[simon2Q]

Postgres-R is dead. No need to look.

Postgres-XC has never implemented multi-master, so don't look there. Postgres-XZ, if it exists, is a closed-source fork of XC by a Chinese company.

Postgres-XL implements cluster scaling for queries and transactions. It is alive and well. http://blog.2ndquadrant.com/when-to-use-postgres-bdr-or-post...

X2 is the developers of XL and XC working together to see if we can help each other; there is no separate code from that initiative.