@Override public Prel visitPrel(Prel prel, Void value) throws RuntimeException { SelectionVectorMode[] encodings = prel.getSupportedEncodings(); List<RelNode> children = Lists.newArrayList(); for (Prel child : prel) { child = child.accept(this, null); children.add(convert(encodings, child)); } return (Prel) prel.copy(prel.getTraitSet(), children); }