Exemple #1
0
  /**
   * create new Local rearrange by cloning existing rearrange and add plan for projecting the key
   *
   * @param rearrange
   * @return
   * @throws PlanException
   * @throws CloneNotSupportedException
   */
  private static POLocalRearrange getNewRearrange(POLocalRearrange rearrange)
      throws PlanException, CloneNotSupportedException {
    POLocalRearrange newRearrange = rearrange.clone();

    // Set the projection to be the key
    PhysicalPlan newPlan = new PhysicalPlan();
    String scope = newRearrange.getOperatorKey().scope;
    POProject proj =
        new POProject(
            new OperatorKey(scope, NodeIdGenerator.getGenerator().getNextNodeId(scope)), -1, 0);
    proj.setResultType(newRearrange.getKeyType());
    newPlan.add(proj);

    List<PhysicalPlan> plans = new ArrayList<PhysicalPlan>(1);
    plans.add(newPlan);
    newRearrange.setPlansFromCombiner(plans);

    return newRearrange;
  }
Exemple #2
0
  /**
   * Algebraic functions and distinct in nested plan of a foreach are partially computed in the map
   * and combine phase. A new foreach statement with initial and intermediate forms of algebraic
   * functions are added to map and combine plans respectively.
   *
   * <p>If bag portion of group-by result is projected or a non algebraic expression/udf has bag as
   * input, combiner will not be used. This is because the use of combiner in such case is likely to
   * degrade performance as there will not be much reduction in data size in combine stage to offset
   * the cost of the additional number of times (de)serialization is done.
   *
   * <p>Major areas for enhancement: 1. use of combiner in cogroup 2. queries with order-by, limit
   * or sort in a nested foreach after group-by 3. case where group-by is followed by filter that
   * has algebraic expression
   */
  public static void addCombiner(
      PhysicalPlan mapPlan,
      PhysicalPlan reducePlan,
      PhysicalPlan combinePlan,
      CompilationMessageCollector messageCollector,
      boolean doMapAgg)
      throws VisitorException {

    // part one - check if this MR job represents a group-by + foreach. Find
    // the POLocalRearrange in the map. I'll need it later.
    List<PhysicalOperator> mapLeaves = mapPlan.getLeaves();
    if (mapLeaves == null || mapLeaves.size() != 1) {
      messageCollector.collect(
          "Expected map to have single leaf", MessageType.Warning, PigWarning.MULTI_LEAF_MAP);
      return;
    }
    PhysicalOperator mapLeaf = mapLeaves.get(0);
    if (!(mapLeaf instanceof POLocalRearrange)) {
      return;
    }
    POLocalRearrange rearrange = (POLocalRearrange) mapLeaf;

    List<PhysicalOperator> reduceRoots = reducePlan.getRoots();
    if (reduceRoots.size() != 1) {
      messageCollector.collect(
          "Expected reduce to have single root", MessageType.Warning, PigWarning.MULTI_ROOT_REDUCE);
      return;
    }

    // I expect that the first root should always be a POPackage. If not, I
    // don't know what's going on, so I'm out of here.
    PhysicalOperator root = reduceRoots.get(0);
    if (!(root instanceof POPackage)) {
      messageCollector.collect(
          "Expected reduce root to be a POPackage",
          MessageType.Warning,
          PigWarning.NON_PACKAGE_REDUCE_PLAN_ROOT);
      return;
    }
    POPackage pack = (POPackage) root;

    List<PhysicalOperator> packSuccessors = reducePlan.getSuccessors(root);
    if (packSuccessors == null || packSuccessors.size() != 1) {
      return;
    }
    PhysicalOperator successor = packSuccessors.get(0);

    if (successor instanceof POLimit) {
      // POLimit is acceptable, as long has it has a single foreach as
      // successor
      List<PhysicalOperator> limitSucs = reducePlan.getSuccessors(successor);
      if (limitSucs != null && limitSucs.size() == 1 && limitSucs.get(0) instanceof POForEach) {
        // the code below will now further examine the foreach
        successor = limitSucs.get(0);
      }
    }
    if (successor instanceof POForEach) {
      POForEach foreach = (POForEach) successor;
      List<PhysicalPlan> feInners = foreach.getInputPlans();

      // find algebraic operators and also check if the foreach statement
      // is suitable for combiner use
      List<Pair<PhysicalOperator, PhysicalPlan>> algebraicOps = findAlgebraicOps(feInners);
      if (algebraicOps == null || algebraicOps.size() == 0) {
        // the plan is not combinable or there is nothing to combine
        // we're done
        return;
      }
      if (combinePlan != null && combinePlan.getRoots().size() != 0) {
        messageCollector.collect(
            "Wasn't expecting to find anything already " + "in the combiner!",
            MessageType.Warning,
            PigWarning.NON_EMPTY_COMBINE_PLAN);
        return;
      }

      LOG.info("Choosing to move algebraic foreach to combiner");
      try {
        // replace PODistinct->Project[*] with distinct udf (which is Algebraic)
        for (Pair<PhysicalOperator, PhysicalPlan> op2plan : algebraicOps) {
          if (!(op2plan.first instanceof PODistinct)) {
            continue;
          }
          DistinctPatcher distinctPatcher = new DistinctPatcher(op2plan.second);
          distinctPatcher.visit();
          if (distinctPatcher.getDistinct() == null) {
            int errCode = 2073;
            String msg =
                "Problem with replacing distinct operator with distinct built-in function.";
            throw new PlanException(msg, errCode, PigException.BUG);
          }
          op2plan.first = distinctPatcher.getDistinct();
        }

