We use postgreSQL but I have a question. 
Is it possible to make queries in order to retrieve data to make reports and stuff like this, or it will be more useful if I use an add-on ?

PostgreSQL 9.6 caused crashes in JIRA for me. I was able to load the latest postgresql JDBC driver from here: https://jdbc.postgresql.org/ by replacing the one in the <JIRA-DIR>/lib directory (postgresql-9.1-903.jdbc4-atlassian-hosted.jar) with postgresql-9.4.1212.jar and it is working. 

Thank you Daniel

OK, coming in 7.3

https://developer.atlassian.com/jiradev/latest-updates/preparing-for-jira-7-3

Andreas, it is of course nice to hear, that PostgreSQL 9.5 works for you (and I would not expect anything else). However in an Enterprise world I rely on support from Atlassian. And if Atlassian does not support that version yet, I do not migrate.

By the way, I think I was the one that triggered the creation of this issue. So I am still heavily interested to have the support for 9.5 or 9.6.

I need to create a new server for JIRA early next year because RHEL support for our current server stops. So I still hope I get a more recent version of Postgres supported by Atlassian when I have to build the new machine.

I believe this is what I pay licenses for....

And last thing. At this point I believe that JIRA is one of the few main Atlassian tools that don't support 9.5 yet (Confluence, Bitbucket, Bamboo already do).

And Postgres 9.6 is out since the end of September

https://www.postgresql.org/about/news/1703/

... but it is not listed yet as a supported database. Any statement from Atlassian about the ETA for this support?

We use Jira 7.1.8 with PostgreSQL 9.5 for nearly 3 weeks without any problems.