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'。
if (auto * select_query = select.list_of_selects->children.at(0)->as<ASTSelectQuery>())
        {
            JoinedTables joined_tables(Context::createCopy(local_context), *select_query);
            if (joined_tables.tablesCount() == 1)
            {
                storage_src = std::dynamic_pointer_cast<StorageDistributed>(joined_tables.getLeftTableStorage());
                if (storage_src)
                {
                    const auto select_with_union_query = std::make_shared<ASTSelectWithUnionQuery>();
                    select_with_union_query->list_of_selects = std::make_shared<ASTExpressionList>();
                    auto new_select_query = std::dynamic_pointer_cast<ASTSelectQuery>(select_query->clone());
                    select_with_union_query->list_of_selects->children.push_back(new_select_query);
                    new_select_query->replaceDatabaseAndTable(storage_src->getRemoteDatabaseName(), storage_src->getRemoteTableName());
                    new_query->select = select_with_union_query;
                }
            }
        }
    }
    if (!storage_src || storage_src->getClusterName() != getClusterName())
    {
        return nullptr;
    }
    if (settings.parallel_distributed_insert_select == PARALLEL_DISTRIBUTED_INSERT_SELECT_ALL)
    {
        new_query->table_id = StorageID(getRemoteDatabaseName(), getRemoteTableName());
    }
    const auto & cluster = getCluster();
    const auto & shards_info = cluster->getShardsInfo();
    std::vector<std::unique_ptr<QueryPipelineBuilder>> pipelines;
    String new_query_str = queryToString(new_query);