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 

{
    MergeTreeData * src_data = dynamic_cast<MergeTreeData *>(&source_table);
    if (!src_data)
        throw Exception("Table " + source_table.getStorageID().getNameForLogs() +
                        " supports attachPartitionFrom only for MergeTree family of table engines."
                        " Got " + source_table.getName(), ErrorCodes::NOT_IMPLEMENTED);
    if (my_snapshot->getColumns().getAllPhysical().sizeOfDifference(src_snapshot->getColumns().getAllPhysical()))
        throw Exception("Tables have different structure", ErrorCodes::INCOMPATIBLE_COLUMNS);
    auto query_to_string = [] (const ASTPtr & ast)
    {
        return ast ? queryToString(ast) : "";
    };
    if (query_to_string(my_snapshot->getSortingKeyAST()) != query_to_string(src_snapshot->getSortingKeyAST()))
        throw Exception("Tables have different ordering", ErrorCodes::BAD_ARGUMENTS);
    if (query_to_string(my_snapshot->getPartitionKeyAST()) != query_to_string(src_snapshot->getPartitionKeyAST()))
        throw Exception("Tables have different partition key", ErrorCodes::BAD_ARGUMENTS);
    if (format_version != src_data->format_version)
        throw Exception("Tables have different format_version", ErrorCodes::BAD_ARGUMENTS);
    return *src_data;
}
MergeTreeData & MergeTreeData::checkStructureAndGetMergeTreeData(