private static Pair pushThroughOp()

in algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushProjectDownRule.java [80:163]
75 lines of code
22 McCabe index (conditional complexity)

    private static Pair<Boolean, Boolean> pushThroughOp(HashSet<LogicalVariable> toPush,
            Mutable<ILogicalOperator> opRef2, ILogicalOperator initialOp, IOptimizationContext context)
                    throws AlgebricksException {
        List<LogicalVariable> initProjectList = new ArrayList<LogicalVariable>(toPush);
        AbstractLogicalOperator op2 = (AbstractLogicalOperator) opRef2.getValue();
        do {
            if (op2.getOperatorTag() == LogicalOperatorTag.EMPTYTUPLESOURCE
                    || op2.getOperatorTag() == LogicalOperatorTag.NESTEDTUPLESOURCE
                    || op2.getOperatorTag() == LogicalOperatorTag.PROJECT
                    || op2.getOperatorTag() == LogicalOperatorTag.REPLICATE
                    || op2.getOperatorTag() == LogicalOperatorTag.UNIONALL) {
                return new Pair<Boolean, Boolean>(false, false);
            }
            if (!op2.isMap()) {
                break;
            }
            LinkedList<LogicalVariable> usedVars = new LinkedList<LogicalVariable>();
            VariableUtilities.getUsedVariables(op2, usedVars);
            toPush.addAll(usedVars);
            LinkedList<LogicalVariable> producedVars = new LinkedList<LogicalVariable>();
            VariableUtilities.getProducedVariables(op2, producedVars);
            toPush.removeAll(producedVars);
            // we assume pipelineable ops. have only one input
            opRef2 = op2.getInputs().get(0);
            op2 = (AbstractLogicalOperator) opRef2.getValue();
        } while (true);

        LinkedList<LogicalVariable> produced2 = new LinkedList<LogicalVariable>();
        VariableUtilities.getProducedVariables(op2, produced2);
        LinkedList<LogicalVariable> used2 = new LinkedList<LogicalVariable>();
        VariableUtilities.getUsedVariables(op2, used2);

        boolean canCommuteProjection = initProjectList.containsAll(toPush) && initProjectList.containsAll(produced2)
                && initProjectList.containsAll(used2);
                // if true, we can get rid of the initial projection

        // get rid of useless decor vars.
        if (!canCommuteProjection && op2.getOperatorTag() == LogicalOperatorTag.GROUP) {
            boolean gbyChanged = false;
            GroupByOperator gby = (GroupByOperator) op2;
            List<Pair<LogicalVariable, Mutable<ILogicalExpression>>> newDecorList = new ArrayList<Pair<LogicalVariable, Mutable<ILogicalExpression>>>();
            for (Pair<LogicalVariable, Mutable<ILogicalExpression>> p : gby.getDecorList()) {
                LogicalVariable decorVar = GroupByOperator.getDecorVariable(p);
                if (!toPush.contains(decorVar)) {
                    used2.remove(decorVar);
                    gbyChanged = true;
                } else {
                    newDecorList.add(p);
                }
            }
            gby.getDecorList().clear();
            gby.getDecorList().addAll(newDecorList);
            if (gbyChanged) {
                context.computeAndSetTypeEnvironmentForOperator(gby);
            }
        }
        used2.clear();
        VariableUtilities.getUsedVariables(op2, used2);

        toPush.addAll(used2); // remember that toPush is a Set
        toPush.removeAll(produced2);

        if (toPush.isEmpty()) {
            return new Pair<Boolean, Boolean>(false, false);
        }

        boolean smthWasPushed = false;
        for (Mutable<ILogicalOperator> c : op2.getInputs()) {
            if (pushNeededProjections(toPush, c, context, initialOp)) {
                smthWasPushed = true;
            }
        }
        if (op2.hasNestedPlans()) {
            AbstractOperatorWithNestedPlans n = (AbstractOperatorWithNestedPlans) op2;
            for (ILogicalPlan p : n.getNestedPlans()) {
                for (Mutable<ILogicalOperator> r : p.getRoots()) {
                    if (pushNeededProjections(toPush, r, context, initialOp)) {
                        smthWasPushed = true;
                    }
                }
            }
        }
        return new Pair<Boolean, Boolean>(smthWasPushed, canCommuteProjection);
    }