static EffectiveMeta asFloorKey(final long effectiveMs) {
        // Use Long.MAX_VALUE so that the floor() when used with TIME_THEN_ID_COMPARATOR
        // will return the item with an effectiveMs equal to the passed effectiveMs
        return new EffectiveMeta(Long.MAX_VALUE, DUMMY, DUMMY, effectiveMs);
    }
Only to be used as a threshold in {@link NavigableSet#floor(Object)} navigation
where we only care about the effectiveMs.
stroom-meta/stroom-meta-api/src/main/java/stroom/meta/api/EffectiveMeta.java