import com.liferay.portal.kernel.search.Indexer;
import com.liferay.portal.kernel.search.IndexerRegistryUtil;

out.println("START: " + new Date().toString());
indexer = IndexerRegistryUtil.getIndexer("com.liferay.portlet.journal.model.JournalArticle");

List<Long> structures = new ArrayList<Long>(1);

structures.add(new Long(10805));

indexer.reindexDDMStructures(structures);

out.println("END: " + new Date().toString());