code: public void addShardStart(TableDefinition tableDef, int shardNumber, Date startDate) {
          assert tableDef.isSharded() && shardNumber > 0;
          addColumn(SpiderService.termsStoreName(tableDef),
                    SHARDS_ROW_KEY,
                    Integer.toString(shardNumber),
                    Utils.toBytes(Long.toString(startDate.getTime())));
      }
docs: Add a column to the "_shards" row for the given shard number and date, indicating
  that this shard is being used. The "_shards" row lives in the table's Terms store
  and uses the format:
  <pre>
  _shards = {{shard 1}:{date 1}, {shard 1}:{date 2}, ...}
  </pre>
  Dates are stored as {@link Date#getTime()} values, converted to strings via
  {@link Long#toString()}.
  
  @param tableDef      {@link TableDefinition} of a sharded table.
  @param shardNumber   Number of a new shard (must be > 0).
  @param startDate     Date that marks the beginning of object timestamp values that
  reside in the shard.