Lowered CPU overhead for small data parts

dbms/src/Storages/MergeTree/MergeTreeReadPool.cpp

@@ -129,12 +129,12 @@ MergeTreeReadTaskPtr MergeTreeReadPool::getTask(const size_t min_marks_to_read,
         prewhere_info && prewhere_info->remove_prewhere_column, per_part_should_reorder[part_idx], std::move(curr_task_size_predictor));
 }
 
-MarkRanges MergeTreeReadPool::getRestMarks(const std::string & part_path, const MarkRange & from) const
+MarkRanges MergeTreeReadPool::getRestMarks(const MergeTreeDataPart & part, const MarkRange & from) const
 {
     MarkRanges all_part_ranges;
     for (const auto & part_ranges : parts_ranges)
     {
-        if (part_ranges.data_part->getFullPath() == part_path)
+        if (part_ranges.data_part.get() == &part)
         {
             all_part_ranges = part_ranges.ranges;
             break;
@@ -142,7 +142,7 @@ MarkRanges MergeTreeReadPool::getRestMarks(const std::string & part_path, const
     }
     if (all_part_ranges.empty())
         throw Exception("Trying to read marks range [" + std::to_string(from.begin) + ", " + std::to_string(from.end) + "] from part '"
-                        + part_path + "' which has no ranges in this query", ErrorCodes::LOGICAL_ERROR);
+            + part.getFullPath() + "' which has no ranges in this query", ErrorCodes::LOGICAL_ERROR);
 
     auto begin = std::lower_bound(all_part_ranges.begin(), all_part_ranges.end(), from, [] (const auto & f, const auto & s) { return f.begin < s.begin; });
     if (begin == all_part_ranges.end())

dbms/src/Storages/MergeTree/MergeTreeReadPool.h

@@ -81,7 +81,7 @@ public:
     void profileFeedback(const ReadBufferFromFileBase::ProfileInfo info);
 
     /// This method tells which mark ranges we have to read if we start from @from mark range
-    MarkRanges getRestMarks(const std::string & part_path, const MarkRange & from) const;
+    MarkRanges getRestMarks(const MergeTreeDataPart & part, const MarkRange & from) const;
 
     Block getHeader() const;
 

dbms/src/Storages/MergeTree/MergeTreeThreadSelectBlockInputStream.cpp

@@ -74,7 +74,7 @@ bool MergeTreeThreadSelectBlockInputStream::getNewTask()
 
     if (!reader)
     {
-        auto rest_mark_ranges = pool->getRestMarks(path, task->mark_ranges[0]);
+        auto rest_mark_ranges = pool->getRestMarks(*task->data_part, task->mark_ranges[0]);
 
         if (use_uncompressed_cache)
             owned_uncompressed_cache = storage.global_context.getUncompressedCache();
@@ -95,7 +95,7 @@ bool MergeTreeThreadSelectBlockInputStream::getNewTask()
         /// in other case we can reuse readers, anyway they will be "seeked" to required mark
         if (path != last_readed_part_path)
         {
-            auto rest_mark_ranges = pool->getRestMarks(path, task->mark_ranges[0]);
+            auto rest_mark_ranges = pool->getRestMarks(*task->data_part, task->mark_ranges[0]);
             /// retain avg_value_size_hints
             reader = std::make_unique<MergeTreeReader>(
                 path, task->data_part, task->columns, owned_uncompressed_cache.get(), owned_mark_cache.get(), save_marks_in_cache,