presto-main/src/main/java/io/prestosql/sql/planner/optimizations/HashGenerationOptimizer.java/Rewriter/visitSpatialJoin
class Rewriter:        @Override
        public PlanWithProperties visitSpatialJoin(SpatialJoinNode node, HashComputationSet parentPreference)
        {
            PlanWithProperties left = planAndEnforce(node.getLeft(), new HashComputationSet(), true, new HashComputationSet());
            PlanWithProperties right = planAndEnforce(node.getRight(), new HashComputationSet(), true, new HashComputationSet());
            verify(left.getHashSymbols().isEmpty(), "probe side of the spatial join should not include hash symbols");
            verify(right.getHashSymbols().isEmpty(), "build side of the spatial join should not include hash symbols");
            return new PlanWithProperties(
                    replaceChildren(node, ImmutableList.of(left.getNode(), right.getNode())),
                    ImmutableMap.of());
        }