Convert PG::Result to an Active Record model

Question

pg-ruby allows you to send multiple queries to the database in one shot, which helps minimize the number of trips made to the database:

results = []
conn.send_query('QUERY1;QUERY2;QUERY3')
conn.block
while result = conn.get_result
  results << result
end

Given that for any result I already know the Active Record model, what's the appropriate way to convert the result into models? Right now I'm doing the following:

fields = result.fields
models = result.values.map { |value_set| 
  Model.new(Hash[fields.zip(value_set)])
}

The problem with that method is that each of the Active Record objects don't appear to be #persisted? since they've been instantiated with .new.

Answer 1

I think what you want is the ActiveRecord::Base.instantiate method. It will correctly handle the new_record?/persisted? issue, as well as finding the correct class for single-table inheritance.

For example:

fields = result.fields
models = result.values.map { |value_set| 
  Model.instantiate(Hash[fields.zip(value_set)])
}

Answer 2

It's looks like a hack but anyway

fields = result.fields
models = result.values.map { |value_set| 
  hash = Hash[fields.zip(value_set)]
  model = Model.new(hash)
  # some attributes may not be assigned i.e. id, created_at and updated_at
  # in that case you can assign them manually:
  # model.id = hash["id"] 
  model.instance_variable_set :@new_record, false
  model
}