implement split range on MergeTreeReadPoolParallelReplicasInOrder

src/Storages/MergeTree/MergeTreeReadPoolParallelReplicasInOrder.cpp

@@ -1,4 +1,5 @@
 #include <Storages/MergeTree/MergeTreeReadPoolParallelReplicasInOrder.h>
+#include <Storages/MergeTree/MergeTreeSettings.h>
 
 namespace ProfileEvents
 {
@@ -14,6 +15,11 @@ namespace ErrorCodes
     extern const int BAD_ARGUMENTS;
 }
 
+namespace MergeTreeSetting
+{
+    extern const MergeTreeSettingsUInt64 index_granularity;
+}
+
 MergeTreeReadPoolParallelReplicasInOrder::MergeTreeReadPoolParallelReplicasInOrder(
     ParallelReadingExtension extension_,
     CoordinationMode mode_,
@@ -70,16 +76,73 @@ MergeTreeReadTaskPtr MergeTreeReadPoolParallelReplicasInOrder::getTask(size_t ta
             task_idx, per_part_infos.size());
 
     const auto & part_info = per_part_infos[task_idx]->data_part->info;
-    auto get_from_buffer = [&]() -> std::optional<MarkRanges>
+    const auto & data_settings = per_part_infos[task_idx]->data_part->storage.getSettings();
+    auto get_from_buffer = [&, 
+    rows_granularity = (*data_settings)[MergeTreeSetting::index_granularity], 
+    my_max_block_size = this->block_size_params.max_block_size_rows]() -> std::optional<MarkRanges>
     {
+        const size_t max_marks_in_range = (my_max_block_size + rows_granularity - 1) / rows_granularity;
         for (auto & desc : buffered_tasks)
         {
             if (desc.info == part_info && !desc.ranges.empty())
             {
-                auto result = std::move(desc.ranges);
+                if (mode == CoordinationMode::WithOrder)
-                desc.ranges = MarkRanges{};
+                {
-                ProfileEvents::increment(ProfileEvents::ParallelReplicasReadMarks, desc.ranges.getNumberOfMarks());
+                    /// if already splited, just return desc.ranges
-                return result;
+                    if (split)
+                    {
+                        auto result = std::move(desc.ranges);
+                        desc.ranges = MarkRanges{};
+                        ProfileEvents::increment(ProfileEvents::ParallelReplicasReadMarks, result.getNumberOfMarks());
+                        return result;
+                    }
+
+                    /// else split range but still return all MarkRanges
+                    MarkRanges result;
+                    for (auto range : desc.ranges)
+                    {
+                        while (!split && range.begin + marks_in_range < range.end)
+                        {
+                            result.emplace_back(range.begin, range.begin + marks_in_range);
+                            range.begin += marks_in_range;
+                            marks_in_range *= 2;
+                            if (marks_in_range > max_marks_in_range)
+                                split = true;
+                        }
+                        result.emplace_back(range.begin, range.begin + marks_in_range);
+                    }
+                    chassert(!result.empty());
+                    desc.ranges = MarkRanges{};
+                    ProfileEvents::increment(ProfileEvents::ParallelReplicasReadMarks, result.getNumberOfMarks());
+                    return result;
+                }
+                else
+                {
+                    /// for reverse order just reutrn one range
+                    MarkRanges result;
+                    auto & range = desc.ranges.back();
+                    if (range.begin + marks_in_range < range.end)
+                    {
+                        result.emplace_front(range.end - marks_in_range, range.end);
+                        range.end -= marks_in_range;
+                        marks_in_range = std::min(marks_in_range * 2, max_marks_in_range);
+                    }
+                    else 
+                    {
+                        result.emplace_front(range.begin, range.end);
+                        desc.ranges.pop_back();
+                    }
+                    
+                    /// TODO: should we need reset for each ranges?
+                    if (desc.ranges.empty())
+                    {
+                        marks_in_range = 1;
+                    }
+
+                    chassert(result.size() == 1);
+                    ProfileEvents::increment(ProfileEvents::ParallelReplicasReadMarks, result.getNumberOfMarks());
+                    return result;
+                }
             }
         }
         return std::nullopt;

src/Storages/MergeTree/MergeTreeReadPoolParallelReplicasInOrder.h

@@ -38,6 +38,8 @@ private:
     RangesInDataPartsDescription buffered_tasks;
 
     mutable std::mutex mutex;
+    bool split{false};
+    size_t marks_in_range{1};
 };
 
 };