format_datetime

This parameter is string-only. In permissive mode, which every query runs in, almost every field arrives as a dynamic, so passing one works because Berserk injects asstring: extract-or-null, the value when it really is a string and null otherwise, so the call yields null (a predicate yields false). A property bag or array is therefore not matched, and tostring() is never applied implicitly — use it explicitly to match a bag's JSON text, keys included. To search the strings inside an object or array, write body.* contains "x" (also has, hasprefix and hassuffix). See String coercion and the asXXX family.