thorough guide to Locks/Transactions/Isolation Levels in Rails [closed]

Question

Is there a good tutorial/guide/blog post/book chapter/screencast/etc that attempts to comprehensively cover everything having to do with locks, transactions, and isolation levels in ActiveRecord? (preferably relevant to Rails 4.0)

There's a brief section in the guides, and of course some API docs, but it's a really important and (for me) hard-to-understand domain, and it's my first time trying to take data integrity seriously in my Rails app. I'd like to get a good understanding so I can do it properly.

List of Known Resources

• http://guides.rubyonrails.org/active_record_querying.html#locking-records-for-update
• http://api.rubyonrails.org/classes/ActiveRecord/Locking/Optimistic.html
• http://api.rubyonrails.org/classes/ActiveRecord/Locking/Pessimistic.html
• http://api.rubyonrails.org/classes/ActiveRecord/Transactions.html
• https://github.com/rails/rails/commit/392eeecc11a291e406db927a18b75f41b2658253 ("Support for specifying transaction isolation level" commit -> Rails 4.0)
• http://railscasts.com/episodes/59-optimistic-locking-revised

Answer 1

I would check out Chapter 5 of The Rails 3 Way for now, particularly Section 5.5 on Database Locking. I would also look at the ActiveRecord::Locking source, ActiveRecord::Transactions source, and the transaction_isolation test case as the code is very readable and if you're going to need some down in the weeds answers, it's there in the code!

Answer 2

I found Differences between transactions and locking on Makandropedia a pretty useful starting point to learn the difference between transactions and locks.