I recently encountered a small trouble on my TTRSS deployment.
It runs with a Percona Mysql backend.
When Percona pxc_strict_mode is enabled, DML operations are forbidden on tables without primary keys.
I did a little digging and found that thread in the old forums.
So I followed your recommendations here and made that pull request.
Please let me know if there is anything needing improvements or reformating.
i think this is best left outside of trunk.
in short: use postgres.
i've just noticed that you've also updated postgres schema file so point 1 can be ignored, i suppose.
Thanks for your quick reply.