[Mulgara-general] My job, and SPARQL development

Life is hard, and then you die ronald at innovation.ch
Wed Feb 6 00:46:42 UTC 2008


On Tue, Feb 05, 2008 at 12:58:39PM -0500, Brian Sletten wrote:
[snip]
> One other development that Paul and I have discussed off-list is  
> creating a more embeddable instance that will be easier to embed. We  
> are hoping to get rid of a lot of the RMI cruft and streamline how the  
> Mulgara engine can be used, accessed, etc.

We've been running mulgara as an embedded instance for a couple months
now, so I thought I'd mention how well/badly it works for us.

The RMI is not a problem, since we just create a local
DatabaseSession. What is ugly is the lack of model-name uri/url
disambiguation (ticket #58), though it's not a big problem for us
_yet_ as we aren't yet running the same code on embedded as well as
on remote instances,

However, there are decidedly ugly things in the whole SessionFactory
stuff, including SessionFactoryFinder and LocalSessionFactory (in fact
I think that part needs some serious rework), so that I've ended up
just copying out parts of code from those to create the
DatabaseSession instance. So this part could be significantly
improved.

Another problem is the assumption in various places of only a single
mulgara instance. If you think of libraries embedding mulgara for
internal use then it would be really nice if multiple instances could
be running in the same JVM and classloader (separate classloaders can
already be made to work). I've found two main places that need fixing
here: the above mentioned session-factory stuff, but I've also found
the use of static fields (singletons) in things like the
XANodePoolFactory which end up preventing one from being able to run
multiple instances.

We've also tried creating in-memory embedded mulgara instances, but a
bunch of things are not implemented there so we've found this not to
be usable (e.g. searching for typed-literals is not implemented in the
memory-based string-pool, leading to all sorts of things bailing out).

Anyway, I just thought I'd note some things that we noticed along the
way.


  Cheers,

  Ronald




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