code: @Override
      protected boolean isIndexing(CmsResource res) {
  
          if ((res != null) && (getSources() != null)) {
              I_CmsDocumentFactory documentFactory = OpenCms.getSearchManager().getDocumentFactory(res);
              for (CmsSearchIndexSource source : getSources()) {
                  if (source.isIndexing(res.getRootPath(), CmsSolrDocumentContainerPage.TYPE_CONTAINERPAGE_SOLR)
                      || source.isIndexing(res.getRootPath(), CmsSolrDocumentXmlContent.TYPE_XMLCONTENT_SOLR)
                      || ((documentFactory != null) && source.isIndexing(res.getRootPath(), documentFactory.getName()))) {
                      return true;
                  }
              }
          }
          return false;
      }
docs: Checks if the given resource should be indexed by this index or not.<p>
  
  @param res the resource candidate
  
  @return <code>true</code> if the given resource should be indexed or <code>false</code> if not