Re: [PATCH 4/8] netbox: extend codec with 'decode' methods

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Mon, Apr 16, 2018 at 09:39:14PM +0300, Vladislav Shpilevoy wrote:
> Netbox has a table 'method_codec' that is used to encode a
> request by a method name. But a response is decoded out of codec.
> It leads to
> 1) decoding into Lua tables before decoding into tuples where
> needed - it is double decoding and produces a lot of garbage;
> 2) each method contains hacks like one_tuple(), or single tuple
> check.
> 
> These things can not be fixed with no real codec instead of
> encoder only.
> 
> Also global table with decoders is needed for #3107, where
> a request could be sent async with no fiber blocking. An async
> response when received already does not have a call context - it
> has only method name.
> 
> Needed for #3107
> ---
>  src/box/lua/net_box.lua | 116 +++++++++++++++++++++++++++++-------------------
>  test/box/net.box.result |  14 ++++++
>  test/box/sql.result     |   2 +
>  3 files changed, 87 insertions(+), 45 deletions(-)
> 
> diff --git a/src/box/lua/net_box.lua b/src/box/lua/net_box.lua
> index 4ed2b375d..3868cdf1c 100644
> --- a/src/box/lua/net_box.lua
> +++ b/src/box/lua/net_box.lua
> @@ -50,7 +50,34 @@ local E_PROC_LUA             = box.error.PROC_LUA
>  
>  -- utility tables
>  local is_final_state         = {closed = 1, error = 1}
> -local method_codec           = {
> +
> +local function decode_nil(...) end

> +local function decode_nothing(...) return ... end

decode_nop, may be?

> +local function decode_one_tuple(response)
> +    if response[1] then
> +        return box.tuple.new(response[1])
> +    end
> +end
> +local function decode_single_tuple(response)
> +    if response[2] then
> +        return nil, box.error.MORE_THAN_ONE_TUPLE
> +    end
> +    if response[1] then
> +        return box.tuple.new(response[1])
> +    end
> +end

Do we really need this MORE_THAN_ONE_TUPLE error? Can't we use
decode_one_tuple in 'get' as well? I ask, because having two methods
called decode_one_tuple and decode_single_tuple is confusing IMO -
it's unclear what's the difference between them.

> +local function decode_select(response)
> +    setmetatable(response, sequence_mt)
> +    for i, v in pairs(response) do
> +        response[i] = box.tuple.new(v)
> +    end
> +    return response
> +end
> +local function decode_count(response)
> +    return response[1]
> +end
> +
> +local method_encoder = {
>      ping    = internal.encode_ping,
>      call_16 = internal.encode_call_16,
>      call_17 = internal.encode_call,
> @@ -61,6 +88,10 @@ local method_codec           = {
>      update  = internal.encode_update,
>      upsert  = internal.encode_upsert,
>      select  = internal.encode_select,
> +    get     = internal.encode_select,
> +    min     = internal.encode_select,
> +    max     = internal.encode_select,
> +    count   = internal.encode_call,
>      -- inject raw data into connection, used by console and tests
>      inject = function(buf, id, schema_version, bytes)
>          local ptr = buf:reserve(#bytes)
> @@ -69,6 +100,24 @@ local method_codec           = {
>      end
>  }
>  
> +local method_decoder = {
> +    ping    = decode_nil,
> +    call_16 = decode_select,
> +    call_17 = decode_nothing,
> +    eval    = decode_nothing,
> +    insert  = decode_one_tuple,
> +    replace = decode_one_tuple,
> +    delete  = decode_one_tuple,
> +    update  = decode_one_tuple,
> +    upsert  = decode_nil,
> +    select  = decode_select,
> +    get     = decode_single_tuple,
> +    min     = decode_single_tuple,
> +    max     = decode_single_tuple,
> +    count   = decode_count,
> +    inject  = decode_nothing,
> +}
> +
>  local function next_id(id) return band(id + 1, 0x7FFFFFFF) end
>  
>  --

> @@ -1144,9 +1175,8 @@ index_metatable = function(remote)
>          if opts and opts.buffer then
>              error("index:min() doesn't support `buffer` argument")
>          end
> -        local res = remote:_request('select', opts, self.space.id, self.id,
> -                                    box.index.GE, 0, 1, key)
> -        return one_tuple(res)
> +        return remote:_request('get', opts, self.space.id, self.id,

Should be 'min'?

> +                               box.index.GE, 0, 1, key)
>      end
>  
>      function methods:max(key, opts)
> @@ -1154,9 +1184,8 @@ index_metatable = function(remote)
>          if opts and opts.buffer then
>              error("index:max() doesn't support `buffer` argument")
>          end
> -        local res = remote:_request('select', opts, self.space.id, self.id,
> -                                    box.index.LE, 0, 1, key)
> -        return one_tuple(res)
> +        return remote:_request('get', opts, self.space.id, self.id,

Should be 'max'?

> +                               box.index.LE, 0, 1, key)
>      end
>  
>      function methods:count(key, opts)