Ejemplo n.º 1
0
 /**
  * Returns the name of the used query expansion model.
  *
  * @return String the name of the used query expansion model.
  */
 public String getInfo() {
   if (QEModel != null) return QEModel.getInfo();
   return "";
 }
Ejemplo n.º 2
0
  /**
   * Runs the actual query expansion
   *
   * @see
   *     org.terrier.querying.PostProcess#process(org.terrier.querying.Manager,org.terrier.querying.SearchRequest)
   */
  public void process(Manager manager, SearchRequest q) {
    Index index = getIndex(manager);
    lastIndex = index;
    documentIndex = index.getDocumentIndex();
    invertedIndex = index.getInvertedIndex();
    lexicon = index.getLexicon();
    collStats = index.getCollectionStatistics();
    directIndex = index.getDirectIndex();
    metaIndex = index.getMetaIndex();
    if (directIndex == null) {
      logger.error("This index does not have a direct index. Query expansion disabled!!");
      return;
    }
    logger.debug("Starting query expansion post-processing.");
    // get the query expansion model to use
    String qeModel = q.getControl("qemodel");
    if (qeModel == null || qeModel.length() == 0) {
      logger.warn(
          "qemodel control not set for QueryExpansion" + " post process. Using default model Bo1");
      qeModel = "Bo1";
    }
    setQueryExpansionModel(getQueryExpansionModel(qeModel));
    if (logger.isDebugEnabled()) {
      logger.info("query expansion model: " + QEModel.getInfo());
    }
    MatchingQueryTerms queryTerms = ((Request) q).getMatchingQueryTerms();
    if (queryTerms == null) {
      logger.warn("No query terms for this query. Skipping QE");
      return;
    }
    // get the expanded query terms
    try {
      expandQuery(queryTerms, (Request) q);
    } catch (IOException ioe) {
      logger.error("IOException while expanding query, skipping QE", ioe);
      return;
    }
    if (logger.isDebugEnabled()) {
      logger.info("query length after expansion: " + queryTerms.length());
      logger.info("Expanded query: ");
    }
    final String[] newQueryTerms = queryTerms.getTerms();
    StringBuilder newQuery = new StringBuilder();
    for (int i = 0; i < newQueryTerms.length; i++) {
      try {
        if (logger.isDebugEnabled()) {
          logger.info(
              (i + 1)
                  + ": "
                  + newQueryTerms[i]
                  + ", normalisedFrequency: "
                  + Rounding.toString(queryTerms.getTermWeight(newQueryTerms[i]), 4));
        }
        newQuery.append(newQueryTerms[i]);
        newQuery.append('^');
        newQuery.append(Rounding.toString(queryTerms.getTermWeight(newQueryTerms[i]), 9));
        newQuery.append(' ');
      } catch (NullPointerException npe) {
        logger.error("Nullpointer exception occured in Query Expansion dumping of new Query", npe);
      }
    }

    logger.debug("NEWQUERY " + q.getQueryID() + " " + newQuery.toString());
    lastExpandedQuery = newQuery.toString();
    q.setControl("QE.ExpandedQuery", newQuery.toString());
    final boolean no2ndPass =
        Boolean.parseBoolean(ApplicationSetup.getProperty("qe.no.2nd.matching", "false"));
    if (no2ndPass) {
      return;
    }

    // run retrieval process again for the expanded query
    logger.info("Accessing inverted file for expanded query " + q.getQueryID());
    manager.runMatching(q);
  }