code: public IndexFormatVersion getIndexFormatVersion()
     {
        if (indexFormatVersion == null)
        {
           if (getContext().getParentHandler() instanceof SearchIndex)
           {
              SearchIndex parent = (SearchIndex)getContext().getParentHandler();
              if (parent.getIndexFormatVersion().getVersion() < indexRegister.getDefaultIndex().getIndexFormatVersion().getVersion())
              {
                 indexFormatVersion = parent.getIndexFormatVersion();
              }
              else
              {
                 indexFormatVersion = indexRegister.getDefaultIndex().getIndexFormatVersion();
              }
           }
           else
           {
              indexFormatVersion = indexRegister.getDefaultIndex().getIndexFormatVersion();
           }
        }
        return indexFormatVersion;
     }
docs: Returns the index format version that this search index is able to
  support when a query is executed on this index.
  
  @return the index format version for this search index.