fix usage of 'distinct' combinator with 'state' combinator

src/AggregateFunctions/AggregateFunctionDistinct.h

@@ -236,6 +236,11 @@ public:
         return true;
     }
 
+    bool isState() const override
+    {
+        return nested_func->isState();
+    }
+
     AggregateFunctionPtr getNestedFunction() const override { return nested_func; }
 };
 

tests/queries/0_stateless/01259_combinator_distinct_distributed.reference

@@ -2,3 +2,7 @@
 [0,1,2,3,4,5,6,7,8,9,10,11,12]
 20
 0.49237
+78
+[0,1,2,3,4,5,6,7,8,9,10,11,12]
+20
+0.49237

tests/queries/0_stateless/01259_combinator_distinct_distributed.sql

+SET distributed_aggregation_memory_efficient = 1;
+
+SELECT sum(DISTINCT number % 13) FROM remote('127.0.0.{1,2}', numbers_mt(100000));
+SELECT arraySort(groupArray(DISTINCT number % 13)) FROM remote('127.0.0.{1,2}', numbers_mt(100000));
+SELECT finalizeAggregation(countState(DISTINCT toString(number % 20))) FROM remote('127.0.0.{1,2}', numbers_mt(100000));
+SELECT round(corrStable(DISTINCT x, y), 5) FROM (SELECT number % 10 AS x, number % 5 AS y FROM remote('127.0.0.{1,2}', numbers(1000)));
+
+SET distributed_aggregation_memory_efficient = 0;
+
 SELECT sum(DISTINCT number % 13) FROM remote('127.0.0.{1,2}', numbers_mt(100000));
 SELECT arraySort(groupArray(DISTINCT number % 13)) FROM remote('127.0.0.{1,2}', numbers_mt(100000));
 SELECT finalizeAggregation(countState(DISTINCT toString(number % 20))) FROM remote('127.0.0.{1,2}', numbers_mt(100000));