Re: Endorsement, review manager sought for Boost.Mysql

From: Ruben Perez (rubenperez038_at_[hidden])
Date: 2021-03-10 14:13:22

On Wed, 10 Mar 2021 at 03:32, Edward Diener via Boost <boost_at_[hidden]>
wrote:

> On 3/9/2021 5:04 PM, Ruben Perez via Boost wrote:
> > Hi all,
> >
> > I would like to propose a MySQL client library for Boost (under the
> > original name of Boost.Mysql). It is a full implementation of the MySQL
> > client protocol, based on Boost.Asio. It requires C++11.
> >
> > The library is at https://github.com/anarthal/mysql and the
> documentation
> > is at https://anarthal.github.io/mysql/. Examples under
> > https://anarthal.github.io/mysql/mysql/examples.html.
> >
> > The purpose of this library is to provide a low-level building block for
> > applications or other libraries to interact with MySQL, in the same way
> > Boost.Beast provides a way to interact with HTTP. It complies with
> > Boost.Asio universal asynchronous model, and provides the usual sync and
> > async overloads for every network operation.
> >
> > Some notes:
> >
> >     - The scope of this library is limited to MySQL. Its value
> proposition
> >     is implementing the client protocol in an Asio-compliant way.
> Supporting
> >     any database other than MySQL is not in scope of this library.
> >     - This library does NOT make use of MySQL libmysqlclient C API. It
> >     provides a from-the-ground-up implementation of the MySQL client
> protocol.
>
> There is a MySQL++ library at https://tangentsoft.com/mysqlpp/home,
> which I have used in the past and found useful. How does your API
> compared to that library ?
>

   - The scope of the two libraries are inherently different. mysql++ is a
   C++ wrapper around libmysqlclient, and provides things like query building
   and connection pools. Boost.Mysql is an implementation of the MySQL client
   protocol, and thus provides an API to use that protocol. Boost.Mysql is a
   level of abstraction below mysql++ - it is at libmysqlclient level.
   - Boost.Mysql provides sync and async operations, both using Boost.Asio,
   and async operations follow Asio's universal async model, so you can use
   callbacks, Boost coroutines, C++20 coroutines or futures. mysql++ does not
   provide async functions because libmysqlclient doesn't do it, either.
   - Boost.Mysql provides access to server-side prepared statements, while
   I haven't seen the option in mysql++ (from having a quick look, their
   template queries seem to be handled client side). Server-side prepared
   statements are faster, more robust and more secure.
   - Boost.Mysql represents MySQL values as variants, allowing standard
   operations like visit. Each member if the variant is a vocabulary type
   (e.g. std::chrono::time_point/duration for datetimes/times,
   boost::string_view for strings...). mysql++ opts for custom types for
   strings, dates, times and datetimes. The mysqlpp::String type is kind of a
   variant type, also - it can be converted to any other mysqlpp type. This,
   however, closes the door for prepared statements, as the format the server
   uses is not string-based.
   - One nice thing about mysqlpp is that it provides the ability to parse
   rows into custom data structures. While Boost.Mysql can't do that at the
   moment, we will likely add the feature soon (using Boost.Describe if it
   gets into Boost).
   - Boost.Mysql is compatible with CMake and B2.

> I also looked at your mappings and very small database types are mapped
> to int64_t rather than smaller integers. Is there a reason for this, as
> it seems like a waste of space that should not be necessary ?
>

Values are stored as variants. Having more integer types means having more
options in the variant. This does two nasty effects:
- It increases user code complexity, as you have more options to consider.
- Visiting (which is used by both user code and the library itself) becomes
more expensive (the vtable ends up having more entries).

I don't think the performance gain you may get from using 1, 2 or 4 byte
integers (if any) is worth it, especially in 64 bit systems.

>
> I do like the fact that you are using asio for asynchronous handling and
> advance features above C++11 when compiling at a level higher than C++11.
>
> >
> > Features:
> >
> >     - Text queries and server-side prepared statements.
> >     - Sync and async functions, following Boost.Asio's universal async
> >     model. You may use callbacks, Boost coroutines, futures, C++20
> coroutines,
> >     or any completion handler that Asio adds support for.
> >     - Can be used with any Stream including TCP sockets, UNIX sockets and
> >     Boost.Beast TCP streams.
> >     - Supports MySQL 5.x, MySQL 8.x and MariaDB.
> >
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> >
>
>
>
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