How to append to a json column array in Rails 5.

example.rb

# assuming Model is your model and options is a json/jsonb column.
# This uses the Postgres json append || operator.
# And wraps the option inside an array.
# producing [{},{}] multiple hashes inside a top level json array.

# It is very important that the hash is [{}] NOT {} as not having the array on the 
# outside will cause the hash to replace the contents instead of appending to them.

new_option = [{
  name: option_name,
  time: Time.now.iso8601
}].to_json

Model.where(id: model.id).update_all(["options = options || ?::jsonb", new_option])

# Additional reading
# https://stackoverflow.com/questions/42233542/appending-pushing-and-removing-from-a-json-array-in-postgresql-9-5