I thought that every time a user edits someone else’s post, this action would be recorded in the user_actions table, but I’ve just realized this only happens sporadically (only for some users some of the time).
Is this the intended behavior or is there another condition I’m not considering?
It’s hard to give a step-by-step to reproduce this issue, but this is how I detected it:
Find a post with an edit notification:
Query user_actions for the given acting_user_id (the editor), the given user_id (the edited) and the given topic_id. In my case:
select * from user_actions ua
where ua.acting_user_id = 229
and ua.user_id = 259
and ua.target_topic_id = 1907;
This is what I get:
Action type 2 means that the edited user received a LIKE from the editor.
Action type 6 means that the editor responded to the edited user.
I just realized that either I don’t fully understand the cases where an edit notification is created or this is a much more widespread problem than I thought.
Main assumptions
If User A edits what User B wrote, several things happen:
A new row gets added to the post_revisions table.
A new row gets added to the user_actions table with action_type = 11.
By going to /u/userB/notifications/edits, User B will be able to see that a new edit was made by User A (this depends on user_actions).
By clicking on the pencil icon in his post, User B will be able to see the actual edit that User A performed (this depends on post_revisions).
Test
If the above assumptions are correct, this query should show all the rows in the post_revisions table for posts created by User B (in this case, id 259) that were edited by any user (other than himself, or the system user), along with the corresponding rows in user_actions for action_type = 11.
with my_user_posts as (
select
p.id,
p.user_id
from
posts p
where
p.user_id = 259 -- 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
order by
pr.post_id,
pr.created_at;
Expected output
Every row has both post_revisions data along with user_actions data.
Actual output
Some of the post_revisions rows doesn’t have matching user_actions data. Therefore, the user can see the revisions by clicking on the pencil in each post, but wasn’t notified about receiving several edits.
Adding an additional edit to an old post without user_action data. Result: the user_action data also did not appear.
Creating a fake user, copying the pre-edit content of a post without user_action data, creating a post with it and applying the same edit that was done with a different user. Result: the user_action data appeared correctly.
Repeating the above procedures when the user is active or offline. Result: no change.
Repeating the above procedures changing the editing grace period. Result: no change.
Conclusions
The issue doesn’t appear to be:
user-specific. It happens to practically every user.
connection-specific. The fact that the user is active or offline doesn’t change the output.
time-specific. Changing the editing grace period had no effect.
The issue appears to be
action-specific. I have not seen any issues notifying any of the other actions (LIKE, WAS_LIKED, RESPONSE, REPLY, MENTION or QUOTE). The only problem is with EDIT actions.
post-specific. It doesn’t happen to every post, only specific ones (seemingly at random)
One possibility is that something is happening during the creation of specific posts to prevent EDIT user_actions from being saved, but I have no idea what this could be.
It’s also possible that this is happening by design and that there are specific conditions under which users are not notified of edits, but I haven’t seen this documented anywhere.
Next steps
If you know a reason why edit notifications might not get triggered every time there is an edit, please let me know.
If you have your own Discourse instance, could you run the above SQL query on some of your user ids to see if you also see missing user_actions data and report back?
(Yes, if user A edits user B’s post, there is always a forced edit revision, but that doesn’t mean that if user A edits user B’s post 6 times in 60 seconds, there are 6 revisions and 6 notifications created. There will be only one revision and one notification, as you can see in the above screenshot.)
Are each of these edits more than 5 minutes apart?
Thanks for the comment, Jeff. I can confirm that yes, these edits are more than 5 minutes apart. But even if they weren’t, as long as a single post_revision gets created, shouldn’t there ALWAYS be an accompanying EDIT user_action?
As a side note, I also tried changing the editing grace period to 0 and when I do that, 2 identical post_revisions are created for every change. I don’t know if this is by design or if it’s an unrelated bug.
Digging through our code I think you only get user_action type 11 if you edit someone elses post or trigger a notification regarding the edit in some other way.
Thanks, Sam. That’s what I was expecting, but it’s not what I’ve found (on my site, at least). As you can see from the results of my query, in some cases, user A edits a post by user B (which adds a row in post_revisions), but there is no corresponding row in user_actions (with action_type 11). That is what I don’t understand.
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.
We had an edge case where when a user liked a post by another user and then followed up by editing it we would not notify on the edit.
Additionally I added a safety guard that ensures we notify unconditionally once a day even if it is a repeat editor. (we suppress repeat edit notifications from the same editor for 1 day). This is not configurable at the moment.
