-- Phase 10: notifications counted per thread.
--
-- thread_id is the thread an event that notified a user belongs to: the
-- root its m.relates_to names when rel_type is m.thread, and '' for an
-- event on the main timeline. A read receipt for a thread clears that
-- thread's rows and a receipt for the main timeline clears the '' rows,
-- which is what lets reading one thread leave the rest of the room unread.
ALTER TABLE push_notifications ADD COLUMN thread_id TEXT NOT NULL DEFAULT '';

-- The notifications already stored, from the relation 0012 projected onto
-- their events. A notification whose event has gone stays on the main
-- timeline, where an unthreaded or main receipt still clears it.
UPDATE push_notifications SET thread_id = COALESCE((
    SELECT e.relates_to_id FROM roomserver_events e
    WHERE e.event_id = push_notifications.event_id AND e.rel_type = 'm.thread'
), '');

-- A threaded receipt marks one thread's rows read; the per-thread counts a
-- sync asks for group a room's unread rows by thread.
CREATE INDEX IF NOT EXISTS push_notifications_thread_idx
    ON push_notifications (user_id, room_id, thread_id, is_read, event_pos);