public Void visitGroupByOperator()

in algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/visitors/FDsAndEquivClassesVisitor.java [215:322]
101 lines of code
22 McCabe index (conditional complexity)

    public Void visitGroupByOperator(GroupByOperator op, IOptimizationContext ctx) throws AlgebricksException {
        Map<LogicalVariable, EquivalenceClass> equivalenceClasses = new HashMap<LogicalVariable, EquivalenceClass>();
        List<FunctionalDependency> functionalDependencies = new ArrayList<FunctionalDependency>();
        ctx.putEquivalenceClassMap(op, equivalenceClasses);
        ctx.putFDList(op, functionalDependencies);

        List<FunctionalDependency> inheritedFDs = new ArrayList<FunctionalDependency>();
        for (ILogicalPlan p : op.getNestedPlans()) {
            for (Mutable<ILogicalOperator> r : p.getRoots()) {
                ILogicalOperator op2 = r.getValue();
                equivalenceClasses.putAll(getOrComputeEqClasses(op2, ctx));
                inheritedFDs.addAll(getOrComputeFDs(op2, ctx));
            }
        }

        ILogicalOperator op0 = op.getInputs().get(0).getValue();
        inheritedFDs.addAll(getOrComputeFDs(op0, ctx));
        Map<LogicalVariable, EquivalenceClass> inheritedEcs = getOrComputeEqClasses(op0, ctx);
        for (FunctionalDependency inherited : inheritedFDs) {
            boolean isCoveredByGbyOrDecorVars = true;
            List<LogicalVariable> newHead = new ArrayList<LogicalVariable>(inherited.getHead().size());
            for (LogicalVariable v : inherited.getHead()) {
                LogicalVariable vnew = getNewGbyVar(op, v);
                if (vnew == null) {
                    vnew = getNewDecorVar(op, v);
                    if (vnew == null) {
                        isCoveredByGbyOrDecorVars = false;
                    }
                    break;
                }
                newHead.add(vnew);
            }

            if (isCoveredByGbyOrDecorVars) {
                List<LogicalVariable> newTail = new ArrayList<LogicalVariable>();
                for (LogicalVariable v2 : inherited.getTail()) {
                    LogicalVariable v3 = getNewGbyVar(op, v2);
                    if (v3 != null) {
                        newTail.add(v3);
                    }
                }
                if (!newTail.isEmpty()) {
                    FunctionalDependency newFd = new FunctionalDependency(newHead, newTail);
                    functionalDependencies.add(newFd);
                }
            }
        }

        List<LogicalVariable> premiseGby = new LinkedList<LogicalVariable>();
        List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> gByList = op.getGroupByList();
        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
            premiseGby.add(p.first);
        }

        List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> decorList = op.getDecorList();

        LinkedList<LogicalVariable> conclDecor = new LinkedList<LogicalVariable>();
        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : decorList) {
            conclDecor.add(GroupByOperator.getDecorVariable(p));
        }
        if (!conclDecor.isEmpty()) {
            functionalDependencies.add(new FunctionalDependency(premiseGby, conclDecor));
        }

        Set<LogicalVariable> gbySet = new HashSet<LogicalVariable>();
        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
            ILogicalExpression expr = p.second.getValue();
            if (expr.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
                VariableReferenceExpression v = (VariableReferenceExpression) expr;
                gbySet.add(v.getVariableReference());
            }
        }
        LocalGroupingProperty lgp = new LocalGroupingProperty(gbySet);
        lgp.normalizeGroupingColumns(inheritedEcs, inheritedFDs);
        Set<LogicalVariable> normSet = lgp.getColumnSet();
        List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> newGbyList = new ArrayList<Pair<LogicalVariable, Mutable<ILogicalExpression>>>();
        boolean changed = false;
        for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gByList) {
            ILogicalExpression expr = p.second.getValue();
            if (expr.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
                VariableReferenceExpression varRef = (VariableReferenceExpression) expr;
                LogicalVariable v2 = varRef.getVariableReference();
                EquivalenceClass ec2 = inheritedEcs.get(v2);
                LogicalVariable v3;
                if (ec2 != null && !ec2.representativeIsConst()) {
                    v3 = ec2.getVariableRepresentative();
                } else {
                    v3 = v2;
                }
                if (normSet.contains(v3)) {
                    newGbyList.add(p);
                } else {
                    changed = true;
                    decorList.add(p);
                }
            } else {
                newGbyList.add(p);
            }
        }
        if (changed) {
            AlgebricksConfig.ALGEBRICKS_LOGGER
                    .fine(">>>> Group-by list changed from " + GroupByOperator.veListToString(gByList) + " to "
                            + GroupByOperator.veListToString(newGbyList) + ".\n");
        }
        gByList.clear();
        gByList.addAll(newGbyList);
        return null;
    }