Split traits of ITransformingStep to DataStreamTraits and TransformTraits.

src/Processors/QueryPlan/AddingDelayedSourceStep.cpp

@@ -4,15 +4,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
-        .preserves_distinct_columns = false,
-        .returns_single_stream = false,
-        .preserves_number_of_streams = false,
-        .preserves_number_of_rows = false, /// New rows are added from delayed stream
-        .preserves_sorting = false,
+        {
+            .preserves_distinct_columns = false,
+            .returns_single_stream = false,
+            .preserves_number_of_streams = false,
+            .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = false, /// New rows are added from delayed stream
+        }
     };
 }
 

src/Processors/QueryPlan/AggregatingStep.cpp

@@ -7,15 +7,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = false, /// Actually, we may check that distinct names are in aggregation keys
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = false,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/ConvertingStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = true,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = true,
+        }
     };
 }
 

src/Processors/QueryPlan/CreatingSetsStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = true,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = true,
+        }
     };
 }
 

src/Processors/QueryPlan/CubeStep.cpp

@@ -5,15 +5,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = false,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = false,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/DistinctStep.cpp

@@ -16,15 +16,19 @@ static bool checkColumnsAlreadyDistinct(const Names & columns, const NameSet & d
     return columns_already_distinct;
 }
 
-static ITransformingStep::DataStreamTraits getTraits(bool pre_distinct, bool already_distinct_columns)
+static ITransformingStep::Traits getTraits(bool pre_distinct, bool already_distinct_columns)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = already_distinct_columns, /// Will be calculated separately otherwise
             .returns_single_stream = !pre_distinct && !already_distinct_columns,
             .preserves_number_of_streams = pre_distinct || already_distinct_columns,
-            .preserves_number_of_rows = false,
             .preserves_sorting = true, /// Sorting is preserved indeed because of implementation.
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/ExpressionStep.cpp

@@ -8,15 +8,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(const ExpressionActionsPtr & expression)
+static ITransformingStep::Traits getTraits(const ExpressionActionsPtr & expression)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = !expression->hasJoinOrArrayJoin(),
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = !expression->hasJoinOrArrayJoin(),
             .preserves_sorting = !expression->hasJoinOrArrayJoin(),
+        },
+        {
+            .preserves_number_of_rows = !expression->hasJoinOrArrayJoin(),
+        }
     };
 }
 

src/Processors/QueryPlan/ExtremesStep.cpp

@@ -4,15 +4,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = true,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = true,
+        }
     };
 }
 

src/Processors/QueryPlan/FillingStep.cpp

@@ -11,15 +11,19 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
 }
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = false, /// TODO: it seem to actually be true. Check it later.
             .returns_single_stream = true,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = false,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/FilterStep.cpp

@@ -7,15 +7,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(const ExpressionActionsPtr & expression)
+static ITransformingStep::Traits getTraits(const ExpressionActionsPtr & expression)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = !expression->hasJoinOrArrayJoin(), /// I suppose it actually never happens
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = false,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/FinishSortingStep.cpp

@@ -9,15 +9,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(size_t limit)
+static ITransformingStep::Traits getTraits(size_t limit)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = limit == 0,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = limit == 0,
+        }
     };
 }
 

src/Processors/QueryPlan/ITransformingStep.cpp

@@ -4,19 +4,20 @@
 namespace DB
 {
 
-ITransformingStep::ITransformingStep(DataStream input_stream, Block output_header, DataStreamTraits traits, bool collect_processors_)
-    : collect_processors(collect_processors_)
-    , transform_traits(traits)
+ITransformingStep::ITransformingStep(DataStream input_stream, Block output_header, Traits traits, bool collect_processors_)
+    : transform_traits(std::move(traits.transform_traits))
+    , collect_processors(collect_processors_)
+    , data_stream_traits(std::move(traits.data_stream_traits))
 {
     output_stream = DataStream{.header = std::move(output_header)};
 
-    if (traits.preserves_distinct_columns)
+    if (data_stream_traits.preserves_distinct_columns)
         output_stream->distinct_columns = input_stream.distinct_columns;
 
-    output_stream->has_single_port = traits.returns_single_stream
-                                     || (input_stream.has_single_port && traits.preserves_number_of_streams);
+    output_stream->has_single_port = data_stream_traits.returns_single_stream
+                                     || (input_stream.has_single_port && data_stream_traits.preserves_number_of_streams);
 
-    if (traits.preserves_sorting)
+    if (data_stream_traits.preserves_sorting)
     {
         output_stream->sort_description = input_stream.sort_description;
         output_stream->sort_mode = input_stream.sort_mode;

src/Processors/QueryPlan/ITransformingStep.h

@@ -9,6 +9,8 @@ namespace DB
 class ITransformingStep : public IQueryPlanStep
 {
 public:
+    /// This flags are used to automatically set properties for output stream.
+    /// They are specified in constructor and cannot be changed.
     struct DataStreamTraits
     {
         /// Keep distinct_columns unchanged.
@@ -24,22 +26,34 @@ public:
         /// Examples: true for ExpressionStep, false for MergeSortingStep
         bool preserves_number_of_streams;
 
