Hibernate ORM version 6.2.0.Final is around the corner, and the following post tries to shed some light
on one of the new features that comes with that release.
Supported database versions
For a long time, Hibernate kept around code for supporting database versions that are now considered ancient. It wasn’t always clear what the minimum database version is that is supposed to be supported and there was no continuous testing against old or the latest version of a database. The Hibernate team tried to support database versions on a best effort basis.
With Hibernate 6.0 the team wanted to do better and by making sure we commit ourselves to a certain set of DBs,
and move dialects for other DBs into a new module, called hibernate-community-dialects.
We provided clear requirements for vendors on how to get their dialects to hibernate-core.
Another thing that changed with Hibernate 6.0 is that dialects can now self-configure based on the database version, which eliminated the need for the various version specific dialects. There was still some overhead for dialect maintenance due to code that was trying to emulate certain functions or SQL constructs for ancient database versions. Since the Hibernate team is relatively small when considering the size of the project, we decided to clarify the supported set of databases in version 6.2 by also specifying versions which are supported. Doing so will make it easily understandable for users what Hibernate supports and what not. Additionally, it allows us to get rid of some code which makes maintenance easier.
As of version 6.2, every dialect will have a "minimum supported version" attached, and during self-configuration
of the dialect, it will check if the database version is greater or equal to that. If it isn’t, Hibernate emits a warning.
Dialects that support even older database versions were moved to the hibernate-community-dialects module
and are only updated on a best effort basis.
In general, Hibernate ties its database version support to the support cycle of the respective vendor. Minor versions of Hibernate might drop support for database versions that have become unsupported. The list of version support changes for Hibernate 6.2 can be nicely seen on HHH-15175
Outlook
Hibernate 6.3 will be the next minor version and as part of that, support for some more database versions will be dropped. The list of planned version support changes can be seen on HHH-15491.
I hope that this insight into the process of database version support is not a shocker to anyone. For the few people to which this is bad news, maybe this article helps you to justify a more continuous version upgrade.
