SQL failed ... column "rev_parent_id" does not exist.
Now, it turns out that the revision table was added to MediaWiki in version 1.10.0, so it seems this was something broken since the upgrade to 1.10.0 back in November last year, but was only now being exposed. No doubt the issue has arisen because I insist on using PostgreSQL.
Anyway, I quickly consulted the relevant PostgreSQL schema, and fixed the problem by issuing the following SQL statement:
ALTER TABLE mediawiki.revision ADD COLUMN rev_parent_id INTEGER NULL;
There, easily fixed. Mind you though, it does annoy me that something like this happens every time I update MediaWiki - it's clear that Postgres just doesn't get the same level of testing that MySQL does by the MediaWiki project... maybe one of these days I should get off my butt, and actually help out ;)