-        /// Won't change the total number of rows.
-        /// Examples: true ExpressionStep (without join or array join), false for FilterStep
-        bool preserves_number_of_rows;
-
         /// Doesn't change row order.
         /// Examples: true FilterStep, false for PartialSortingStep
         bool preserves_sorting;
     };
 
-    ITransformingStep(DataStream input_stream, Block output_header, DataStreamTraits traits, bool collect_processors_ = true);
+    /// This flags are used by QueryPlan optimizers.
+    /// They can be changed after some optimizations.
+    struct TransformTraits
+    {
+        /// Won't change the total number of rows.
+        /// Examples: true ExpressionStep (without join or array join), false for FilterStep
+        bool preserves_number_of_rows;
+    };
+
+    struct Traits
+    {
+        DataStreamTraits data_stream_traits;
+        TransformTraits transform_traits;
+    };
+
+    ITransformingStep(DataStream input_stream, Block output_header, Traits traits, bool collect_processors_ = true);
 
     QueryPipelinePtr updatePipeline(QueryPipelines pipelines) override;
 
     virtual void transformPipeline(QueryPipeline & pipeline) = 0;
 
-    const DataStreamTraits & getTransformTraits() const { return transform_traits; }
+    const TransformTraits & getTransformTraits() const { return transform_traits; }
+    const DataStreamTraits & getDataStreamTraits() const { return data_stream_traits; }
 
     void describePipeline(FormatSettings & settings) const override;
 
@@ -47,12 +61,14 @@ protected:
     /// Clear distinct_columns if res_header doesn't contain all of them.
     static void updateDistinctColumns(const Block & res_header, NameSet & distinct_columns);
 
+    TransformTraits transform_traits;
+
 private:
     /// We collect processors got after pipeline transformation.
     Processors processors;
     bool collect_processors;
 
-    DataStreamTraits transform_traits;
+    const DataStreamTraits data_stream_traits;
 };
 
 }

src/Processors/QueryPlan/LimitByStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = false,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/LimitStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = false,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/MergeSortingStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(size_t limit)
+static ITransformingStep::Traits getTraits(size_t limit)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = limit == 0,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = limit == 0,
+        }
     };
 }
 

src/Processors/QueryPlan/MergingAggregatedStep.cpp

@@ -7,15 +7,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = false,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = false,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/MergingSortedStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(size_t limit)
+static ITransformingStep::Traits getTraits(size_t limit)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = limit == 0,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = limit == 0,
+        }
     };
 }
 

src/Processors/QueryPlan/OffsetStep.cpp

@@ -6,15 +6,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = false,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/PartialSortingStep.cpp

@@ -7,15 +7,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(size_t limit)
+static ITransformingStep::Traits getTraits(size_t limit)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = false,
             .preserves_number_of_streams = true,
-            .preserves_number_of_rows = limit == 0,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = limit == 0,
+        }
     };
 }
 

src/Processors/QueryPlan/QueryPlan.cpp

@@ -315,7 +315,7 @@ static void tryPushDownLimit(QueryPlanStepPtr & parent, QueryPlanStepPtr & child
     if (!limit)
         return;
 
-    const auto * transforming = typeid_cast<const ITransformingStep *>(child.get());
+    const auto * transforming = dynamic_cast<const ITransformingStep *>(child.get());
 
     /// Skip everything which is not transform.
     if (!transforming)
@@ -323,14 +323,15 @@ static void tryPushDownLimit(QueryPlanStepPtr & parent, QueryPlanStepPtr & child
 
     /// Now we should decide if pushing down limit possible for this step.
 
-    const auto & traits = transforming->getTransformTraits();
+    const auto & transform_traits = transforming->getTransformTraits();
+    const auto & data_stream_traits = transforming->getDataStreamTraits();
 
     /// Cannot push down if child changes the number of rows.
-    if (!traits.preserves_number_of_rows)
+    if (!transform_traits.preserves_number_of_rows)
         return;
 
     /// Cannot push down if data was sorted exactly by child stream.
-    if (!child->getOutputStream().sort_description.empty() && !traits.preserves_sorting)
+    if (!child->getOutputStream().sort_description.empty() && !data_stream_traits.preserves_sorting)
         return;
 
     parent.swap(child);

src/Processors/QueryPlan/RollupStep.cpp

@@ -5,15 +5,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits()
+static ITransformingStep::Traits getTraits()
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = false,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = false,
             .preserves_sorting = false,
+        },
+        {
+            .preserves_number_of_rows = false,
+        }
     };
 }
 

src/Processors/QueryPlan/TotalsHavingStep.cpp

@@ -8,15 +8,19 @@
 namespace DB
 {
 
-static ITransformingStep::DataStreamTraits getTraits(bool has_filter)
+static ITransformingStep::Traits getTraits(bool has_filter)
 {
-    return ITransformingStep::DataStreamTraits
+    return ITransformingStep::Traits
     {
+        {
             .preserves_distinct_columns = true,
             .returns_single_stream = true,
             .preserves_number_of_streams = false,
-            .preserves_number_of_rows = !has_filter,
             .preserves_sorting = true,
+        },
+        {
+            .preserves_number_of_rows = !has_filter,
+        }
     };
 }