The Discourse README states that the minimum version of PostgreSQL is 9.1+. Judging from the rest of the documentation, the minimum should now be 9.2+. I’d submit a PR to fix this, but…
Backups created by Discourse include the statement
CREATE SCHEMA IF NOT EXISTS backup. Restores fail on PostgreSQL 9.2 because the
IF NOT EXISTS parameter for
CREATE SCHEMA was introduced in 9.3. Perhaps the minimum version should be documented as 9.3+ instead?