Optional identity columns

[brianthoman]

The goal here is to add optional support for Oracle 12's IDENTITY columns.

This code is probably still in need of some cleanup/adjustments, but I wanted to submit it as a sort of proof-of-concept and get some feedback before I continue working on it.

By default, IDENTITY columns are disabled. They can be enabled in the following ways:

For the whole app via initializer/config:

ActiveRecord::ConnectionAdapters::OracleEnhancedAdapter.use_identity_for_pk = true

In migrations:

create_table :things, primary_key_as_identity: true

# OR

create_table :things, id: false do |t|
  t.primary_key :test_id, :primary_key, identity: true
end

# OR

add_column :things, :test_id, :primary_key, identity: true

Please let me know what you think. Thank you!

[mattalat]

We would love this change. It also would solve https://github.com/rsim/oracle-enhanced/issues/2049.

[akostadinov]

If Rails can create proper relationships with the new column type, then I would say, use it by default unless user requested older style primary key. Or course some test cases to show that would be needed.

Another thing to consider is migrations and schema dumps with :ruby format. For migrations I don't know, but probably it makes sense to dump selecting old style PK for tables using old style.

In either case, thorough upgrade docs would be needed.

[mattalat]

@yahonda Sorry to ping directly, but I wonder if you have any reservations about this PR or any guidance on things to improve so it can be accepted. I would love to see this support make it into the gem.

[yahonda]

Let me have some review.