presto-main/src/main/java/io/prestosql/sql/planner/optimizations/IndexJoinOptimizer.java/IndexJoinOptimizer/createIndexJoinWithExpectedOutputs
class IndexJoinOptimizer:        private static PlanNode createIndexJoinWithExpectedOutputs(List<Symbol> expectedOutputs, IndexJoinNode.Type type, PlanNode probe, PlanNode index, List<IndexJoinNode.EquiJoinClause> equiJoinClause, PlanNodeIdAllocator idAllocator)
        {
            PlanNode result = new IndexJoinNode(idAllocator.getNextId(), type, probe, index, equiJoinClause, Optional.empty(), Optional.empty());
            if (!result.getOutputSymbols().equals(expectedOutputs)) {
                result = new ProjectNode(
                        idAllocator.getNextId(),
                        result,
                        Assignments.identity(expectedOutputs));
            }
            return result;
        }