Merge pull request ClickHouse#87193 from ClickHouse/backport/25.8/87014

Backport ClickHouse#87014 to 25.8: Fix uniqExact incorrect result with ROLLUP/CUBE

Author: nickitat

src/AggregateFunctions/UniqExactSet.h

@@ -132,7 +132,7 @@ class UniqExactSet
         }
         else
         {
-            auto & lhs = asTwoLevel();
+            auto & lhs = asTwoLevelChecked();
 
             if (other.isSingleLevel())
                 return lhs.merge(other.asSingleLevel());
@@ -225,6 +225,7 @@ class UniqExactSet
     /// To convert set to two level before merging (we cannot just call convertToTwoLevel() on right hand side set, because it is declared const).
     std::shared_ptr<TwoLevelSet> getTwoLevelSet() const
     {
+        doDeepCopyIfNeeded();
         return two_level_set ? two_level_set : std::make_shared<TwoLevelSet>(asSingleLevel());
     }
 
@@ -243,10 +244,28 @@ class UniqExactSet
     SingleLevelSet & asSingleLevel() { return single_level_set; }
     const SingleLevelSet & asSingleLevel() const { return single_level_set; }
 
+    TwoLevelSet & asTwoLevelChecked()
+    {
+        doDeepCopyIfNeeded();
+        return *two_level_set;
+    }
+
     TwoLevelSet & asTwoLevel() { return *two_level_set; }
     const TwoLevelSet & asTwoLevel() const { return *two_level_set; }
 
+    /// Needed when a row can participate in more than one merge, e.g., ROLLUP/CUBE
+    void doDeepCopyIfNeeded() const
+    {
+        if (two_level_set && two_level_set.use_count() > 1)
+        {
+            auto copy = std::make_shared<TwoLevelSet>(two_level_set->size());
+            for (size_t i = 0; i < two_level_set->NUM_BUCKETS; ++i)
+                copy->impls[i].merge(two_level_set->impls[i]);
+            two_level_set = std::move(copy);
+        }
+    }
+
     SingleLevelSet single_level_set;
-    std::shared_ptr<TwoLevelSet> two_level_set;
+    mutable std::shared_ptr<TwoLevelSet> two_level_set;
 };
 }

tests/queries/0_stateless/03611_uniqExact_bug.reference

@@ -0,0 +1,17 @@
+--- ROLLUP ---
+1071106	999994
+1071102	999994
+0	1999988
+--- CUBE ---
+1071106	999994
+1071102	999994
+0	1999988
+--- totals ---
+1071106	999994
+1071102	999994
+
+0	1999988
+--- grouping sets ---
+1071106	999994
+1071102	999994
+0	1999988

tests/queries/0_stateless/03611_uniqExact_bug.sql

@@ -0,0 +1,59 @@
+set max_threads=4;
+
+create table test(c1 Int64, c2 Int64)
+Engine=MergeTree ORDER BY c2 AS  
+WITH gen as 
+  (SELECT xxHash32(number)   % 1000000 AS u1,
+          xxHash32(number+12345) % 1000000 AS u2
+   FROM numbers(1e6))
+SELECT
+    1071106,
+    5+(1 + 151703 * ((2 * u1) * (2 * u2)))
+FROM gen
+union all
+SELECT
+    1071102,
+    8+(1 + 151693 * ((2 * u1) * (2 * u2)))
+FROM gen;
+
+select '--- ROLLUP ---' format TSVRaw;
+SELECT
+    c1,
+    uniqExact(c2)
+FROM test
+GROUP BY c1
+    WITH ROLLUP
+ORDER BY c1 DESC;
+
+select '--- CUBE ---' format TSVRaw;
+
+SELECT
+    c1,
+    uniqExact(c2)
+FROM test
+GROUP BY c1
+    WITH CUBE
+ORDER BY c1 DESC;
+
+select '--- totals ---' format TSVRaw;
+
+SELECT
+    c1,
+    uniqExact(c2)
+FROM test
+GROUP BY c1
+    WITH TOTALS
+ORDER BY c1 DESC;
+
+select '--- grouping sets ---' format TSVRaw;
+
+SELECT
+    c1,
+    uniqExact(c2)
+FROM test
+GROUP BY 
+    GROUPING SETS(
+      (c1),
+      ()
+    )
+ORDER BY c1 DESC;