Use recursive common table expressions

[darenwelsh]

Ref:

• https://lists.wikimedia.org/pipermail/wikitech-l/2018-February/089565.html
• https://dbahire.com/mysql-8-0-new-features-in-real-life-applications-roles-and-recursive-ctes/
• https://mariadb.com/kb/en/library/recursive-common-table-expressions-overview/

This would require meza to upgrade MariaDB to include this feature.

[jamesmontalvo3]

Looks like this requires MariaDB 10.2.2 or greater. Meza currently is CentOS/RedHat version of MariaDB, which at present is 5.5.60. Meza could get MariaDB from the IUS repository (which is what it uses to get current versions of PHP and Python), but it looks like it only provides 10.0.x and 10.1.x at present [1]. At some point I'm sure it'll start providing 10.2.x. Looks like we could use the MariaDB repository itself [2].

[1] https://dl.iuscommunity.org/pub/ius/stable/CentOS/7/x86_64/repoview/applications.databases.group.html
[2] https://downloads.mariadb.org/mariadb/repositories/#mirror=accretive&distro=CentOS&distro_release=centos7-amd64--centos7&version=10.2