Schema | ScyllaDB Docs

Schema¶

The driver is capable of fetching database schema and presenting it to its users.

Fetching schema¶

Fetching database schema occurs periodically, but it can also be done on-demand. In order to fetch the newest database schema, one can call refresh_metadata() on a Session instance:

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let uri = std::env::var("SCYLLA_URI")
        .unwrap_or_else(|_| "127.0.0.1:9042".to_string());

    let session: Session = SessionBuilder::new().known_node(uri).build().await?;
    // Schema metadata will be fetched below
    session.refresh_metadata().await?;
    Ok(())
}

Inspecting schema¶

Once fetched, a snapshot of cluster’s schema can be examined. The following information can be obtained:

keyspace
- tables belonging to the keyspace
- materialized views belonging to the keyspace
- replication strategy
- user-defined types
table/view
- primary key definition
- columns
- partitioner type

Example showing how to print obtained schema information:

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let uri = std::env::var("SCYLLA_URI")
        .unwrap_or_else(|_| "127.0.0.1:9042".to_string());

    let session: Session = SessionBuilder::new().known_node(uri).build().await?;
    // Schema metadata will be fetched below
    session.refresh_metadata().await?;

    let cluster_data = &session.get_cluster_data();
    let keyspaces = &cluster_data.get_keyspace_info();

    for (keyspace_name, keyspace_info) in keyspaces.iter() {
        println!("Keyspace {}:", keyspace_name);
        println!("\tTables: {:#?}", keyspace_info.tables);
        println!("\tViews: {:#?}", keyspace_info.views);
        println!("\tUDTs: {:#?}", keyspace_info.user_defined_types);
    }

    Ok(())
}

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