[Tarantool-patches] [PATCH resend v2 08/11] lua, datetime: calculated attributes for datetimes

[Timur Safin]

Hello Oleg again!

: From: Oleg Babin <olegrok at tarantool.org>
: Subject: Re: [Tarantool-patches] [PATCH resend v2 08/11] lua, datetime:
: calculated attributes for datetimes
: 
: Thanks for your patch. See one comment below.
: 
: Also this change should be squashed into the first patch.

Agreed as well. 

: 
: 
: On 28.07.2021 13:34, Timur Safin via Tarantool-patches wrote:
: > * introduced a set of calculated attributes to data object, e.g.:
: >    - timestamp, seconds, microseconds, minute, or hours
: >
: > Part of #5941
: > ---
: >   src/lua/datetime.lua           | 51 ++++++++++++++++++++++------------
: >   test/app-tap/datetime.test.lua | 17 +++++++++++-
: >   2 files changed, 50 insertions(+), 18 deletions(-)
: >
: > diff --git a/src/lua/datetime.lua b/src/lua/datetime.lua
: > index 9ec06d8d8..7a208cef9 100644
: > --- a/src/lua/datetime.lua
: > +++ b/src/lua/datetime.lua
: > @@ -224,6 +224,36 @@ local function interval_serialize(self)
: >       return { secs = self.secs, nsec = self.nsec }
: >   end
: >
: > +local datetime_index = function(self, key)
: > +    local attributes = {
: 
: This change looks like pessimization because currently we need to
: recreate "attributes" table
: 
: for each function call. I suggest to use `attributes` as `__index` but
: not such function.

What would you say if I simply precache this attributes table in local,
and then proceed this way?
-----------------------------------------
-local datetime_index = function(self, key)
-    local attributes = {
+local datetime_index_handlers = {
         unixtime = function(self)
             return self.secs
         end,
+
         timestamp = function(self)
             return tonumber(self.secs) + self.nsec / 1e9
         end,
+
         nanoseconds = function(self)
             return self.secs * 1e9 + self.nsec
         end,
+
         microseconds = function(self)
             return self.secs * 1e6 + self.nsec / 1e3
         end,
+
         milliseconds = function(self)
             return self.secs * 1e3 + self.nsec / 1e6
         end,
+
         seconds = function(self)
             return tonumber(self.secs) + self.nsec / 1e9
         end,
+
         minutes = function(self)
             return (tonumber(self.secs) + self.nsec / 1e9) / 60
         end,
+
         hours = function(self)
             return (tonumber(self.secs) + self.nsec / 1e9) / (60 * 60)
         end,
+
         days = function(self)
             return (tonumber(self.secs) + self.nsec / 1e9) / (60 * 60) / 24
         end,
+
         add = function(self)
             return function(self, o)
                 return interval_increment(self, o, 1)
             end
         end,
+
         sub = function(self)
             return function(self, o)
                 return interval_increment(self, o, -1)
             end
         end,
     }
-    return attributes[key] ~= nil and attributes[key](self) or nil
+
+local datetime_index = function(self, key)
+    return datetime_index_handlers[key] ~= nil and
+           datetime_index_handlers[key](self) or nil
 end
-----------------------------------------

I mean we still carefully check existence of an asked key, and return nil if
there is no such key at all. Is it much different than what you've meant?


: 
: 
: > +        timestamp = function(self)
: > +            return tonumber(self.secs) + self.nsec / 1e9
: > +        end,
: > +        nanoseconds = function(self)
: > +            return tonumber(self.secs * 1e9 + self.nsec)
: > +        end,
: > +        microseconds = function(self)
: > +            return tonumber(self.secs * 1e6 + self.nsec / 1e3)
: > +        end,
: > +        milliseconds = function(self)
: > +            return tonumber(self.secs * 1e3 + self.nsec / 1e6)
: > +        end,
: > +        seconds = function(self)
: > +            return tonumber(self.secs) + self.nsec / 1e9
: > +        end,
: > +        minutes = function(self)
: > +            return (tonumber(self.secs) + self.nsec / 1e9) / 60
: > +        end,
: > +        hours = function(self)
: > +            return (tonumber(self.secs) + self.nsec / 1e9) / (60 * 60)
: > +        end,
: > +        days = function(self)
: > +            return (tonumber(self.secs) + self.nsec / 1e9) / (60 * 60) /
: 24
: > +        end,
: > +    }
: > +    return attributes[key] ~= nil and attributes[key](self) or nil
: > +end
: > +
: >   local datetime_mt = {
: >       -- __tostring = datetime_tostring,
: >       __serialize = datetime_serialize,

Thanks,
Timur