[phobos] For review: Improvements to std.variant and std.json

[Robert Jacques]

On Sun, 13 Feb 2011 13:50:19 -0500, Lutger Blijdestijn  
<lutger.blijdestijn at gmail.com> wrote:
> Hi, I just wanted to comment on the dson file format.
>
> While perhaps less efficient, the mongodb nosql database also uses a  
> binary
> json (bson) format to store data. It implements some extra types though.  
> I
> suggest that if you want to implement binary json, to seriously consider
> adopting bson instead:
>
> http://bsonspec.org/
>
> <http://bsonspec.org/>

Hi, I'm aware of the BSON format and have given it a decent review/reading  
(along with a few other serialization formats). As was noted in the JSON  
documentation BSON doesn't support all JSON types and has serious size and  
performance issues. First and foremost, BSON doesn't support true arrays;  
"arrays" are actually maps with integer keys. And it doesn't support  
80-bit reals, (which will probably be a deficiency of all non-D specific  
formats.) Add in all the legacy/proprietary stuff and the in-memory/C  
design optimization, and it's really not attractive as a stand alone  
serial format. Also, Mongodb has a 4mb Document limit, which IIRC is  
assumed by many of the BSON implementations to be the BSON size limit as  
well. My main purpose behind a binary json format was to store/read a data  
table, which was originally quite small and now is quite large, in a more  
efficient manner. Long term, I'm thinking of dropping this functionality  
in favor of a customized D binary serial format.