s4 today was doing ~6.5M rps of reads for ~20 minutes, causing database lag and "database locked" errors on attempting to use uploadwizard.
The query at fault looks to be: `UPDATE /* WikiPage::updateCategoryCounts */ `category` SET cat_pages = cat_pages - 1, cat_subcats = cat_subcats - 1 WHERE cat_title = 11`
This should probably instead be `WHERE cat_title = '11'`. This bug is possibly similar to T239877 ?
https://grafana.wikimedia.org/d/000000278/mysql-aggregated?orgId=1&from=1576015480395&to=1576018128623&fullscreen&panelId=8
https://tendril.wikimedia.org/report/slow_queries?host=%5Edb&user=wikiuser&schema=wik&qmode=eq&query=&hours=.5
https://tendril.wikimedia.org/report/slow_queries_checksum?checksum=d7b5c8b8f1f86eee492b22926627f0b2&host=%5Edb&user=wikiuser&schema=wik&hours=.5