Merge pull request #59635 from ClickHouse/backport/23.11/59603

Backport #59603 to 23.11: Fix crash in topK when merging empty states
ClickHouse · Feb 6, 2024 · bd86804 · bd86804
2 parents 043a92f + 49a69d4
commit bd86804
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diff --git a/src/AggregateFunctions/AggregateFunctionTopK.cpp b/src/AggregateFunctions/AggregateFunctionTopK.cpp
@@ -235,6 +235,9 @@ class AggregateFunctionTopKGeneric
 
     void merge(AggregateDataPtr __restrict place, ConstAggregateDataPtr rhs, Arena *) const override
     {
+        if (!this->data(rhs).value.size())
+            return;
+
         auto & set = this->data(place).value;
         if (set.capacity() != reserved)
             set.resize(reserved);

diff --git a/src/Common/SpaceSaving.h b/src/Common/SpaceSaving.h
@@ -206,6 +206,9 @@ class SpaceSaving
      */
     void merge(const Self & rhs)
     {
+        if (!rhs.size())
+            return;
+
         UInt64 m1 = 0;
         UInt64 m2 = 0;
 

diff --git a/tests/queries/0_stateless/02984_topk_empty_merge.reference b/tests/queries/0_stateless/02984_topk_empty_merge.reference
@@ -0,0 +1 @@
+[]
diff --git a/tests/queries/0_stateless/02984_topk_empty_merge.sql b/tests/queries/0_stateless/02984_topk_empty_merge.sql
@@ -0,0 +1,2 @@
+-- https://github.com/ClickHouse/ClickHouse/issues/59107
+SELECT topK('102.4') FROM remote('127.0.0.{1,2}', view(SELECT NULL FROM system.one WHERE dummy = 1));