Class TimeSyncedIterator

src/query/expression/TimeSyncedIterator.java:26–248

Holds the results of a sub query (a single metric) and iterates over each resultant series in lock-step for expression evaluation. @since 2.3

 * @since 2.3
 */
public class TimeSyncedIterator implements ITimeSyncedIterator {
  
  /** The name of this sub query given by the user */
  private final String id;
  
  /** The set of tag keys issued with the query */
  private final ByteSet query_tagks;

  /** The data point interfaces fetched from storage */
  private final DataPoints[] dps;
  
  /** The current value used for iterating */
  private final DataPoint[] current_values;
  
  /** References to the MutableDataObjects the ExpressionIterator will read */
  private final ExpressionDataPoint[] emitter_values;
  
  /** A list of the iterators used for fetching the next value */
  private final SeekableView[] iterators;

  /** Set by the ExpressionIterator when it computes the intersection */ 
  private int index;
  
  /** A policy to use for emitting values when a timestamp is missing data */
  private NumericFillPolicy fill_policy;
  
  /**
   * Instantiates an iterator based on the results of a TSSubQuery. 
   * This will setup the emitters so it's safe to call {@link #values()}
   * @param id The name of the query.
   * @param query_tagks The set of tags used in filters on the query.
   * @param dps The data points fetched from storage.
   * @throws IllegalArgumentException if one of the parameters is null or the ID
   * is empty
   */
  public TimeSyncedIterator(final String id, final ByteSet query_tagks, 
      final DataPoints[] dps) {
    if (id == null || id.isEmpty()) {
      throw new IllegalArgumentException("Missing ID string");
    }
    if (dps == null) {
      // it's ok for these to be empty, but they canna be null ya ken?
      throw new IllegalArgumentException("Missing data points");
    }
    this.id = id;
    this.query_tagks = query_tagks;
    this.dps = dps;
    // TODO - load from a default or something
    fill_policy = new NumericFillPolicy(FillPolicy.ZERO);
    current_values = new DataPoint[dps.length];
    emitter_values = new ExpressionDataPoint[dps.length];
    iterators = new SeekableView[dps.length];
    setupEmitters();
  }
  
  /**
   * A copy constructor that loads from an existing iterator.
   * @param iterator The iterator to load from