presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/ExtractSpatialJoins.java/ExtractSpatialJoins/addProjection
class ExtractSpatialJoins:    private static PlanNode addProjection(Context context, PlanNode node, Symbol symbol, Expression expression)
    {
        Assignments.Builder projections = Assignments.builder();
        for (Symbol outputSymbol : node.getOutputSymbols()) {
            projections.putIdentity(outputSymbol);
        }

        projections.put(symbol, expression);
        return new ProjectNode(context.getIdAllocator().getNextId(), node, projections.build());
    }