nips/45.md
Mariano Pérez Rodríguez 1f89a2ad49
Merge remote-tracking branch 'origin/master' into markdownlint
# By Jon Staab (1) and others
# Via fiatjaf
* origin/master:
  nip01: remove misleading markdown example.
  Rephrase Markdown special rule
  Update old link to fiatjaf/nostr
  Clarify how NIP 45 works with multiple COUNT filters. (#504)

# Conflicts:
#	01.md
2023-05-08 11:11:36 -03:00

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# NIP-45
## Event Counts
`draft` `optional` `author:staab`
Relays may support the verb `COUNT`, which provides a mechanism for obtaining event counts.
## Motivation
Some queries a client may want to execute against connected relays are prohibitively expensive, for example, in order to retrieve follower counts for a given pubkey, a client must query all kind-3 events referring to a given pubkey only to count them. The result may be cached, either by a client or by a separate indexing server as an alternative, but both options erode the decentralization of the network by creating a second-layer protocol on top of Nostr.
## Filters and return values
This NIP defines the verb `COUNT`, which accepts a subscription id and filters as specified in [NIP 01](01.md) for the verb `REQ`. Multiple filters are OR'd together and aggregated into a single count result.
```json
["COUNT", <subscription_id>, <filters JSON>...]
```
Counts are returned using a `COUNT` response in the form `{"count": <integer>}`. Relays may use probabilistic counts to reduce compute requirements.
```json
["COUNT", <subscription_id>, {"count": <integer>}]
```
Examples:
```json
# Followers count
["COUNT", <subscription_id>, {"kinds": [3], "#p": [<pubkey>]}]
["COUNT", <subscription_id>, {"count": 238}]
# Count posts and reactions
["COUNT", <subscription_id>, {"kinds": [1, 7], "authors": [<pubkey>]}]
["COUNT", <subscription_id>, {"count": 5}]
```