Deal with empty alias too

Author: Algunenano

src/Interpreters/OptimizeIfWithConstantConditionVisitor.cpp

@@ -109,7 +109,8 @@ void OptimizeIfWithConstantConditionVisitorData::visit(ASTFunction & function_no
 
         if (replace_alias.empty())
         {
-            replace_ast->setAlias(if_alias);
+            if (!if_alias.empty())
+                replace_ast->setAlias(if_alias);
             ast = replace_ast;
         }
         else
@@ -118,12 +119,14 @@ void OptimizeIfWithConstantConditionVisitorData::visit(ASTFunction & function_no
             /// But IAST has only method for deep copy of subtree.
             /// This can be a reason of performance degradation in case of deep queries.
             ASTPtr replace_ast_deep_copy = replace_ast->clone();
-            replace_ast_deep_copy->setAlias(if_alias);
+            if (!if_alias.empty())
+                replace_ast_deep_copy->setAlias(if_alias);
             ast = replace_ast_deep_copy;
         }
 
         if (!if_alias.empty())
         {
+            ast->setAlias(if_alias);
             auto alias_it = aliases.find(if_alias);
             if (alias_it != aliases.end() && alias_it->second.get() == child_copy.get())
                 alias_it->second = ast;