When I'm deleting items on Wikidata too fast (many items within short timeframe), I get a database error. I'm using a "flooder" user group.
A database query error has occurred. This may indicate a bug in the software.
Error: 1213 Deadlock found when trying to get lock; try restarting transaction (10.64.32.28)
See especially the last comment by Adam Shorland (WMDE).