OOM caused by large tombstone warning.

        if (respectTombstoneThresholds() && columnCounter.ignored() > DatabaseDescriptor.getTombstoneWarnThreshold())
        {
            StringBuilder sb = new StringBuilder();
            CellNameType type = container.metadata().comparator;
            for (ColumnSlice sl : slices)
            {
                assert sl != null;

                sb.append('[');
                sb.append(type.getString(sl.start));
                sb.append('-');
                sb.append(type.getString(sl.finish));
                sb.append(']');
            }

            logger.warn("Read {} live and {} tombstoned cells in {}.{} (see tombstone_warn_threshold). {} columns was requested, slices={}, delInfo={}",
                        columnCounter.live(), columnCounter.ignored(), container.metadata().ksName, container.metadata().cfName, count, sb, container.deletionInfo());
        }