Пользователи, которые работают когда не в статусе Busy.

q.sql

with
  states_and_events as (
    select userid, ctime, state, null as patch from "UserState"
      union all
        select userid, ctime, null, patch
          from "Event"
          where patch::text <> '{"id":' || modelid || '}'
    ),
  state_groups as (
    select s.*, count(state) over (partition by userid order by ctime) as state_grp
      from states_and_events s
      where ctime > '2019-05-01' and ctime < '2019-06-01'
    ),
  events_with_states as (
    select userid, ctime, max(state) over (partition by userid, state_grp) as state, patch
      from state_groups
    )
  select *
    from events_with_states
    where patch is not null
      and state <> 'Busy'
    order by userid, ctime;