fixes

src/Interpreters/InterpreterSelectQuery.cpp

@@ -1847,26 +1847,36 @@ static bool windowDescriptionComparator(const WindowDescription * _left,
         {
             return true;
         }
-
-        if (left[i].column_number < right[i].column_number)
-        {
-            return true;
-        }
-
-        if (left[i].direction < right[i].direction)
-        {
-            return true;
-        }
-
-        if (left[i].nulls_direction < right[i].nulls_direction)
-        {
-            return true;
-        }
-
-        if (left[i] != right[i])
+        else if (left[i].column_name > right[i].column_name)
         {
             return false;
         }
+        else if (left[i].column_number < right[i].column_number)
+        {
+            return true;
+        }
+        else if (left[i].column_number > right[i].column_number)
+        {
+            return false;
+        }
+        else if (left[i].direction < right[i].direction)
+        {
+            return true;
+        }
+        else if (left[i].direction > right[i].direction)
+        {
+            return false;
+        }
+        else if (left[i].nulls_direction < right[i].nulls_direction)
+        {
+            return true;
+        }
+        else if (left[i].nulls_direction > right[i].nulls_direction)
+        {
+            return false;
+        }
+
+        assert(left[i] == right[i]);
     }
 
     // Note that we check the length last, because we want to put together the

src/Processors/Transforms/WindowTransform.cpp

@@ -798,10 +798,10 @@ void WindowTransform::updateAggregationState()
             // For now, add the values one by one.
             auto * columns = ws.argument_columns.data();
             // Removing arena.get() from the loop makes it faster somehow...
-            auto * _arena = arena.get();
+            auto * arena_ = arena.get();
             for (auto row = first_row; row < past_the_end_row; ++row)
             {
-                a->add(buf, columns, row, _arena);
+                a->add(buf, columns, row, arena_);
             }
         }
     }

tests/queries/0_stateless/01591_window_functions.reference

@@ -912,3 +912,11 @@ Expression ((Projection + Before ORDER BY))
                   Expression ((Before window functions + (Projection + Before ORDER BY)))
                     SettingQuotaAndLimits (Set limits and quota after reading from storage)
                       ReadFromStorage (SystemNumbers)
+-- A test case for the sort comparator found by fuzzer.
+SELECT
+    max(number) OVER (ORDER BY number DESC NULLS FIRST),
+    max(number) OVER (ORDER BY number ASC NULLS FIRST)
+FROM numbers(2)
+;
+1	0
+1	1

tests/queries/0_stateless/01591_window_functions.sql

@@ -308,3 +308,10 @@ from
     (select number, intDiv(number, 3) p, mod(number, 5) o
         from numbers(16)) t
 ;
+
+-- A test case for the sort comparator found by fuzzer.
+SELECT
+    max(number) OVER (ORDER BY number DESC NULLS FIRST),
+    max(number) OVER (ORDER BY number ASC NULLS FIRST)
+FROM numbers(2)
+;