can be specified while building.
Making queries
After successfully connecting to the cluster we can make queries.
The driver supports multiple query types:
- Simple
- Simple paged
- Prepare (need to be prepared before use)
- Prepared paged
- Batch
To specify options for a single query create the query object and configure it:
- For simple: Query
- For prepared: PreparedStatement
- For batch: Batch
The easiest way to specify bound values in a query is using a tuple:
// Insert an int and text into the table
session
.query(
"INSERT INTO ks.tab (a, b) VALUES(?, ?)",
(2_i32, "some text")
)
.await?;
But the driver will accept anything implementing the trait ValueList
Receiving results
The easiest way to read rows returned by a query is to cast each row to a tuple of values:
use scylla::IntoTypedRows;
// Read rows containing an int and text
let rows_opt = session
.query("SELECT a, b FROM ks.tab", &[])
.await?
.rows;
if let Some(rows) = rows_opt {
for row in rows.into_typed::<(i32, String)>() {
// Parse row as int and text \
let (int_val, text_val): (i32, String) = row?;
}
}
See the book for more receiving methods
Re-exports
pub use statement::batch;
pub use statement::prepared_statement;
pub use statement::query;
pub use transport::execution_profile::ExecutionProfile;
pub use transport::query_result::QueryResult;
pub use transport::session::IntoTypedRows;
pub use transport::session::Session;
pub use transport::session::SessionConfig;
pub use transport::session_builder::SessionBuilder;
pub use transport::session_builder::CloudSessionBuilder;
cloud
pub use transport::execution_profile;
pub use transport::host_filter;
pub use transport::load_balancing;
pub use transport::retry_policy;
pub use transport::speculative_execution;
Modules
- cloud
cloud
- Collecting history of query executions - retries, speculative, etc.
Macros
- This macro implements FromCqlVal given a type and method of CqlValue that returns this type.
Structs
- A cheaply cloneable and sliceable chunk of contiguous memory.
- A unique reference to a contiguous slice of memory.
- Provides auto caching while executing queries
Traits
- A trait for values that provide sequential write access to bytes.
- This trait defines a way to convert CQL Row into some rust type
Derive Macros
- #[derive(FromRow)] derives FromRow for struct Works only on simple structs without generics etc
- #[derive(FromUserType)] allows to parse a struct as User Defined Type Works only on simple structs without generics etc
- #[derive(IntoUserType)] allows to parse a struct as User Defined Type Works only on simple structs without generics etc
- #[derive(ValueList)] derives ValueList for struct Works only on simple structs without generics etc