New serializer columns

[jwoertink]

Working with JSON::Any columns is kind of a pain. I have no idea how this would work, or what things we would run in to, but I had this idea that would look like this:

class User < BaseModel
  table do
    serialized preferences : PreferenceSerializer
  end
end

class PreferenceSerializer
  include JSON::Serializable

  property theme : String
  property font_size : String
end

user = UserQuery.first
user.preferences.theme #=> "dark"
user.preferences.font_size #=> "XL"

My initial thought was under the hood, it would look something like:

macro serialized(type_dec)
  column {{ type_dec.var }}_data : JSON::Any = JSON::Any.new({} of String => JSON::Any)

  def {{ type_dec.var }} : {{ type_dec.type }}
    {{ type_dec.type }}.from_json({{ type_dec.var }}_data.to_json)
  end
end

There's a lot of things to consider like how does this look in forms, how does it affect queries, or operations, etc... There's also the fact that it's a pretty big performance hit to convert a JSON::Any object in to a serialized object from JSON. It would be neat if Crystal had that built-in, but until that happens, we'd have to probably just make that as the downside to an easier to work with object.

I just wanted to jot down some ideas here, and keep track of it. If anyone has some thoughts, let me know.

[robacarp]

I'm doing something like that manually for json columns, along with a type column which indicates which "schema" the json column would conform to. My use case for the json column is that I didn't want to do have a bunch of null-able columns or try to wrangle any sort of inheritance model, so I need multiple possible schemas.

[matthewmcgarvey]

This is definitely connected to will/crystal-pg#125