code: public Object generateKey(FieldList record)
      {
          if (record.isQueryRecord())
              return record;      // These can't be shared
          else if ((record.getDatabaseType() & Constants.TABLE_TYPE_MASK) == Constants.UNSHAREABLE_MEMORY)   // Special sharable temp memory file
              return record;      // These can't be shared
          else
              return this.getUniqueFilePath(record);  // These can be shared
      }
docs: Get the unique key used to find this record's physical table in the hash table.
  Query records and UNSHARABLE_MEMORY are not shared, so their key is the record object.
  <p />Note: If the key is a string, it is a unique file path.
  @param The record to generate a unique key for.
  @return The unique object to put in a hash table.