Fix: DISTINCT in order with zero values in non-sorted columns

src/Common/HashTable/ClearableHashSet.h

@@ -88,6 +88,9 @@ public:
     {
         ++this->version;
         this->m_size = 0;
+
+        /// clear ZeroValueStorage
+        this->clearHasZero();
     }
 };
 
@@ -108,6 +111,9 @@ public:
     {
         ++this->version;
         this->m_size = 0;
+
+        /// clear ZeroValueStorage
+        this->clearHasZero();
     }
 };
 

tests/queries/0_stateless/02733_fix_distinct_in_order_bug_49622.reference

@@ -0,0 +1,2 @@
+	1
+	2

tests/queries/0_stateless/02733_fix_distinct_in_order_bug_49622.sql

@@ -0,0 +1,15 @@
+set optimize_distinct_in_order=1;
+
+DROP TABLE IF EXISTS test;
+
+CREATE TABLE test
+(
+    `c1` String,
+    `c2` String
+)
+ENGINE = MergeTree
+ORDER BY c1;
+
+INSERT INTO test(c1, c2) VALUES ('1',  ''), ('2', '');
+
+SELECT DISTINCT c2, c1 FROM test FORMAT TSV;