Should I default jsonb to '{}' or {} in migration

In the migration file, you're going to want to use the {} vs '{}'.

I literally just was struggling this for a while, and the thing is is that I think the PG adapter implicitly knows how to convert a hash to a jsonb object. It's not like the json type in the postgres DB, where you're storing a string value of a json object, but an actual binary object (in jsonb). I can probably dig it up in the Rails 4.2 release code somewhere, but, if you're looking that the thin documentation on it (which I'm going to be adding to in the near future), the key here is that you're actually getting a string back from Postgres when you do '{}', and thus when you try to indifferent_access it, it fails, because a string can't have indifferent access. That was probably my first headsup that there was a few issues with the info they were providing.

I honestly don't use the straight up {} anyhow, favoring [] over {}, because usually I'm handling very specific logging functionality I want explicit on a record without having to join two large tables together. That's my particular use case here on 5.0, and it might be a bit different if you're <5, but probably not by much.

Just run a migration with the following:

add_column :ref_check_ins, :document, :jsonb, default: {}