I am reading clickhouse mutation code. In StorageMergeTree->selectPartsToMutate() function, there is a check 
`if (current_ast_elements + commands_size >= max_ast_elements)
                break;`

I think if there are many mutations then the check result will be true, so that it will skip the remaining mutations.
But the new part's mutation is set to the last one in mutation map, and it does not apply the remaining mutations actually.
`new_part_info.mutation = current_mutations_by_version.rbegin()->first;`

Then the new part will miss the remaining mutations in future mutation job.

I think it's wrong here. Am I right?

If it is right, I will submit a PR 

if (old_metadata.hasSortingKey())
    {
        
        
        Names new_primary_key_columns = new_primary_key.column_names;
        Names new_sorting_key_columns = new_sorting_key.column_names;
        ASTPtr added_key_column_expr_list = std::make_shared<ASTExpressionList>();
        const auto & old_sorting_key_columns = old_metadata.getSortingKeyColumns();
        for (size_t new_i = 0, old_i = 0; new_i < sorting_key_size; ++new_i)
        {
            if (old_i < old_sorting_key_columns.size())
            {
                if (new_sorting_key_columns[new_i] != old_sorting_key_columns[old_i])
                    added_key_column_expr_list->children.push_back(new_sorting_key.expression_list_ast->children[new_i]);
                else
                    ++old_i;
            }
            else
                added_key_column_expr_list->children.push_back(new_sorting_key.expression_list_ast->children[new_i]);
        }
        if (!added_key_column_expr_list->children.empty())
        {
            auto syntax = TreeRewriter(getContext()).analyze(added_key_column_expr_list, all_columns);
            Names used_columns = syntax->requiredSourceColumns();
            NamesAndTypesList deleted_columns;
            NamesAndTypesList added_columns;
            old_metadata.getColumns().getAllPhysical().getDifference(all_columns, deleted_columns, added_columns);
            for (const String & col : used_columns)
            {