A database query error has occurred. Did you forget to run your application's database schema updater after upgrading? Function: IndexPager::buildQueryInfo (contributions page unfiltered) Error: 0
~1400 errors an hour in logstash; this is by far the main production error right now.
Request of limit of 50000(!) (which MW moderated down to 5000) and timerange of 2005–2017 suggests this is a query from a badly-behaved bot or scraper. The UA used by this client was just an unchanged-from-defaults python-requests/x.y.z. In the future we should find time to heavily ratelimit or block default User-Agents per our own unenforced policy.