Introduce new ActiveRecord transaction error classes

[Erol]

Summary

This is a WIP follow-up to #25093.

I went ahead with @jeremy's recommendation of introducing ActiveRecord::TransactionRollbackError, with subclasses to distinguish between a serialization failure or deadlock.

Checked around, and it looks like MySQL is just returning an Error: 1213 SQLSTATE: 40001, whereas PostgreSQL tries to distinguish between serialization failures and deadlocks. Given the following test scenarios:

thread = Thread.new do
  Sample.transaction isolation: :serializable do
    Sample.delete_all

    10.times do |i|
      sleep 0.1

      Sample.create value: i
    end
  end
end

sleep 0.1

Sample.transaction isolation: :serializable do
  Sample.delete_all

  10.times do |i|
    sleep 0.1

    Sample.create value: i
  end
end

thread.join

s1 = Sample.create value: 1
s2 = Sample.create value: 2

thread = Thread.new do
  Sample.transaction do
    s1.lock!
    sleep 1
    s2.update_attributes value: 1
  end
end

sleep 0.5

Sample.transaction do
  s2.lock!
  sleep 1
  s1.update_attributes value: 2
end

thread.join

PostgreSQL returns 40001 for the first scenario and 40P01 for the second. MySQL returns 40001 for both.

Also checked MS SQL Server and Oracle and - like MySQL - they only have error mappings for 40001, which they use for serialization failures.

Other Information:

PostgreSQL: http://www.postgresql.org/docs/devel/static/errcodes-appendix.html
MySQL 5.7: https://dev.mysql.com/doc/refman/5.7/en/error-messages-server.html
MS SQL Server: https://msdn.microsoft.com/en-us/library/ms714687.aspx
Oracle Database 12c: https://docs.oracle.com/database/121/ZZMOD/appd.htm#ZZMOD338

[rails-bot]

r? @arthurnn

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[Erol]

r? @jeremy

[Erol]

Also did a quick check and it seems like the MS SQL Server adapter is only translating deadlock errors - which is also 40001 - via a custom ActiveRecord::DeadlockVictim exception. The Oracle Enhanced adapter does not translate any form of transaction errors at all.

@jeremy Your thoughts? Can we proceed with this current set of changes?

[Erol]

Just wanted to ask. Any feedback on this?

[rafaelfranca]

Perfect investigation. Thank you so much.