NIP-114
=======

ids_only filter
---------------

### Description

When a filter has `ids_only: true`, the relay must return only the ids of the events that match the filter.

The ids are returned as `["HAVE", subscriptionID, eventID]` messages.

Clients may request the full events by id with a `["GET", eventId]` message. Relays reply to `GET` requests with `["EVENT", "*", eventJson]` messages, where `*` is a placeholder subscription id.

Clients may also request the full events by id with a normal `["REQ", subscriptionId, {ids}]` message.

### Motivation

`ids_only` filter allows a client to request the full event only when it is not already stored locally or received from another relay. This can save a lot of bandwidth, especially when connecting to multiple relays or subscribing to a lot of data.

### Implementations

- [@mmalmi/strfry](https://github.com/mmalmi/strfry) ([Pull request](https://github.com/hoytech/strfry/pull/99))
- [@mmalmi/nostr-rs-relay](https://github.com/mmalmi/nostr-rs-relay) ([Pull request](https://github.com/scsibug/nostr-rs-relay/pull/186))
- [Snort & Iris](https://git.v0l.io/Kieran/snort).
  - [HAVE message handling](https://git.v0l.io/Kieran/snort/src/commit/edbfa02c5202c5a7035e146d446e7bf4bb3feb84/packages/system/src/connection-pool.ts#L74)
  - [Adding ids_only filter](https://git.v0l.io/Kieran/snort/src/commit/edbfa02c5202c5a7035e146d446e7bf4bb3feb84/packages/system/src/query.ts#L397) for relays that support nip 114