synapse/docs/admin_api/purge_history_api.md

Purge History API

The purge history API allows server admins to purge historic events from their database, reclaiming disk space.

Depending on the amount of history being purged a call to the API may take several minutes or longer. During this period users will not be able to paginate further back in the room from the point being purged from.

Note that Synapse requires at least one message in each room, so it will never delete the last message in a room.

The API is:

POST /_synapse/admin/v1/purge_history/<room_id>[/<event_id>]

To use it, you will need to authenticate by providing an access_token for a server admin: Admin API

By default, events sent by local users are not deleted, as they may represent the only copies of this content in existence. (Events sent by remote users are deleted.)

Room state data (such as joins, leaves, topic) is always preserved.

To delete local message events as well, set delete_local_events in the body:

{
   "delete_local_events": true
}

The caller must specify the point in the room to purge up to. This can be specified by including an event_id in the URI, or by setting a purge_up_to_event_id or purge_up_to_ts in the request body. If an event id is given, that event (and others at the same graph depth) will be retained. If purge_up_to_ts is given, it should be a timestamp since the unix epoch, in milliseconds.

The API starts the purge running, and returns immediately with a JSON body with a purge id:

{
    "purge_id": "<opaque id>"
}

Purge status query

It is possible to poll for updates on recent purges with a second API;

GET /_synapse/admin/v1/purge_history_status/<purge_id>

Again, you will need to authenticate by providing an access_token for a server admin.

This API returns a JSON body like the following:

{
    "status": "active"
}

The status will be one of active, complete, or failed.

If status is failed there will be a string error with the error message.

Reclaim disk space (Postgres)

To reclaim the disk space and return it to the operating system, you need to run VACUUM FULL; on the database.

https://www.postgresql.org/docs/current/sql-vacuum.html