        // create new map foreach
        POForEach mfe = createForEachWithGrpProj(foreach, rearrange.getKeyType());
        Map<PhysicalOperator, Integer> op2newpos = Maps.newHashMap();
        Integer pos = 1;
        // create plan for each algebraic udf and add as inner plan in map-foreach
        for (Pair<PhysicalOperator, PhysicalPlan> op2plan : algebraicOps) {
          PhysicalPlan udfPlan = createPlanWithPredecessors(op2plan.first, op2plan.second);
          mfe.addInputPlan(udfPlan, false);
          op2newpos.put(op2plan.first, pos++);
        }
        changeFunc(mfe, POUserFunc.INITIAL);

        // since we will only be creating SingleTupleBag as input to
        // the map foreach, we should flag the POProjects in the map
        // foreach inner plans to also use SingleTupleBag
        for (PhysicalPlan mpl : mfe.getInputPlans()) {
          try {
            new fixMapProjects(mpl).visit();
          } catch (VisitorException e) {
            int errCode = 2089;
            String msg = "Unable to flag project operator to use single tuple bag.";
            throw new PlanException(msg, errCode, PigException.BUG, e);
          }
        }

        // create new combine foreach
        POForEach cfe = createForEachWithGrpProj(foreach, rearrange.getKeyType());
        // add algebraic functions with appropriate projection
        addAlgebraicFuncToCombineFE(cfe, op2newpos);
        changeFunc(cfe, POUserFunc.INTERMEDIATE);

        // fix projection and function time for algebraic functions in reduce foreach
        for (Pair<PhysicalOperator, PhysicalPlan> op2plan : algebraicOps) {
          setProjectInput(op2plan.first, op2plan.second, op2newpos.get(op2plan.first));
          byte resultType = op2plan.first.getResultType();
          ((POUserFunc) op2plan.first).setAlgebraicFunction(POUserFunc.FINAL);
          op2plan.first.setResultType(resultType);
        }

        // we have modified the foreach inner plans - so set them again
        // for the foreach so that foreach can do any re-initialization
        // around them.
        // FIXME - this is a necessary evil right now because the leaves
        // are explicitly stored in the POForeach as a list rather than
        // computed each time at run time from the plans for
        // optimization. Do we want to have the Foreach compute the
        // leaves each time and have Java optimize it (will Java
        // optimize?)?
        mfe.setInputPlans(mfe.getInputPlans());
        cfe.setInputPlans(cfe.getInputPlans());
        foreach.setInputPlans(foreach.getInputPlans());

        // tell POCombinerPackage which fields need projected and which
        // placed in bags. First field is simple project rest need to go
        // into bags
        int numFields = algebraicOps.size() + 1; // algebraic funcs + group key
        boolean[] bags = new boolean[numFields];
        bags[0] = false;
        for (int i = 1; i < numFields; i++) {
          bags[i] = true;
        }

        // Use the POCombiner package in the combine plan
        // as it needs to act differently than the regular
        // package operator.
        CombinerPackager pkgr = new CombinerPackager(pack.getPkgr(), bags);
        POPackage combinePack = pack.clone();
        combinePack.setPkgr(pkgr);
        combinePack.setParentPlan(null);

        combinePlan.add(combinePack);
        combinePlan.add(cfe);
        combinePlan.connect(combinePack, cfe);

        // No need to connect projections in cfe to cp, because
        // PigCombiner directly attaches output from package to
        // root of remaining plan.

        POLocalRearrange mlr = getNewRearrange(rearrange);
        POPartialAgg mapAgg = null;
        if (doMapAgg) {
          mapAgg = createPartialAgg(cfe);
        }

        // A specialized local rearrange operator will replace
        // the normal local rearrange in the map plan. This behaves
        // like the regular local rearrange in the getNext()
        // as far as getting its input and constructing the
        // "key" out of the input. It then returns a tuple with
        // two fields - the key in the first position and the
        // "value" inside a bag in the second position. This output
        // format resembles the format out of a Package. This output
        // will feed to the map foreach which expects this format.
        // If the key field isn't in the project of the combiner or map foreach,
        // it is added to the end (This is required so that we can
        // set up the inner plan of the new Local Rearrange leaf in the map
        // and combine plan to contain just the project of the key).
        patchUpMap(mapPlan, getPreCombinerLR(rearrange), mfe, mapAgg, mlr);
        POLocalRearrange clr = getNewRearrange(rearrange);
        clr.setParentPlan(null);
        combinePlan.add(clr);
        combinePlan.connect(cfe, clr);

        // Change the package operator in the reduce plan to
        // be the POCombiner package, as it needs to act
        // differently than the regular package operator.
        pack.setPkgr(pkgr.clone());
      } catch (Exception e) {
        int errCode = 2018;
        String msg = "Internal error. Unable to introduce the combiner for optimization.";
        throw new OptimizerException(msg, errCode, PigException.BUG, e);
      }
    }
  }
 @Override
 public void visitLocalRearrange(POLocalRearrange lr) throws VisitorException {
   this.mro.mapKeyType = lr.getKeyType();
   foundKeyType = true;
 }