I have a bot account on Wikimedia Commons that—through the setting to add articles I edit and files I upload to my watchlist—inadvertently acquired a watchlist of over 150,000 pages. I was hoping to clear this watchlist and start over so it could be usable, since there seem to be limitations on watchlist size.
However, attempting to clear the watchlist, either using Special:EditWatchlist/raw/clear or Special:EditWatchlist/raw results in a "transaction size" database error: 'To avoid creating high replication lag, this transaction was aborted because the write duration (4.5993978977203) exceeded the 3 second limit. If you are changing many items at once, try doing multiple smaller operations instead.[WbGAXwpAMFUAAB0jkb8AAAAF] 2017-09-07 17:23:25: Fatal exception of type "Wikimedia\Rdbms\DBTransactionSizeError"'
Attempting to load Special:EditWatchlist at all results in a slightly different error—the page spins until it returns a 504 Gateway Timeout Error with no MediaWiki error message.
Because of this, it appears the account is stuck in a limbo, with a watchlist too big to load changes, but also too big to edit down to a usable size.
Possibly related: https://phabricator.wikimedia.org/T171027