better

src/Columns/ColumnNullable.cpp

@@ -334,8 +334,6 @@ void ColumnNullable::updatePermutation(bool reverse, size_t limit, int null_dire
     if (equal_ranges.empty())
         return;
 
-    std::cout << "limit " << limit << std::endl;
-
     /// We will sort nested columns into `new_ranges` and call updatePermutation in next columns with `null_ranges`.
     EqualRanges new_ranges, null_ranges;
 
@@ -347,7 +345,7 @@ void ColumnNullable::updatePermutation(bool reverse, size_t limit, int null_dire
         for (const auto & [first, last] : equal_ranges)
         {
             /// Current interval is righter than limit. 
-            if (first > limit) 
+            if (limit && first > limit)
                 break;
 
             /// Consider a half interval [first, last)
@@ -404,7 +402,7 @@ void ColumnNullable::updatePermutation(bool reverse, size_t limit, int null_dire
         for (const auto & [first, last] : equal_ranges)
         {
             /// Current interval is righter than limit.
-            if (first > limit)
+            if (limit && first > limit)
                 break;
 
             ssize_t read_idx = last - 1;
@@ -439,15 +437,7 @@ void ColumnNullable::updatePermutation(bool reverse, size_t limit, int null_dire
         }
     }
 
-    std::cout << "New Ranges " << std::endl;
-    for (auto [first, last] : new_ranges )
-        std::cout << "first " << first << " last " << last << std::endl;
-
-    std::cout << "Null Ranges " << std::endl;
-    for (auto [first, last] : null_ranges) 
-        std::cout << "first " << first << " last " << last << std::endl;
-
-    getNestedColumn().updatePermutation(reverse, 0, null_direction_hint, res, new_ranges);
+    getNestedColumn().updatePermutation(reverse, limit, null_direction_hint, res, new_ranges);
 
     equal_ranges = std::move(new_ranges);
     std::move(null_ranges.begin(), null_ranges.end(), std::back_inserter(equal_ranges));

src/Columns/ColumnVector.cpp

@@ -18,6 +18,8 @@
 #include <pdqsort.h>
 #include <numeric>
 
+#include <ext/scope_guard.h>
+
 #if !defined(ARCADIA_BUILD)
 #    include <Common/config.h>
 #    if USE_OPENCL
@@ -250,6 +252,7 @@ void ColumnVector<T>::updatePermutation(bool reverse, size_t limit, int nan_dire
         limit = 0;
 
     EqualRanges new_ranges;
+    SCOPE_EXIT({equal_range = std::move(new_ranges);});
 
     for (size_t i = 0; i < equal_range.size() - bool(limit); ++i)
     {
@@ -278,6 +281,12 @@ void ColumnVector<T>::updatePermutation(bool reverse, size_t limit, int nan_dire
     if (limit)
     {
         const auto & [first, last] = equal_range.back();
+
+        if (limit < first || limit >= last)
+            return;
+
+        /// Since then, we are working inside the interval.
+
         if (reverse)
             std::partial_sort(res.begin() + first, res.begin() + limit, res.begin() + last, greater(*this, nan_direction_hint));
         else
@@ -310,7 +319,6 @@ void ColumnVector<T>::updatePermutation(bool reverse, size_t limit, int nan_dire
             new_ranges.emplace_back(new_first, new_last);
         }
     }
-    equal_range = std::move(new_ranges);
 }
 
 template <typename T>