Change the rules for automatically retiring aliases and implications:
* Retire aliases to tags that are empty, or that are for a general or
artist tag that hasn't received any new posts in the last two years.
* Retire implications from tags that are empty.
* Don't retire aliases or implications for character, copyright, or
meta tags any more, unless the tags are empty.
Stop updating the fav_string attribute on posts. The column still exists
on the table, but is no longer used or updated.
Like the pool_string in 7d503f08, the fav_string was used in the past to
facilitate `fav:X` searches. Posts had a hidden fav_string column that
contained a list of every user who favorited the post. These were
treated like fake hidden tags on the post so that a search for `fav:X`
was treated like a tag search.
The fav_string attribute has been unused for search purposes for a while
now. It was only kept because of technicalities that required
departitioning the favorites table first (340e1008e) before it could be
removed. Basically, removing favorites with `@favorite.destroy` was
slow because Rails always deletes object by ID, but we didn't have an
index on favorites.id, and we couldn't easily add one until the
favorites table was departitioned.
Fixes#4652. See https://github.com/danbooru/danbooru/issues/4652#issuecomment-754993802
for more discussion of issues caused by the fav_string (in short: write
amplification, post table bloat, and favorite inconsistency problems).
Break the hourly/daily/weekly/monthly maintenance tasks down into
individual delayed jobs. This way if one task fails, it won't prevent
other tasks from running. Also, jobs can be run in parallel, and can be
individually retried if they fail.
Change the way BURs are processed. Before, we spawned a background job
for each line of the BUR, then processed each job sequentially. Now, we
process the entire BUR sequentially in a single background job.
This means that:
* BURs are truly sequential now. Before certain things like removing
aliases weren't actually performed in a background job, so they were
performed out-of-order before everything else in the BUR.
* Before, if an alias or implication line failed, then subsequent alias
or implication lines would still be processed. This was because each
alias or implication line was queued as a separate job, so a failure
of one job didn't block another. Now, if any alias or implication
fails, the entire BUR will fail and stop processing after that line.
This may be good or bad, depending on whether we actually need the BUR
to be processed in order or not.
* Before, BURs were processed inside a database transaction (except for the
actual updating of posts). Now they're not. This is because we can't
afford to hold transactions open while processing long-running aliases
or implications. This means that if BUR fails in the middle when it is
initially approved, it will be left in a half-complete state. Before
it would be rolled back and left in a pending state with no changes
performed.
* Before, only one BUR at a time could be processed. If multiple BURs
were approved at the same time, then they would queue up and be
processed one at a time. Now, multiple BURs can be processed at the
same time. This may be undesirable when processing large BURs, or BURs
that must be approved in a specific order.
* Before, large tag category changes could time out. This was because
they weren't actually performed in a background job. Now they are, so
they shouldn't time out.
Don't log mod actions when aliases, implications, or mass updates are
processed.
Originally aliases and implications were logged because they could be
approved outside of a BUR. Mass updates could also be performed by mods
without making a forum request. This is no longer the case.
They were also logged for debugging purposes. This is no longer needed.
This generated a lot of spam in the mod action logs when a large BUR was
approved.
* Add a `rename A -> B` command for bulk update requests.
* Change mass updates to only retag the posts, not to move saved
searches or blacklists.
A tag rename does the same thing an alias does, except it doesn't
create a permanent alias. More precisely, a tag rename:
* Moves the wiki.
* Moves the artist entry.
* Moves saved searches.
* Moves blacklists.
* Merges the wikis, if both tags have wiki pages.
* Merges the artist entries, if both tags have artist pages.
* Fixes links in wiki pages to point to the new tag.
* Retags the posts.
Remove the post update count estimate from BUR show pages. This was
complex, slow, and usually inaccurate since it assumed that requests in
a BUR had no overlap with each other, which usually wasn't the case.
Also fixes a bug where mod actions weren't logged on mass updates.
Creating the mod action silently failed because it was called when
CurrentUser wasn' set.
