Returns an always-true ExtraFilter that is textually unique per tag — every tag
yields a distinct cache fingerprint (Filter is part of the fingerprint) while
matching the same rows. This lets each check start from a guaranteed-cold cache
entry without mutating any data.
Returns an always-true ExtraFilter that is textually unique per tag — every tag yields a distinct cache fingerprint (Filter is part of the fingerprint) while matching the same rows. This lets each check start from a guaranteed-cold cache entry without mutating any data.