[Monetdb-developers] MAPI wire protocol?

Martin Kersten Martin.Kersten at cwi.nl
Wed Nov 7 08:06:23 CET 2007

Tim Gebhardt wrote:
> Hello,
Hello Tim,

thanks for your interest in MonetDB and your effort on the Windows platform.
We greatly appreciate it, because windows experts are a scarce resource in
a mostly Linux world.
> I'm working on a C#/.NET client library to connect to a MonetDB 
> server.  I've mapped most of the libMapi.dll api calls so that I can 
> call the C library from .NET but this presents a few problems:
> 1. There's a performance penalty to interface native code libraries to 
> .NET
> 2. There's a lot of overhead of marshaling UTF8 strings between .NET 
> and the C library, and potential problems with NULL parameters.
> 3. There's a portability problem with using the native libraries 
> (trouble deploying to the Mono runtime)
> I think the client library would be better off implementing the MAPI 
> wire protocol rather than interfacing with the C library, but I cannot 
> find any documents that detail the protocol.  Is there somewhere this 
> is published, or did I just not Google the right stuff?
The MAPI wire protocol has been developed and is used for a very long time,
way before XML became fashionable.  It is purposely in UTF8, for it greatly
simplified debugging, portability, interfacing,... Moreover, the same 
is used in all our APIs (php, python,java,perl,...) which eases maintenance.

We are aware of the corresponding overhead, but consider it less of  a 
knowing that most of the effect goes in communication itself and db core 

So, from our side we are first and foremost interested in the 1) and 3)
wrt your issues
1) does it amount to loading time only, or each call. And how bad is it?
2) what problems do you foresee with NULL parameters?
3) can you a bit more specific

regards, martin
> Also if anyone is interested in giving me a hand you can find the 
> Google Code workspace of the aforementioned project at this link: 
> http://code.google.com/p/monetdb-net/ 
> <http://code.google.com/p/monetdb-net/>
> -Tim Gebhardt
> tim at gebhardtcomputing.com <mailto:tim at gebhardtcomputing.com>
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