class FusionIndexUpdater extends FusionIndexBase<IndexUpdater> implements IndexUpdater {

    @Override
    public void process( IndexEntryUpdate<?> update ) throws IndexEntryConflictException
    {
        switch ( update.updateMode() )
        {
        case ADDED:
            instanceSelector.select( slotSelector.selectSlot( update.values(), GROUP_OF ) ).process( update );
            break;
        case CHANGED:
            // Hmm, here's a little conundrum. What if we change from a value that goes into native
            // to a value that goes into fallback, or vice versa? We also don't want to blindly pass
            // all CHANGED updates to both updaters since not all values will work in them.
            IndexUpdater from = instanceSelector.select( slotSelector.selectSlot( update.beforeValues(), GROUP_OF ) );
            IndexUpdater to = instanceSelector.select( slotSelector.selectSlot( update.values(), GROUP_OF ) );
            // There are two cases:
            // - both before/after go into the same updater --> pass update into that updater
            if ( from == to )
            {
                from.process( update );
            }
            // - before go into one and after into the other --> REMOVED from one and ADDED into the other
            else
            {
                from.process( IndexEntryUpdate.remove( update.getEntityId(), update.indexKey(), update.beforeValues() ) );
                to.process( IndexEntryUpdate.add( update.getEntityId(), update.indexKey(), update.values() ) );
            }
            break;
        case REMOVED:
            instanceSelector.select( slotSelector.selectSlot( update.values(), GROUP_OF ) ).process( update );
            break;
        default:
            throw new IllegalArgumentException( "Unknown update mode" );
        }
    }

      FusionIndexUpdater( SlotSelector slotSelector, LazyInstanceSelector<IndexUpdater> instanceSelector );

}