I work on an application that, thanks to Hibernate, supports multiple database systems. I am having a problem with the Oracle dialect (I tried Oracle10gDialect, Oracle9Dialect and OracleDialect, all with the same result) that causes serious performance issues in our application.

The issue is that the same code causes significantly different queries to fetch entities from the database (using Session.get()) when using Oracle vs. MySQL. With Oracle, it fetches many more relationships through 'left outer join' than with MySQL, causing each object to take between 6-10 times as long to load.

Our application uses 3.2.7.ga at the moment, but a quick test showed that the issue is there with 3.6.7.final as well.

I am not at liberty to post the mapping files, so before trying to create a test case for it, I would like to ask if anyone has ever seen anything like this, and if there is something I might be doing wrong, or if this is actually a bug.