[Tarantool-patches] [PATCH v2 2/3] box: introduce box_return_mp() public C function
Nikita Pettik
korablev at tarantool.org
Tue Apr 28 01:55:27 MSK 2020
On 27 Apr 23:29, Vladislav Shpilevoy wrote:
> Thanks for the question!
>
> On 27/04/2020 17:14, Nikita Pettik wrote:
> > On 23 Apr 02:12, Vladislav Shpilevoy wrote:
> >> +
> >> +int
> >> +test_return_mp(box_function_ctx_t *ctx, const char *args, const char *args_end)
> >> +{
> >> + (void) args;
> >> + (void) args_end;
> >> + char buf[512];
> >> + char *pos = mp_encode_uint(buf, 1);
> >> + int rc = box_return_mp(ctx, buf, pos);
> >> + if (rc != 0)
> >> + return rc;
> >> +
> >> + pos = mp_encode_int(buf, -1);
> >> + rc = box_return_mp(ctx, buf, pos);
> >> + if (rc != 0)
> >> + return rc;
> >> +
> >> + pos = mp_encode_uint(buf, UINT64_MAX);
> >> + rc = box_return_mp(ctx, buf, pos);
> >> + if (rc != 0)
> >> + return rc;
> >> +
> >> + const char *str = "123456789101112131415";
> >> + pos = mp_encode_str(buf, str, strlen(str));
> >> + rc = box_return_mp(ctx, buf, pos);
> >> + if (rc != 0)
> >> + return rc;
> >> +
> >> + pos = mp_encode_array(buf, 1);
> >> + pos = mp_encode_uint(pos, 2);
> >> + box_tuple_t *tuple = box_tuple_new(box_tuple_format_default(),
> >> + buf, pos);
> >> + if (tuple == NULL)
> >> + return -1;
> >> + rc = box_return_tuple(ctx, tuple);
> >
> > Probably I'm missing something (since I've never used C API) but
> > when I do:
> >
> > res = net:connect(box.cfg.listen):call(name)
> > print(type(res[5]))
> >
> > I get table. But shouldn't it be tuple (cdata), since it (last member)
> > is explicitly wrapped into tuple)? I guess it is due to certain
> > convention but failed to find it in docs. Could you please clarify?
>
> That is not about C functions. It is about tuple data type lost during
> its marshaling over network. You will get the same result, if you
> write that in a Lua stored function. We solve that problem by introducing
> MP_EXT to be able to restore types on the client side for uuids, errors,
> decimals. But not for tuples. So they turn into tables when
> serialized-deserialized from MessagePack during sending over the network.
Ok, thanks. Just in case - patch LGTM.
> Exception is IPROTO_SELECT and other DML/DQL mapped onto exact IPROTO_*
> commands, because client always knows they return tuples, and can create
> them on the client side instead of tables.
More information about the Tarantool-patches
mailing list