public boolean isFullyCoveredBy(ColumnFamily cf, long now)
{
// cf will cover all the requested columns if the range it covers include
// all said columns
CellName first = cf.iterator(ColumnSlice.ALL_COLUMNS_ARRAY).next().name();
CellName last = cf.reverseIterator(ColumnSlice.ALL_COLUMNS_ARRAY).next().name();
return cf.getComparator().compare(first, columns.first()) <= 0
&& cf.getComparator().compare(columns.last(), last) <= 0;
}