Database Task Support

[metaskills]

Here are some notes I made while working on 4.2.

def truncate(table_name, name = nil)
  raise NotImplementedError
end

• Add a truncate method to the connection.
• The db:schema:load and db:structure:load no longer purge the database before loading the schema. This is left for the user to do. db:test:prepare will still purge the database. Closes #17945.
• Bring back db:test:prepare to synchronize the test database schema. Manual synchronization using bin/rake db:test:prepare is required when a migration is rolled-back, edited and reapplied. ActiveRecord::Base.maintain_test_schema now uses db:test:prepare to synchronize the schema. Plugins can use this task as a hook to provide custom behavior after the schema has been loaded. NOTE: test:prepare runs before the schema is synchronized.Fixes #17171, #15787.
• Add bin/rake db:purge task to empty the current database.
• No verbose backtrace by db:drop when database does not exist.
• Schema loading rake tasks (like db:schema:load and db:setup) maintain the database connection to the current environment.

[metaskills]

Tons of work in #351 cc @agios

[metaskills]

More work in #366

[metaskills]

Rather than pull in each PR, I learned from them and implemented something very similar. Thank you so much to both @agios and @bigtunacan for your work. Feedback on my commit is very much welcome. Here are my thoughts on the implementation.

• I am not a fan of the stubbed and mocked testing. Easily passing those tests did not ensure things actually worked. I crated a 4.1 test project (https://github.com/rails-sqlserver/ss_app) that smoke tested too. If you look at the new tests, you will see how they actually exercise the real code. And, it looks much much cleaner if you ask me.
• I even fixed a case where defncopy would report the length for a nvarchar as 8000 vs 4000.

[metaskills]

Also, I made structure_load just execute the SQL file. Much easier if you ask me.

[metaskills]

Real commit is here: 348361d

[rebelweb]

Will changes to the database tasks be able, to be backported to the adapter for 4.1.x? I am bound to SQL Server 2008 R2 for the time being, so I will be unable to upgrade to Rails 4.2 at this point.

[metaskills]

Yes, If someone were to make a comprehensive and tested PR to our 4-1-stable branch.