Change the table comment after created the table is not supported now?
Like mysql : ALTER TABLE [tableName] COMMNET [comment]; 
The sql "ALTER TABLE `system`.tables UPDATE Comment='test' WHERE NAME='t1';" also not supported!!!
My version is '21.9.4.35'。
stage_in_source_tables = std::max(
                    stage_in_source_tables,
                    table->getQueryProcessingStage(local_context, to_stage, table->getInMemoryMetadataPtr(), query_info));
            }
            iterator->next();
        }
    }
    return selected_table_size == 1 ? stage_in_source_tables : std::min(stage_in_source_tables, QueryProcessingStage::WithMergeableState);
}
Pipe StorageMerge::read(
    const Names & column_names,
    const StorageMetadataPtr & metadata_snapshot,
    SelectQueryInfo & query_info,
    ContextPtr local_context,
    QueryProcessingStage::Enum processed_stage,
    const size_t max_block_size,
    unsigned num_streams)
{
    Pipes pipes;
    bool has_database_virtual_column = false;
    bool has_table_virtual_column = false;
    Names real_column_names;
    real_column_names.reserve(column_names.size());
    for (const auto & column_name : column_names)
    {
        if (column_name == "_database" && isVirtualColumn(column_name, metadata_snapshot))
            has_database_virtual_column = true;
        else if (column_name == "_table" && isVirtualColumn(column_name, metadata_snapshot))
            has_table_virtual_column = true;
        else