Returns the latest things done in public, newest first, FEED_MAX at most: the public dumps posted and playlists created, the comments and upvotes on public dumps, and who joined. A dump has one comment event and one upvote event at most, its latest, so that a thread or a popular dump doesn't fill the feed.

Each part reads its FEED_MAX latest, which is all the whole may keep of it. The comments and the upvotes are grouped by dump first, and with MAX() SQLite fills a group's other columns from the row that holds the maximum: the latest comment's author and id, the latest voter.