You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ddl.rs
    path of file: ./repos/materialize/src/adapter/src/coord
    
    the code of the file until where you have to start completion: // Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of th
    
    async fn drop_replica(&mut self, cluster_id: ClusterId, replica_id: ReplicaId) {
        if let Some(Some(ReplicaMetadata { metrics })) =
            self.transient_replica_metadata.insert(replica_id, None)
        {
            let mut updates = vec![];
            if let Some(metrics) = metrics {
                let retraction = self
                    .catalog()
                    .state()
                    .pack_replica_metric_updates(replica_id, &metrics, -1);
                updates.extend(retraction.into_iter());
            }
            self.builtin_table_update().background(updates);
        }
        self.controller
            .drop_replica(cluster_id, replica_id)
            .await
            .expect("dropping replica must not fail");
    }