A quick look at when ActiveRecord instantiates Ruby objects

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With regard to this twitter conversation:
https://twitter.com/PericlesTheo/status/601745115074420736

Hi Pericles,

This morning I took a quick look at how ActiveRecord converts the query result
back into Ruby objects.

Here’s where it happens:

https://github.com/rails/rails/blob/master/activerecord/lib/active_record/querying.rb#L38

- So when you execute some query, such as Person.first or whatever,
  ActiveRecord calls find_by_sql. (For some queries, such as Person.count, it
  will use a different code path).
- The SQL is actually executed by connection.select_all - this converts the sql
  Arel tree object into a string and sends it to the DB. It uses a different
  adapter based on which DB server you are using. This is what I talked about
  in the presentation.
- Then the ActiveRecord adapter for he DB you are using converts the actual
  query results into an array of ActiveRecord::Result objects.
- Once that is done and select_all returns, notice that ActiveRecord calls:

result_set.map { |record| instantiate(record, column_types) }

See:
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/querying.rb#L50

- This converts each result into the actual AR class from your Rails app.

Does that make sense?

Makes perfect sense! Thanks for taking the time to answer my question. Really appreciate it!