Sorry, got tangled up in this thing called 'real life'.
> If I understand you correctly, you want a prefix match, and sure there's
> a PostgreSQL extension for that:
OK, that seems to do the job, thanks a lot. The only small quibble is
that it's an extension.
I'm quite surprised there seem to be no way in core to treat an array as
an array. Using @> treats it as a set, AFAICT.