[LRUG] ActiveRecord::Relation#as_batches - like find_each but honours order, limit, offset

[Daniel Barlow]

An almost[*]-a-gem announcement, and a question:

The internet confirms that I'm not the only person who's attempted to
use find_each to get only part of a result set, and been disappointed
to find that it doesn't support order, limit or offset - any or all of
which might be useful if you want to consume a large but unknown
number of records without potentially instantiating several million
ActiveRecord::Base objects at once.  So  I wrote something that does.

ar-as-batches : https://github.com/telent/ar-as-batches/ lets you do e.g.

    User.where(country_id:
44).order(:joined_at).offset(200).as_batches do |user|
      user.party_all_night!
    end

and it works much as you'd expect

And now the question: to test it I create an in-memory sqlite database
and tell activerecord to log its sql queries to a Logger wrapping a
StringIO, then afterwards I match regexps on the string to see what
queries were actually sent.  I cannot help feeling that there must be
a Better Way: is there, and what?

https://github.com/telent/ar-as-batches/blob/master/test/as-batches-test.rb

This is the first time I've really done anything with ActiveRecord
innards, so all suggestions welcome


-dan

[*] "almost" meaning there's a gemspec in the repo and you can include
it with a :git entry in your Gemfile

-- 
dan at telent.net
http://ww.telent.net