On 01/09/11 13:58, David Jordan wrote:
I have a related question. I assume SDB is based on SQL as the
database access language. TDB has its own triple store
representation, which I understand is much faster than SDB/RDBMS, but
has some limitations from an update concurrency standpoint.
At the moment yes, soon, no. Transactions (full blown disk-level
paranoia about crashes and recovery) are coming.
Current, TDB requires the application to do multiple-reader or single
writer locking.
Do both
SDB and TDB build on top of a common core interface? If one had a
non-SQL DBMS that potentially offered high performance, if this
common core interface exists, would it be an appropriate interface to
build an implementation to a non-SQL database? Or would making lots
of alterations to TDB be necessary?
SDB and TDB offer the Jena APIs. The only difefrence is how you get
hold of an initial dataset or model. After that, there is no difference.
One other question. If an application has a set of ontologies it
uses, some of which are large and never change, some of which do
require concurrent updates, can one have an application that opens a
model in TDB, then opens a model from SDB, then combine these two
models together? Would this allow one to take advantage of the TDB
high-performance for the read-only ontologies, while still getting
update capabilities for the ontologies in SDB?
Yes - that's possible but depending on how you want to combine models.
A dataset can have models from multiple storage subsystems. Or maybe
your usage can work with data in different datasets.
Do you have specific requirements you are trying to meet?
Andy
-----Original Message----- From: Andy Seaborne
[mailto:[email protected]] Sent: Thursday, September 01,
2011 3:37 AM To: [email protected] Subject: Re: Adding
support for MonetDB
Tobias,
To turn the question round - what unique features of MonetDB could be
exposed through SDB to yield a better RDf store?
The current design covers the current set of databases supported but
it's not fixed - maybe there is something especially useful in
MonetDB and maybe it needs an extension to the design. The design is
based on templating via all those classes (the instance for each
database is a small class). The SQL generator usually needs some
per-DB work because SQL databases aren't exactly very "standard".
Andy
On 25/08/11 21:28, Paolo Castagna wrote:
Hi Tobias, first of all, welcome on jena-users mailing list.
Tobias Willig wrote:
Hi everyone,
I like to add support for MonetDB in SDB and I have two
questions concerning this project:
1. How much effort it takes to add support for a new database
type?
It requires some effort. You need to add new Java classes and the
necessary tests.
Have you checked out the SDB sources yet?
If not:
svn co
https://svn.apache.org/repos/asf/incubator/jena/Jena2/SDB/trunk/
SDB cd SDB mvn test
You can use Eclipse and search for "Derby" which is one of the
DBMS supported by SDB. This way you'll find the list of Java
classes in SDB to support Derby. Then, you can read and study those
classes. While you do that, you'll learn the design of SDB and you
will get an idea on what it is required to add MonetDB.
2. Are there predefined extension points that allow adding a new
database type easily?
Yes, there are. Look at the super classes and interfaces from the
list of classes above (i.e. searching for "Derby").
There isn't an "how to add a new database to SDB" guide, however
make sure you read the general SDB documentation (it does not
hurt).
Also, if you want to contribute an "how to add a new database to
SDB" you are more than welcome to do so.
If so could you give me the name of some classes and config
files, which are important to accomplish that task?
You can start from:
GenerateSQLDerby -- extends --> GenrateSQL FormatterSimpleDerby
-- extends --> FormatterSimple StoreSimpleDerby -- extends -->
StoreBase1 FmtLayout2HashDerby -- extends --> FmtLayout2
StoreTriplesNodesHashDerby -- extends --> StoreBaseHash
TupleLoaderHashDerby -- extends --> TupleLoaderHashBase
FmtLayout2IndexDerby -- extends --> FmtLayout2HashDerby
StoreTriplesNodesIndexDerby -- extends --> StoreBaseIndex
TupleLoaderIndexDerby -- extends --> TupleLoaderIndexBase
Also look at:
- JDBC.java - DatabaseType.java - StoreFactory.java - SDB.java
And the existing tests.
May I ask you what motivates you in adding MonetDB?
I've never used it myself and, indeed, I use TDB instead of SDB.
Transactions are coming, hopefully in the 0.9.0 release of TDB.
Last but not least, it's not only about the code. You should be
willing to support the users of your code too. Once you add
support for MonetDB, people will start using it and, as they use
your code, they'll find bugs and they'll ask you for more features,
eventually. You should be willing to put some effort in fixing the
bugs, at least... and you can always say "no" politely to new
features. Until, someone else, who really needs the new feature and
he/she is willing to put some effort, will take over and push the
software a step further.
Once you start, you might have more specific questions on SDB
design. You can post your questions here or on
[email protected] mailing list. The more you
demonstrate you put some effort the more likely you'll receive
helpful answers back from the SDB developers. If you don't put
enough effort and expect others will do it for you, I am afraid,
you risk to have not much back.
To conclude, it you are motivated and you think you'll have fun
doing it (and you need it for your work): go ahead, it's not a
terribly huge task and it could be a nice contribution (in
particular for all the MonetDB users out there).
Paolo
Thanks in advance!
Best Regards Tobias Willig
