[Geotools-devel] VersioningFeatureStore api

[Walter D. <wal...@gm...>]

Hello Devs,

My name is Walter and I work with LISAsoft with Jody. We are looking at
developing a system that uses feature versioning. Jody asked me to look into
creating a proposal for a VersionedFeatureStore api and I am trying to learn
the process for doing this properly. I have had a look at the code base a
bit and am still familiarising myself with it and have had a bit of a look
at the old versioned postgis module that is being removed. I had a bit of a
poke around to see about updating to the new classes and ran into a few
issues. The new JDBC api's are quite different from the old especially with
the fact that the DataStore is declared final. So the old process that was
used is very difficult to port of because of the reliance on the datastore
in the other classes.  I see 2 possible options at first glance to approach
the issue:

1 remove the use of final from datastore class. (Which seems to go against
the direction of the new API's)
2 change the api of Datastore to understand versioning and have
isVersioned() methods and throw UnsupportedOperationExceptions when a
versioned method is called. Any of the other changes then could be added to
the SqlDialect subclass.

The second option is kind of a fundemental change in that it assumes that
versioning is kind of a first class concern which kind of makesense in the
longterm as api's mature. It paves the way for an easier update of the
versioned PostGIS also to the new api.

Jody had defined this as VersioningFeatureStore api but is there also a
reason to implement a VersioningFeatureSource? For read only operations of
the history.

I imagine the api will be kind of light at the beginning and similar to
andrea's original efforts.
getLog((version1, version2 filter,users, count)
getDifferences(version1, version2 [filter])
getVersion(string)
getVersions()

There might be a completely different approach that someone has in mind
please let me know any suggestions.

Thanks,
Walter