[OJB-developers] ODMG transaction question

[Matt G. <mat...@ss...>]

Hi,

I have found something which I can only describe as strange, perhaps there
is a legitimate explanation or perhaps it's a bug.

First of all, some example code ...

Database schema:

    create table artist
    (
        id int not null,
        name varchar2(100),
        primary key (id),
        unique (name)
    )

Code:

    Transaction tx = odmg.newTransaction();
    tx.begin();

    Artist artist = new Artist();
    artist.name = "xyz";
    tx.lock(artist, Transaction.WRITE);
    tx.checkpoint();

    OQLQuery query = odmg.newOQLQuery();
    query.create("select allArtists from ojbtest.Artist");
    Collection list = (Collection) query.execute();
    Iterator it = list.iterator();
    while(it.hasNext())
    {
        artist = (Artist) it.next();
        System.out.println(artist);
    }

    tx.commit();

The 1st time the code is run the checkpoint commits the artist to the
database, as expected, and the "select allArtists" query returns the
expected rows.

The 2nd time through, the unique(name) constraint means that the artist
cannot be added but the checkpoint succeeds (!!!), the "select allArtists"
returns the same objects that were seen the 1st time and, finally, an
exception is thrown in tx.commit().

As a test I wrote almost the equivalent using the lower level OJB interface
and everything worked as expected i.e. an exception was thrown as soon as I
tried to add the same artist.

Is this the correct behaviour or is it a bug?

I have to say, I'm not sure I'd ever use transactions like this, it all came
about through some test code which *always* aborted the transaction. I
didn't have the checkpoint() then either. The intention was to leave the
database intact after running the test which addded data and then retrieved
it again - I was just playing with the API basically.

Cheers, Matt
---
Matt Goodall
Analyst Programmer, Strategic Systems Solutions
e: mat...@ss..., t: +44 113 3892645