Merge pull request #51046 from ClickHouse/backport/23.3/50334

Backport #50334 to 23.3: Fix crash when Pool::Entry::disconnect() is called

src/Common/mysqlxx/Pool.cpp

@@ -40,14 +40,10 @@ void Pool::Entry::decrementRefCount()
     {
         /// We were the last user of this thread, deinitialize it
         mysql_thread_end();
-    }
-    else if (data->removed_from_pool)
-    {
-        /// data->ref_count == 0 in case we removed connection from pool (see Pool::removeConnection).
-        chassert(ref_count == 0);
         /// In Pool::Entry::disconnect() we remove connection from the list of pool's connections.
         /// So now we must deallocate the memory.
-        ::delete data;
+        if (data->removed_from_pool)
+            ::delete data;
     }
 }
 
@@ -234,11 +230,8 @@ void Pool::removeConnection(Connection* connection)
     std::lock_guard lock(mutex);
     if (connection)
     {
-        if (connection->ref_count > 0)
-        {
+        if (!connection->removed_from_pool)
             connection->conn.disconnect();
-            connection->ref_count = 0;
-        }
         connections.remove(connection);
         connection->removed_from_pool = true;
     }