Examples with RexShuttle org.apache.calcite.rex.RexShuttle used on opensource projects

Example 21 with RexShuttle

use of org.apache.calcite.rex.RexShuttle in project drill by apache.

the class FindLimit0Visitor method addLimitOnTopOfLeafNodes.

public static DrillRel addLimitOnTopOfLeafNodes(final DrillRel rel) {
    final Pointer<Boolean> isUnsupported = new Pointer<>(false);
    // to visit unsupported functions
    final RexShuttle unsupportedFunctionsVisitor = new RexShuttle() {

        @Override
        public RexNode visitCall(RexCall call) {
            final SqlOperator operator = call.getOperator();
            if (isUnsupportedScalarFunction(operator)) {
                isUnsupported.value = true;
                return call;
            }
            return super.visitCall(call);
        }
    };
    // to visit unsupported operators
    final RelShuttle unsupportedOperationsVisitor = new RelShuttleImpl() {

        @Override
        public RelNode visit(RelNode other) {
            if (other instanceof DrillUnionRelBase) {
                isUnsupported.value = true;
                return other;
            } else if (other instanceof DrillProjectRelBase) {
                if (!isUnsupported.value) {
                    other.accept(unsupportedFunctionsVisitor);
                }
                if (isUnsupported.value) {
                    return other;
                }
            }
            return super.visit(other);
        }
    };
    rel.accept(unsupportedOperationsVisitor);
    if (isUnsupported.value) {
        return rel;
    }
    // to add LIMIT (0) on top of leaf nodes
    final RelShuttle addLimitOnScanVisitor = new RelShuttleImpl() {

        private RelNode addLimitAsParent(RelNode node) {
            final RexBuilder builder = node.getCluster().getRexBuilder();
            final RexLiteral offset = builder.makeExactLiteral(BigDecimal.ZERO);
            final RexLiteral fetch = builder.makeExactLiteral(BigDecimal.ZERO);
            return new DrillLimitRel(node.getCluster(), node.getTraitSet(), node, offset, fetch);
        }

        @Override
        public RelNode visit(LogicalValues values) {
            return addLimitAsParent(values);
        }

        @Override
        public RelNode visit(TableScan scan) {
            return addLimitAsParent(scan);
        }

        @Override
        public RelNode visit(RelNode other) {
            if (other.getInputs().isEmpty()) {
                // leaf operator
                return addLimitAsParent(other);
            }
            return super.visit(other);
        }
    };
    return (DrillRel) rel.accept(addLimitOnScanVisitor);
}