Class ExpressionIterator

src/query/expression/ExpressionIterator.java:67–487

A iterator that applies an expression to the results of multiple sub queries. To use this class: - Instantiate with a valid expression - Call #getVariableNames() and iterate over a set of TSSubQueries and their results. For each query that matches a variable name, call {@link #addResults

 * "missing" data points.
 */
public class ExpressionIterator implements ITimeSyncedIterator {
  private static final Logger LOG = LoggerFactory.getLogger(ExpressionIterator.class);
  
  /** This is only here to to force the shade plugin to include the class in the fat-jar */
  private static final JexlScriptEngineFactory JEXL_FACTORY = null;
  
  /** Docs don't say whether this is thread safe or not. SOME methods are marked
   * as not thread safe, so I assume it's ok to instantiate one of these guys
   * and keep creating scripts from it.
   */
  public final static JexlEngine JEXL_ENGINE = new JexlEngine();
  
  /** 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;
  
  /** List of iterators and their IDs */
  private final Map<String, ITimeSyncedIterator> results;
  
  /** The compiled expression */
  private final Script expression;
  
  /** The context where we'll dump results for processing through the expression */
  private final JexlContext context = new MapContext();
  
  /** A list of unique variable names pulled from the expression */
  private final Set<String> names;
  
  /** The intersection iterator we'll use for processing */
  // TODO - write an interface to allow other set operators, e.g. union, disjoint
  private VariableIterator iterator;

  /** A map of results from the intersection iterator to pass to the expression */
  private Map<String, ExpressionDataPoint[]> iteration_results;
  
  /** The results of processing the expressions */
  private ExpressionDataPoint[] dps;
  
  /** The ID of this iterator */
  private final String id;
  
  /** The index of this iterator in expressions */
  private int index;
  
  /** A fill policy for this expression if data is missing */
  private NumericFillPolicy fill_policy;
  
  /** The set operator to use for joining sets */
  private SetOperator set_operator;
  
  // NOTE - if the query is set to NONE for the aggregation and the query has
  // no tagk filters then we shouldn't set the II's intersect_on_query_tagks
  /**
   * Default Ctor that compiles the expression for use with this iterator.
   * @param id The id of this iterator.