remote exchange (GATHER, SINGLE, [])
    local exchange (GATHER, UNKNOWN, [])
        remote exchange (REPARTITION, ROUND_ROBIN, [])
            final aggregation over (substr)
                local exchange (GATHER, SINGLE, [])
                    remote exchange (REPARTITION, HASH, ["substr"])
                        partial aggregation over (substr)
                            join (LEFT, PARTITIONED):
                                remote exchange (REPARTITION, HASH, ["custkey"])
                                    cross join:
                                        scan customer
                                        local exchange (GATHER, SINGLE, [])
                                            remote exchange (REPLICATE, BROADCAST, [])
                                                final aggregation over ()
                                                    local exchange (GATHER, SINGLE, [])
                                                        remote exchange (GATHER, SINGLE, [])
                                                            partial aggregation over ()
                                                                scan customer
                                final aggregation over (custkey_13)
                                    local exchange (GATHER, SINGLE, [])
                                        remote exchange (REPARTITION, HASH, ["custkey_13"])
                                            partial aggregation over (custkey_13)
                                                scan orders
