Improve account deletion performances further (#15407)

* Delete status records by batches of 50

* Do not precompute values that are only used once

* Do not generate redis events for removal of public toots older than two weeks

* Filter reported toots a priori for polls and status deletion

* Do not process reblogs when cleaning up public timelines

As in Mastodon proper, reblogs don't appear in public TLs

* Clean the deleted account's own feed in one go

* Refactor Account#clean_feed_manager and List#clean_feed_manager

* Delete instead of destroy a few more associations

* Fix preloading

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/lib/feed_manager.rb

@@ -230,6 +230,36 @@ class FeedManager
     end
   end
 
+  # Completely clear multiple feeds at once
+  # @param [Symbol] type
+  # @param [Array<Integer>] ids
+  # @return [void]
+  def clean_feeds!(type, ids)
+    reblogged_id_sets = {}
+
+    redis.pipelined do
+      ids.each do |feed_id|
+        redis.del(key(type, feed_id))
+        reblog_key = key(type, feed_id, 'reblogs')
+        # We collect a future for this: we don't block while getting
+        # it, but we can iterate over it later.
+        reblogged_id_sets[feed_id] = redis.zrange(reblog_key, 0, -1)
+        redis.del(reblog_key)
+      end
+    end
+
+    # Remove all of the reblog tracking keys we just removed the
+    # references to.
+    redis.pipelined do
+      reblogged_id_sets.each do |feed_id, future|
+        future.value.each do |reblogged_id|
+          reblog_set_key = key(type, feed_id, "reblogs:#{reblogged_id}")
+          redis.del(reblog_set_key)
+        end
+      end
+    end
+  end
+
   private
 
   # Trim a feed to maximum size by removing older items