diff options
Diffstat (limited to 'db')
| -rw-r--r-- | db/migrate/20170920032311_fix_reblogs_in_feeds.rb | 84 |
1 files changed, 49 insertions, 35 deletions
diff --git a/db/migrate/20170920032311_fix_reblogs_in_feeds.rb b/db/migrate/20170920032311_fix_reblogs_in_feeds.rb index c813ecd46..439c5fca0 100644 --- a/db/migrate/20170920032311_fix_reblogs_in_feeds.rb +++ b/db/migrate/20170920032311_fix_reblogs_in_feeds.rb @@ -3,48 +3,62 @@ class FixReblogsInFeeds < ActiveRecord::Migration[5.1] redis = Redis.current fm = FeedManager.instance - # find_each is batched on the database side. - User.includes(:account).find_each do |user| - account = user.account + # Old scheme: + # Each user's feed zset had a series of score:value entries, + # where "regular" statuses had the same score and value (their + # ID). Reblogs had a score of the reblogging status' ID, and a + # value of the reblogged status' ID. - # Old scheme: - # Each user's feed zset had a series of score:value entries, - # where "regular" statuses had the same score and value (their - # ID). Reblogs had a score of the reblogging status' ID, and a - # value of the reblogged status' ID. - - # New scheme: - # The feed contains only entries with the same score and value. - # Reblogs result in the reblogging status being added to the - # feed, with an entry in a reblog tracking zset (where the score - # is once again set to the reblogging status' ID, and the value - # is set to the reblogged status' ID). This is safe for Redis' - # float coersion because in this reblog tracking zset, we only - # need the rebloggging status' ID to be able to stop tracking - # entries after they have gotten too far down the feed, which - # does not require an exact value. - - # So, first, we iterate over the user's feed to find any reblogs. - timeline_key = fm.key(:home, account.id) - reblog_key = fm.key(:home, account.id, 'reblogs') - redis.zrange(timeline_key, 0, -1, with_scores: true).each do |entry| - next if entry[0] == entry[1] + # New scheme: + # The feed contains only entries with the same score and value. + # Reblogs result in the reblogging status being added to the + # feed, with an entry in a reblog tracking zset (where the score + # is once again set to the reblogging status' ID, and the value + # is set to the reblogged status' ID). This is safe for Redis' + # float coersion because in this reblog tracking zset, we only + # need the rebloggging status' ID to be able to stop tracking + # entries after they have gotten too far down the feed, which + # does not require an exact value. + + # This process reads all feeds and writes 3 times for each reblogs. + # So we use Lua script to avoid overhead between Ruby and Redis. + script = <<-LUA + local timeline_key = KEYS[1] + local reblog_key = KEYS[2] - # The score and value don't match, so this is a reblog. - # (note that we're transitioning from IDs < 53 bits so we - # don't have to worry about the loss of precision) + -- So, first, we iterate over the user's feed to find any reblogs. + local items = redis.call('zrange', timeline_key, 0, -1, 'withscores') + + for i = 1, #items, 2 do + local reblogged_id = items[i] + local reblogging_id = items[i + 1] + if (reblogged_id ~= reblogging_id) then - reblogged_id, reblogging_id = entry + -- The score and value don't match, so this is a reblog. + -- (note that we're transitioning from IDs < 53 bits so we + -- don't have to worry about the loss of precision) - # Remove the old entry - redis.zrem(timeline_key, reblogged_id) + -- Remove the old entry + redis.call('zrem', timeline_key, reblogged_id) - # Add a new one for the reblogging status - redis.zadd(timeline_key, reblogging_id, reblogging_id) + -- Add a new one for the reblogging status + redis.call('zadd', timeline_key, reblogging_id, reblogging_id) - # Track the fact that this was a reblog - redis.zadd(reblog_key, reblogging_id, reblogged_id) + -- Track the fact that this was a reblog + redis.call('zadd', reblog_key, reblogging_id, reblogged_id) + end end + LUA + script_hash = redis.script(:load, script) + + # find_each is batched on the database side. + User.includes(:account).find_each do |user| + account = user.account + + timeline_key = fm.key(:home, account.id) + reblog_key = fm.key(:home, account.id, 'reblogs') + + redis.evalsha(script_hash, [timeline_key, reblog_key]) end end |