Association between SQL and memory relations

[cutalion]

Association from sql relation to memory relation does not seem to work.

  config.relation(:companies) do # default adapter is sql
    schema(:companies, infer: true) do
      associations do
        belongs_to :market_data, foreign_key: :symbol, view: :capitalization, override: true
      end
    end
  end

  config.relation(:market_data, adapter: :memory) do
    # do we need schema?
    schema do
      attribute :symbol, ROM::Types::String
      attribute :cap, ROM::Types::String
    end

    def capitalization(_assoc, companies)
      MARKET.select do |company|
        companies.pluck(:symbol).include? company[:symbol]
      end
    end
  end

Full example

require 'rom'
require 'rom-repository'
require 'rom-sql'
require 'logger'
require 'pry'

gateways = {
default: [:sql, 'sqlite::memory'],
memory: [:memory]
}
rom = ROM.container(gateways) do |config|
sql = config.gateways[:default].connection

sql.create_table(:companies) do
  primary_key :id
  column :name, String
  column :symbol, String
end

config.relation(:companies) do
  schema(:companies, infer: true) do
    associations do
      belongs_to :market_data, foreign_key: :symbol, view: :capitalization, override: true
    end
  end
end

config.relation(:market_data, adapter: :memory) do
  # do we need schema?
  schema do
    attribute :symbol, ROM::Types::String
    attribute :cap, ROM::Types::String
  end

  def capitalization(_assoc, companies)
    MARKET.select do |company|
      companies.pluck(:symbol).include? company[:symbol]
    end
  end
end
end

companies = rom.relations[:companies]
companies.changeset(:create, [{ name: 'Google', symbol: 'GOOG' }]).commit
companies.changeset(:create, [{ name: 'Facebook', symbol: 'FB' }]).commit
companies.changeset(:create, [{ name: 'Apple', symbol: 'AAPL' }]).commit

# Our external source of market data
MARKET = [
{ symbol: 'FB',   cap: '518B' },
{ symbol: 'GOOG', cap: '754B' },
{ symbol: 'AAPL', cap: '895B' }
]

result = companies
       .where(symbol: ['FB', 'AAPL'])
       .combine(:market_data)

$ ruby sql_memory_combine.rb
/home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-sql-2.4.0/lib/rom/sql/associations/many_to_one.rb:15:in `call': undefined method `qualified' for #<ROM::Memory::Schema:0x00000003971910> (NoMethodError)
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-sql-2.4.0/lib/rom/sql/associations/many_to_one.rb:50:in `prepare'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:301:in `eager_load'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:290:in `node'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/support/memoizable.rb:47:in `block (2 levels) in define_memoizable_names!'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:271:in `block in nodes'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:268:in `each'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:268:in `reduce'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:268:in `nodes'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/relation.rb:252:in `combine'
	from /home/cutalion/.rvm/gems/ruby-2.4.1/gems/rom-core-4.1.2/lib/rom/support/memoizable.rb:47:in `block (2 levels) in define_memoizable_names!'
	from sql_memory_combine.rb:60:in `<main>'

Download example

[solnic]

This is clearly a bug. rom-sql assumes that the other schema must be qualified too. I'm not entirely sure how to solve it at the moment, but probably adding this interface to core wouldn't be such a bad idea. WDYT @flash-gordon ?

[cutalion]

I'm not sure it would make sense for other gateways/adapters (how do call all rom-whatever gems?)
What if we qualify schema right before calling it. In the ROM::SQL::Schema#call method?

[flash-gordon]

@solnic but we qualified schemas in rom-sql 2.0, I believe those .qualified calls aren't even needed. Specs from rom-sql and rom/repo passing

[solnic]

@flash-gordon I thought about it before 2.0 final was released, but I realized it would create an implicit requirement that associations can only work when relations are qualified, and you may end up with un-qualified attributes by a mistake...on the other hand, current auto-qualification in associations is...implicit behavior 😆 So, we could try removing it and test it out with real apps to make sure (at least we) don't have use cases where some code actually relies on auto-qualification in associations.

[ianks]

We ran into this issue as well. Kind of a bummer and now we are just going to move the yaml relation to sql

[solnic]

OK let's finally address it in 5.0 and rom-sql 3.0