Re: [boost] Boost library submission (poll for interest)

Subject: Re: [boost] Boost library submission (poll for interest)
From: Rutger ter Borg (rutger_at_[hidden])
Date: 2010-01-08 10:39:27

Bob Walters wrote:

> I have a library I would like to submit for inclusion in Boost.  This
> message is just soliciting for interest per the submission process.
> If interest is expressed, I'll carry on with a preliminary submission.
> 
> The library is an embedded database, to the tune of products like the
> embedded version of InnoDB, BerkeleyDB, etc.  In this case, the
> database is structured as a Boost.interprocess shared region
> (typically mmap so it can page) which contains one or more STL-like
> containers holding application defined data types in directly usable
> form (i.e. not serialized.)  The database infrastructure is fully ACID
> compliant, with durability via write-ahead logging, and periodic
> checkpoints.  More details, examples, and documentation is available
> at http://stldb.sourceforge.net/ for more details on this libraries
> capabilities.
> 
> Currently, I've only implemented map<> (probably the most useful
> container type in a database), but the plan is to continue to add
> containers as requested/needed until ACID compliant versions of a
> decent portion of the STL are available.

Very interesting. I've written a std::map interface to Berkeley DB, which 
gives quite some of functionality. Taken from that, I have a couple of 
questions,

1) Transactional semantics: wouldn't it be easier to steal semantics from 
locks in threads? E.g., for the synchronous interface case, wouldn't

map_type m_map;
try {
  scoped_transaction trans( m_map );
  ..
  .. do stuff with the map
  ..
  trans.commit();
}
catch( transaction_error ) {
}

be a easier than passing the transaction everywhere?

2) what serialization models are you considering? I.e., for a map of int to 
doubles, serialization would be overkill, wouldn't it?

3) have you considered things like key prefix-compression and storing keys 
and values in different files?

4) how did you solve "map[ key ] = value" vs something = map[ key ]? Here, I 
resorted to a reference object that would do the .put() in case of 
assignment, a .get() in case of an implicit conversion.

5) do you reach 200,000 transactions per second per thread? :-)

What would be really nice is something like a stored version of multi_index.

Thanks,
Cheers,

Rutger