Class IntersectionIterator

src/query/expression/IntersectionIterator.java:57–521

This class handles taking a set of queries and their results and iterates over each series in each set with time alignment after computing the intersection of all sets. The iterator performs the following: - calculates the intersection of all queries based on the tags or query tags and optiona

 * @since 2.3
 */
public class IntersectionIterator implements ITimeSyncedIterator, VariableIterator {
  private static final Logger LOG = LoggerFactory.getLogger(IntersectionIterator.class);
  
  /** The queries compiled and fetched from storage */
  private final Map<String, ITimeSyncedIterator> queries;
  
  /** A list of the current values for each series post intersection */
  private final Map<String, ExpressionDataPoint[]> current_values;

  /** A map of the sub query index to their names for intersection computation */
  private final String[] index_to_names;
  
  /** Whether or not to intersect on the query tagks instead of the result set
   * tagks */
  private final boolean intersect_on_query_tagks;
  
  /** Whether or not to include the aggregated tags in the result set */
  private final boolean include_agg_tags;
  
  /** The start/current timestamp for the iterator in ms */
  private long timestamp;
  
  /** Post intersection number of time series */
  private int series_size;
  
  /** The ID of this iterator */
  private final String id;
  
  /** The index of this iterator in a list of iterators */
  private int index;
  
  /**
   * Ctor to create the expression lock-step iterator from a set of query results.
   * If the results map is empty, then the ctor will complete but the results map
   * will be empty and calls to {@link #hasNext()} will always return false.
   * @param results The query results to store
   * @param intersect_on_query_tagks Whether or not to include only the query 
   * specified tags during intersection
   * @param include_agg_tags Whether or not to include aggregated tags during
   * intersection
   * @throws IllegalDataException if, after computing the intersection, no results
   * would be left.
   */
  public IntersectionIterator(final String id, final Map<String, ITimeSyncedIterator> results, 
      final boolean intersect_on_query_tagks, final boolean include_agg_tags) {
    this.id = id;
    this.intersect_on_query_tagks = intersect_on_query_tagks;
    this.include_agg_tags = include_agg_tags;
    timestamp = Long.MAX_VALUE;
    queries = new HashMap<String, ITimeSyncedIterator>(results.size());
    current_values = new HashMap<String, ExpressionDataPoint[]>(results.size());
    index_to_names = new String[results.size()];
    
    int max_series = 0;
    int i = 0;
    for (final Map.Entry<String, ITimeSyncedIterator> entry : results.entrySet()) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Adding iterator " + entry.getValue());