Oliver Elphick <olly@lfix.co.uk> writes:
> It will not be enough for the marker to list the path of the parent
> $PGDATA, since that path might get changed by system administration
> action. The marker should contain some sort of unique string which
> would match the same string somewhere in $PGDATA.
We have already added a notion of a "unique installation identifier"
for PITR purposes (look in pg_control). So we could use that for this
purpose if we wanted to.
But I'm not sure how important it really is. AFAICS the behavior of
CREATE TABLESPACE will be "create marker file, if it already exists
then abort". It has no need to actually look in the file and so there's
no need for the contents to be unique.
regards, tom lane