[Monetdb-developers] About MonetDB's modules

Martin Kersten Martin.Kersten at cwi.nl
Wed Jun 1 18:02:05 CEST 2005


Hello,

A quick reply

Rodrigo Schmidt wrote:

> 
> Hello,
> 
> I am PhD student at EPFL, Switzerland, and I am working on database 
> replication. I just started looking at MonetDB and I have a simple 
> doubt. Are modules like the SQL module written in MIL or in C/C++?
Modules are mostly written in C, but they require more programming
experience than MIL. MIL is primarilly used to quickly produce code,
without all the worries you have when writing a C-based module.
> 
> I downloaded the sources of the SQL front end and I found some files 
> whose extension is ".mx" and which seem to implement the SQL translator 
> into MIL. The code looks pretty much like C++.
The SQL to MIL translator is written in C. The code and documentation
are packaged in 'mx' format, which supports combining code and 
documentation. The Mx tool is provided in the distribution.
> 
> Moreover, I read somewhere in your web page that two-phase-locking is 
> implemented outside the database kernel. Where exactly is it implemented 
> for the SQL front end?
It is handled in the catalog management area. Basically, the kernel
provides a module to implement locks and semaphores. However, the
relational algebra engine does not include these calls to separate the 
users, it is expected that the front-end compiler provides these calls.
This is in line with what some modern DBMS do.
> 
> Thank you very much in advance!
Success, keep us informed on your progress and findings.

Martin Kersten
> 
> Best regards,
> Rodrigo Schmidt
> 
> 
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