First reported in https://meta.discourse.org/t/-/202482/19
There are two optimizations being applied here:
1. Fetch a user's group ids in a seperate query instead of including it
as a sub-query. When I tried a subquery, the query plan becomes very
inefficient.
1. Join against the `topic_allowed_users` and `topic_allowed_groups`
table instead of doing an IN against a subquery where we UNION the
`topic_id`s from the two tables. From my profiling, this enables PG to
do a backwards index scan on the `index_topics_on_timestamps_private`
index.
This commit fixes a bug where listing all messages was incorrectly
excluding topics if a topic has been archived by a group even if the
user did not belong to the group.
This commit also fixes another bug where dismissing private messages
selectively was subjected to the default limit of 30.
ddb458343d