Prefix filter for Iterator

I am trying to implement a prefix scan and delete. While a generalised search was ruled out years ago, I would argue the iterator returning all values is not viable for large caches.

My proposal is to add a prefix filter option to iterator (any maybe clear) - that would be implemented as a per-invocation extension of the namespace.

Here is my use-case (albeit using a non backward-compatible signature, for ilustrative purposes):


export class KeyvSessionService {

  // get all user active sessions
  async list(userId: string): Promise<Array<[string, Session]>> {
    if (!this.keyv.iterator) {
      throw new Error('Provider does not support iterator');
    }
    const sessions: Array<[string, Session]> = [];
    for await (const [key, value] of this.keyv.iterator({ prefix: userId })) {
      sessions.push([key, value]);
    }
    return sessions;
  }

  // remove all user sessions
  async clear(userId: string): Promise<void> {
    await this.keyv.delete((await this.list(userId)).map(([key]) => key));

    // this would be cleanest, providers could decide the best way to implement this
    // return keyv.clear({ prefix: userId });
  }

  // crud
  keyv: Keyv<Session>;
  constructor(private readonly store: KeyvStoreAdapter) {this.keyv = new Keyv({ store: this.store, namespace: 'session' }); }
  set(userId: string, sessionId: string, session: Session): Promise<boolean> {return this.keyv.set(`${userId}:${sessionId}`, session);}
  get(userId: string, sessionId: string): Promise<Session | undefined> {return this.keyv.get(`${userId}:${sessionId}`);}
  delete(userId: string, sessionId: string): Promise<boolean> {return this.keyv.delete(`${userId}:${sessionId}`);}
}

I would be happy to contribute to this cause.

Note: I explored using a new Keyv({ store: this.store, namespace: 'session:${userId}' }); per invocation but creating/destroying has overhead/side effects that make this pattern unviable in my mind.

jaredwray / keyv

Prefix filter for Iterator #1181