If you're using my backport of the 9.2 JSON feature in your 9.1 Postgres, you have a problem if you want to use pg_upgrade when moving to release 9.2: the type has the same name and behaviour in 9.1 as in 9.2, but the OIDs are different and so the upgrade will fail. If you use pg_dump/pg_restore, you should just be able to exclude the restoration of the extension and everything will "just work".
But after a lot of trial and error I have come up with a different way to do things. In this scenario we don't install as an extension, and instead we borrow a bit of magic from pg_upgrade to make sure that the JSON type and its array type have the same OIDs as they will have in PostgreSQL 9.2. We also need to fool pg_upgrade when it runs, as it goes looking for a loadable module called json.so, and of course in 9.,2 there isn't one because JSON is built in. So we need to supply a dummy one. But, given that, this too "just works".
There might be some wrinkles I haven't foreseen, but I have done this quite a few times now without mishap. This is checked in on a separate branch of the json_91 repo callled "binup"
If you are going to use this backport, I also highly recommend using the backport of the fix for missing column names on row expressions. This requires patching Postgres, but it's worth doing anyway, even if you're not using JSON - notably it affects some uses of hstore as well. You can get this by pulling the port into a git repo set at REL9_1_STABLE by doing:
But after a lot of trial and error I have come up with a different way to do things. In this scenario we don't install as an extension, and instead we borrow a bit of magic from pg_upgrade to make sure that the JSON type and its array type have the same OIDs as they will have in PostgreSQL 9.2. We also need to fool pg_upgrade when it runs, as it goes looking for a loadable module called json.so, and of course in 9.,2 there isn't one because JSON is built in. So we need to supply a dummy one. But, given that, this too "just works".
There might be some wrinkles I haven't foreseen, but I have done this quite a few times now without mishap. This is checked in on a separate branch of the json_91 repo callled "binup"
If you are going to use this backport, I also highly recommend using the backport of the fix for missing column names on row expressions. This requires patching Postgres, but it's worth doing anyway, even if you're not using JSON - notably it affects some uses of hstore as well. You can get this by pulling the port into a git repo set at REL9_1_STABLE by doing:
Enjoy.git pull https://bitbucket.org/adunstan/pgdevel.git rowexpr91