A scheduled job runs `Post.rebake_old` with a limit of 80 which does a
look up for the latest posts that have not been baked to the latest
version. Before this commit, the query would run using the primary key's
index and does a reverse scan. However the query performance quicky
becomes bad as more and more of the latest posts have been baked to the
latest version.
In certain edge cases, the message bus won't send the message to the
user about the updated review count and it can go out of sync.
This patch synchronizes the review count every time:
1. The user visits the "Needs Review" page
2. Every time the user performs an action
Previously we tried using a sub-query which has some terrible performance
implications, by adding 1 extra query we can eliminate the PG issue
A join to user_stats also is prone to the same slowdown
restructure query so it avoids ORs
It appears postgres is picking suboptimal indexes if too many ORs exist
despite how trivial the condition is.
This bypasses conditional in the query and evals them upfront.
On meta for my user this made a 10x perf difference.
This boils down to either having `OR u.admin` or not having `OR u.admin` in
the query.
Note, to avoid race conditions we are setting last_unread to 10 minutes ago
if there is nothing unread.
This is safer in case of in progress transactions
we don't want to lose unread for any window of time.
This optimisation avoids large scans joining the topics table with the
topic_users table.
Previously when a user carried a lot of read state we would have to join
the entire read state with the topics table. This operation would slow down
home page and every topic page. The more read state you accumulated the
larger the impact.
The optimisation helps people who clean up unread, however if you carry
unread from years ago it will only have minimal impact.
A new checkbox has been added to the Tags tab of the category settings modal
which is used when some tags and/or tag groups are restricted to the category,
and all other unrestricted tags should also be allowed.
Default is the same as the previous behaviour: only allow the specified set of
tags and tag groups in the category.
Sometimes sidekiq is so fast that it starts jobs before transactions
have comitted. This patch moves the message bus stuff until after things
have comitted.
