Re: [boost] [relational] Relational Model Library

From: Calum Grant (calum_at_[hidden])
Date: 2005-09-29 15:18:28

> [mailto:boost-bounces_at_[hidden]] On Behalf Of Andreas Pokorny
> On Wed, Sep 28, 2005 at 10:50:51PM +0100, Calum Grant 
> <calum_at_[hidden]> wrote:
> > > [mailto:boost-bounces_at_[hidden]] On Behalf Of 
> Andreas Pokorny 
> > > On Tue, Sep 27, 2005 at 09:24:24PM +0100, Calum Grant 
> > > <calum_at_[hidden]> wrote:
> > > > Is there any interest in providing relational 
> containers in Boost?
> > > > Are there any features/improvements you can suggest for RML?
> > > 
> > > You could compare the library with sqlite.
> > 
> > Completely different.  Most database engines are controlled 
> via text 
> > strings, and require parsing and data transformation.  This 
> cuts all 
> > that out using C++ templates, and is therefore way faster.  It's a 
> > container.
> 
> Oh, sorry my request was not formulated clearly enough. I 
> wanted to see how rml performs compared to sqlite in a 
> benchmark. Sqlite is currently 
> a nice and fast solution if you do not need a remote 
> database. Rml could 
> be an even better solution, if you do not require a text sql 
> interface, provided that there are table types available in 
> rml, which work without 
> being fully loaded to memory. 
> 
> 
> > > Furthermore you could implement a table that can be stored in
> > > a file, and used wihout reading all records into memory.
> > 
> > I think the memory-mapped file route would be the most 
> profitable, it 
> > would probably already work.
> 
> Interesting, could you give a short overview, how it could 
> already work.

You could use an allocator with RML (or indeed any STL container) that
stores the data in a memory-mapped file.  This basically makes the data
persistent.

I actually had a project a while back that did such a thing, and got
some good benchmarks comparing MySQL vs file-mapped containers:
http://lightwave.visula.org/persist/bench.html
and I'm sure boost::shmem::allocator is similar.  Performance is very
good.  We could devise a benchmark and I'll implement in RML +
Persist/Shmem, you implement in SQLlite and we'll see the difference. 

Calum