code: public synchronized void verifyShard(TableDefinition tableDef, int shardNumber) {
          assert tableDef != null;
          assert tableDef.isSharded();
          assert shardNumber > 0;
          
          Map<String, Map<Integer, Date>> tableMap = m_appShardMap.get(tableDef.getAppDef().getAppName());
          if (tableMap != null) {
              Map<Integer, Date> shardMap = tableMap.get(tableDef.getTableName());
              if (shardMap != null) {
                  if (shardMap.containsKey(shardNumber)) {
                      return;
                  }
              }
          }
          
          // Unknown app/table/shard number, so start it.
          Date shardDate = tableDef.computeShardStart(shardNumber);
          addShardStart(tableDef, shardNumber, shardDate);
      }
docs: Verify that the shard with the given number has been registered for the given table.
  If it hasn't, the shard's starting date is computed, the shard is registered in the
  _shards row, and the start date is cached.
  
  @param tableDef      TableDefinition of a sharded table.
  @param shardNumber   Shard number (must be > 0).