The ORDER BY timestamp on the DMs Username History endpoint was causing
SQLite to do a full table scan by timestamp instead of indexing on
channel ID. So, instead, we fetch the distinct channel IDs for the
current user and add them to an IN clause on the main query (instead of
a LIKE clause), which causes the index to use the channel_id instead of
timestamp. This may improve CPU performance and speed on this endpoint.
Noah Petherbridge
89dd40f77f