On 09/19/12 13:09, Caleb James DeLisle wrote:
On 09/15/2012 08:52 AM, Vincent Massol wrote:
Hi devs,
Just wanted to share my vision of how we should tackle migrating to the new
Model. I see the following steps:
* Step 1: Define new model interfaces (status: in progress)
We will probably need to revisit this step a number of times to get a really
compelling interface.
* Step 2: Implement a "bridged" version which uses the oldcore (status: in
progress).
* Step 3: Start moving code to use the new API as the new API and its
implementation progress. Note: we should start using the produce of step1 and
step2 ASAP to tune the details (status: not started)
* Step 4: At the same time, start a new implementation based on a RDBMS
(probably hibernate-based, to be decided) (status: not started). I'd also like
that we start other implementations not based on a RDBMS just to prove that it
works with other storages. Ideally I'd like some NoSQL impl (Caleb maybe?) and
I'd also like to try a Git-based implementation (using jgit)
* Step 5: Deprecate all our search apis located in XWikiHibernateStore and make
everyone use the new QueryManager module. This needs some tuning on the
QueryManager for missing stuff but that's doable (I need to send some proposal
on missing stuff). (status: in progress). The idea here is to decouple search
from storage. Note that we'll need to write some translator from HQL to XWQL or
the new search query language.
* Step 6: As we progress in step 2, 3, 4, introduce a configuration parameter to decide
which implementation to use ("bridged", etc) so that users can start playing
with new implementations (status: not started)
* Step 7: Rewrite a new Importer/Exporter that exports everything (all the data
in the current DB) + all configuration files/data. To see what we are currently
not exporting, see
http://platform.xwiki.org/xwiki/bin/view/AdminGuide/Backup#HUsingtheXWikiExportfeature
This new exporter should probably be based on the XWiki Streams module being
developed here: https://github.com/xwiki-contrib/wiki-stream (status: in
progress but not active)
* Step 8: When users want to migrate from one implementation ("bridged" for ex)
to a new implementation they export their wiki, set the new implementation in the
configuration file and reimport. (status: not started)
For me Step3 can almost begin (I probably need one or 2 more weeks to be ready
to have some use cases implemented and I'll send a vote to merge my work in
feature-newmodel branch in master - Would be good if you guys start looking at
it and give comments to be ready for this).
Then we need volunteer for Step 4 for:
* new RDBMS implementation. Who?
IMO we should do some kind of a cost/benefit analysis on different ORMs and
different schema options.
+1
I can share some of my experiences with DataNucleus/Cassandra which might help
us at least with designing a fast and scalable schema.
As a side note, if DataNucleus/RDBMS looks like a good option, we can reuse a
large amount of code from DN/Cassandra.
Of course implementing 2 out of 3 implementations with DataNucleus carries risk
of lock-in.
Yes and that would be the same if we go Hibernate/Hibernate OGM.
One thing to weight is which standard we use underneath. JPA seems to
have more active Open Source implementations, so that would mean a
stronger intermediary mapping layer that can potentially be shared for
multiple vendors (hibernate, DN, etc.). By opposition, there seems to be
only DataNucleus as a JDO 3 implementation, but it has the advantage to
be more thought out to be backed by any kind of datastore, and DN brings
a lot such implementations (though it does not support Cassandra, if we
decide to go for Cassandra, it means we support the DN/Cassandra plugin
ourselves).
* noSQL impl. Cassandra? other? Who?
Porting the existing DataNucleus/Cassandra implementation should be easy, it
stores generic user defined classes so it can represent basically anything.
* git implementation. Vincent
WDYT about the plan?
+1
Jerome
+1
Thanks,
Caleb
In term of time required it's probably going to take us about a year to have a
first working version for all the steps by working at a leisurely pace.
Thanks
-Vincent
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