How to fix HSQLDB problem after attemping to upgrade from JIRA 6.1 to 7.1.4

[Greg Post]

Bonehead move - tried to upgrade from JIRA 6.1 directly to 7.1.4 (I did re-index, backup database, and disable several plug-ins prior to the 7.1.4 install). The install process completed without errors and received "Installation is completed" message. However, when attempting to launch JIRA 7.1.4 received HSQLDB related error with comment to install 7.0 to fix the database problem. Downloaded 7.0 installer but the installer cannot downgrade the 7.1.4 installation.

My JIRA install is for personal use and plan to stick with HSQLDB. Is a manual fix available? Other suggestions?

[Nic Brough -Adaptavist-]

No, there's no "downgrade" you can do on JIRA.  You need to go back to the backup you took and try 6.1 to 7.0.  However, have a look at the backups/export directory - the routine trys to take a backup before upgrade in most case, so you may have a backup there.

I can't recommend the use of HSQLDB for any data that you want to keep, as it can, and does, fail catastrophically without warning - you have to assume any hsqldb backed JIRA is going to die the next time you use it.