presto-main/src/main/java/io/prestosql/sql/planner/DistributedExecutionPlanner.java/Visitor/visitFilter
class Visitor:        @Override
        public Map<PlanNodeId, SplitSource> visitFilter(FilterNode node, Void context)
        {
            if (node.getSource() instanceof TableScanNode) {
                TableScanNode scan = (TableScanNode) node.getSource();
                return visitScanAndFilter(scan, Optional.of(node));
            }

            return node.getSource().accept(this, context);
        }