I can give you a specific example in an instance hosted by you.
This post (id 1067) created by user 3 on 2019-08-03 19:22 UTC received an edit by me (user 2) a few minutes after it was created.
However, no user_action of type 11 was created (unlike the other 2 edits that that user received that day on posts 1001 and 1003)
You can see it more clearly if you run this query:
with my_user_posts as (
select
p.id,
p.user_id
from
posts p
where
p.user_id = 3 -- choose a user id
)
select
up.user_id as my_user_id,
ua.user_id as target_user_id,
pr.post_id,
ua.target_post_id,
pr.user_id as editor_user_id,
ua.acting_user_id,
ua.action_type,
pr.created_at as edit_created_at,
ua.created_at as action_created_at
from
post_revisions pr
inner join my_user_posts up on up.id = pr.post_id
and up.user_id != pr.user_id -- no self edits
and pr.user_id != -1 -- no system edits
left join user_actions ua on ua.target_post_id = pr.post_id
and ua.action_type = 11 -- only EDIT actions
WHERE
pr.created_at between '2019-08-03' and '2019-08-04'
order by
pr.post_id,
pr.created_at
I ran some numbers and, depending on the date, between 7% and 25% of non-self post_revisions don’t have a matching user_action.
