Thanks so much for the link on how to perform schemaless queries, it worked like a charm.
To add more context to your answer, according to the blog post, @jmurphyweb should probably do something like this instead.
def up do
offer_query = from(o in "offer", where: is_nil(o.regular_site_id), select: [id: o.id])
...
end
in the select be as specific as possible for the fields you need.
Hopefully, this will make it easier for anyone else down the line. Also here is a more up-to-date link to the same
