Database error

A database query syntax error has occurred. This may indicate a bug in the software. The last attempted database query was:
(SQL query hidden)
from within function "MediaWikiBagOStuff:_doquery". MySQL returned error "1062: Duplicate entry 'monowikidb2:pcache:idhash:0-1!1!0!0!0!1!0!!en' for key 1 (localhost)".