Hi,
today I've run for the first time in a couple of months
the versioning datastore unit test and found, to my dismay,
that lots of the were failing. I'm pretty sure I made
the versioning datastore work back after FOSS4G, yet
the issues I've found are pretty old so I'm confused...
Anyways, all the issue come down to the fact that
it's no more possible to the if an attribute was set
by the user code or not. This is due to a few
items in the feature type and feature creation code:
a) SimpleFeatureBuilder forces the default value on
all non nillable feature attributes, that is, if
the user did not provide a value, the default
is forced down the throat of the feature
b) AttributeImpl does verify that the attribute value
is valid on construction
a) seems like legitimate behaviour, but in fact imho it's
not. Picture this case: you have a table with a serial
primary key (auto-generated), and you want to include the
pk among the attributes (I need that for the versioning
to work and it's an option in the API anyways)
The feature gets built, the pk value is not provided,
as a result a default is stuck in. When it's time to
write on the db, the code sees the pk is already set,
so it does not try to generate it.
In fact I have a couple of places in versioning where
this occurs, and one in the text feature builder.
Now, I could make simple feature builder not force
in the defaults, but that would break right away
since the pk is not nillable so feature validation
will break. If I remove validation too
Besides the technical details of why versioning
does not work, I think that:
* it should be possible to build invalid features,
they have to be valid when saved, but not during
their life in memory
* if the user does not provide a value, none should
be forced into the feature, otherwise it becomes
impossible to say what was set, and what is not.
To recap, the current behaviour breaks a peculiar
code (one where the pk are mapped as attributes),
but I don't really know how to fix my code
without restoring the 2.4.x behaviour... I mean, I really
need to know if an attribute value was set or not,
and the current code makes it impossible to judge...
An alternative could be to mimic EMF, and provide
an isSet() method used to check if the value was actually
provided (and the value accessor can return the default
if a value was not provided, in that case).
Opinions?
Cheers
Andrea
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