-- { echoOn }

explain pipeline select * from (select * from numbers(1e8) group by number) group by number;
(Expression)
ExpressionTransform × 16
  (Aggregating)
  Resize 16 → 16
    AggregatingTransform × 16
      StrictResize 16 → 16
        (Expression)
        ExpressionTransform × 16
          (Aggregating)
          Resize 1 → 16
            AggregatingTransform
              (Expression)
              ExpressionTransform
                (ReadFromStorage)
                Limit
                  Numbers 0 → 1
explain pipeline select * from (select * from numbers_mt(1e8) group by number) group by number;
(Expression)
ExpressionTransform × 16
  (Aggregating)
  Resize 16 → 16
    AggregatingTransform × 16
      StrictResize 16 → 16
        (Expression)
        ExpressionTransform × 16
          (Aggregating)
          Resize 16 → 16
            AggregatingTransform × 16
              (Expression)
              ExpressionTransform × 16
                (ReadFromStorage)
                NumbersMt × 16 0 → 1
explain pipeline select * from (select * from numbers_mt(1e8) group by number) order by number;
(Expression)
ExpressionTransform
  (Sorting)
  MergingSortedTransform 16 → 1
    MergeSortingTransform × 16
      LimitsCheckingTransform × 16
        PartialSortingTransform × 16
          (Expression)
          ExpressionTransform × 16
            (Aggregating)
            Resize 16 → 16
              AggregatingTransform × 16
                (Expression)
                ExpressionTransform × 16
                  (ReadFromStorage)
                  NumbersMt × 16 0 → 1
explain pipeline select number from remote('127.0.0.{1,2,3}', system, numbers_mt) group by number settings distributed_aggregation_memory_efficient = 1;
(Expression)
ExpressionTransform × 16
  (MergingAggregated)
  Resize 1 → 16
    SortingAggregatedTransform 16 → 1
      MergingAggregatedBucketTransform × 16
        Resize 1 → 16
          GroupingAggregatedTransform 3 → 1
            (Union)
              (Aggregating)
              Resize 16 → 1
                AggregatingTransform × 16
                  (Expression)
                  ExpressionTransform × 16
                    (ReadFromStorage)
                    Numbers × 16 0 → 1
              (ReadFromRemote)
explain pipeline select number from remote('127.0.0.{1,2,3}', system, numbers_mt) group by number settings distributed_aggregation_memory_efficient = 0;
(Expression)
ExpressionTransform × 16
  (MergingAggregated)
  Resize 1 → 16
    MergingAggregatedTransform
      Resize 18 → 1
        (Union)
          (Aggregating)
          Resize 16 → 16
            AggregatingTransform × 16
              (Expression)
              ExpressionTransform × 16
                (ReadFromStorage)
                Numbers × 16 0 → 1
          (ReadFromRemote)
-- { echoOn }

explain pipeline SELECT k1, k3, sum(value) v FROM remote('127.0.0.{1,2}', currentDatabase(), proj_agg_02343) GROUP BY k1, k3 SETTINGS distributed_aggregation_memory_efficient = 0;
(Expression)
ExpressionTransform × 16
  (MergingAggregated)
  Resize 1 → 16
    MergingAggregatedTransform
      Resize 2 → 1
        (Union)
          (ReadFromStorage)
          AggregatingTransform
            ExpressionTransform
              MergeTreeInOrder 0 → 1
          (ReadFromRemote)
explain pipeline SELECT k1, k3, sum(value) v FROM remote('127.0.0.{1,2}', currentDatabase(), proj_agg_02343) GROUP BY k1, k3 SETTINGS distributed_aggregation_memory_efficient = 1;
(Expression)
ExpressionTransform × 16
  (MergingAggregated)
  Resize 1 → 16
    SortingAggregatedTransform 16 → 1
      MergingAggregatedBucketTransform × 16
        Resize 1 → 16
          GroupingAggregatedTransform 2 → 1
            (Union)
              (ReadFromStorage)
              AggregatingTransform
                ExpressionTransform
                  MergeTreeInOrder 0 → 1
              (ReadFromRemote)
-- { echoOn }

explain pipeline select a from remote('127.0.0.{1,2}', currentDatabase(), dist_t) group by a settings max_threads = 2, distributed_aggregation_memory_efficient = 1;
(Expression)
ExpressionTransform × 2
  (MergingAggregated)
  Resize 1 → 2
    SortingAggregatedTransform 2 → 1
      MergingAggregatedBucketTransform × 2
        Resize 1 → 2
          GroupingAggregatedTransform 2 → 1
            (Union)
              (MergingAggregated)
              SortingAggregatedTransform 2 → 1
                MergingAggregatedBucketTransform × 2
                  Resize 1 → 2
                    GroupingAggregatedTransform 2 → 1
                      (Union)
                        (Aggregating)
                        Resize 2 → 1
                          AggregatingTransform × 2
                            StrictResize 2 → 2
                              (Expression)
                              ExpressionTransform × 2
                                (ReadFromMergeTree)
                                MergeTreeThread × 2 0 → 1
                        (ReadFromRemote)
              (ReadFromRemote)