Example Applications in C++

David Fisher

Below are some small example applications.

For each example below, there is assumed to be an Indri index and the path to it is passed in as the first argument on the command line.

Retrieving Field Text

The following example shows a method for retrieving field text for the title and any "person" named entities in an Indri index. This example assumes that an Indri index has been built with "title" and "person" tagged as fields at the time the index was built. It also assumes that the path to the index is the first argument to the program.

  #include <vector>
  #include "indri/Repository.hpp"

  // a global repository object for our index
  indri::collection::Repository repository;

  using namespace indri::api;

  void getFieldText(int documentID, std::string field) {
    // get the index from the repository
    // in our case it will be the first index
    indri::collection::Repository::index_state repIndexState = repository.indexes();
    indri::index::Index *thisIndex=(*repIndexState)[0];

    // get the field ID
    int fieldID=thisIndex->field(field);

    // is this a valid field? If not, exit
    if (fieldID < 1) { return; }

    // retrieve the document vector for this document
    const indri::index::TermList *termList=thisIndex->termList(documentID);

    // ensure we have a valid term list!
    if (!termList) { return; }

    // get the vector of fields
    indri::utility::greedy_vector< indri::index::FieldExtent > fieldVec=termList->fields();

    // go through the fields (create an iterator)
    indri::utility::greedy_vector< indri::index::FieldExtent >::iterator fIter=fieldVec.begin();
    while (fIter!=fieldVec.end()) {
      // does the ID of this field extent match our field ID?
      if ((*fIter).id==fieldID) {
        // yes! We can print out the text here
        int beginTerm=(*fIter).begin;
        int endTerm=(*fIter).end;

        // note that the text is inclusive of the beginning
        // but exclusive of the ending
        for (int t=beginTerm; t < endTerm; t++) {
          // get this term ID
          int thisTermID=termList->terms()[t];
          // convert the term ID to its string representation
          cout << thisIndex->term(thisTermID) << " ";
        }
        cout << endl;
      }

      // increment the iterator
      fIter++;
    }

    // destroy the term list object
    delete termList;
    termList=NULL;
  }

 void main(int argc, char *argv[]) {
   // we assume the index path is the first argument and the query is second
   char *indexPath=argv[1];

   // open our repository object (read-only!!)
   repository.openRead(indexPath);

   // retrieve the title field for document 5
   getFieldText(5, "title");

   // retrieve any person fields for document 5
   getFieldText(5, "person");

   // close the repository...
   repository.close();
 }

Getting Snippet Text for Query Results

This example takes a path to the index and a query as the two arguments to it. It opens the index, runs the query, and then prints out a two-column listing consisting of the document ID and the snippet of text that matched on the query.

 #include <vector>
 #include "indri/QueryEnvironment.hpp"
 #include "indri/SnippetBuilder.hpp"

 using namespace indri::api;

 void main(int argc, char *argv[]) {
   // we assume the index path is the first argument and the query is second
   char *indexPath=argv[1];
   char *query=argv[2];

   // our builder object - false in the constructor means no HTML output.
   SnippetBuilder builder(false);

   // create a query environment
   QueryEnvironment indriEnvironment;

   // open the index
   indriEnvironment.addIndex(indexPath);

   // run the query, max of 1000 results
   QueryAnnotation *results=indriEnvironment.runAnnotatedQuery(query, 1000);

   // extract the results as a vector of ScoredExtentResult items
   std::vector<indri::api::ScoredExtentResult> resultVector=results->getResults();

   // get the number of results
   int totalNumResults=resultVector.size();

   // get the parsed documents for the results
   std::vector<ParsedDocument*> parsedDocs=indriEnvironment.documents(resultVector);

   // for each result, print out the document ID and the snippet...
   for (int i=0; i < totalNumResults; i++) {
     // get the document ID
     int thisResultDocID=resultVector[i].document;

     // get this document's parsed doc representation
     ParsedDocument* parsedDoc=parsedDocs[i];

     // print the document ID and the snippet
     cout << thisResultDocID << "\t";
     cout << builder.build(thisResultDocID, parsedDoc, results) << "\n";
   }

  // note that we do not need to explicitly delete the
  // QueryEnvironment object here to close the index. It will
  // automatically be removed when it goes out of scope.
 }

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