transaction.

move validation to AR

This implements the support to encode/decode JSON
data to/from database and creating columns of type
JSON using a native type [1] supported by PostgreSQL
from version 9.2.

[1] http://www.postgresql.org/docs/9.2/static/datatype-json.html

The previous implementation had the strange requirement that db/structure.sql contain only CREATE TABLE sql statements, one per table, separated by double newlines. SQLite3 and PostgreSQL database tasks, on the other hand, simply spawn 'sqlite3' and 'psql' binaries to load the file directly. The new implementation follows this and attempts to respect all current MySQL configuration settings.

The string_to_dummy_time method was blindly parsing the dummy time string
with Date._parse which returns a hash for the date part regardless
of whether the time part is an invalid time string.

I had to create a new table because I needed an STI table,
which does not have both a "type" and a "custom_type"

the test fails with:
  1) Error:
test_alt_becomes_works_with_sti(InheritanceTest):
NoMethodError: undefined method `type=' for #<Cabbage id: 1, name: "my cucumber", custom_type: "Cucumber">
    /Users/username/Projects/rails/activemodel/lib/active_model/attribute_methods.rb:432:in `method_missing'
    /Users/username/Projects/rails/activerecord/lib/active_record/attribute_methods.rb:100:in `method_missing'
    /Users/username/Projects/rails/activerecord/lib/active_record/persistence.rb:165:in `becomes'
    test/cases/inheritance_test.rb:134:in `test_becomes_works_with_sti'
    test/cases/inheritance_test.rb:140:in `test_alt_becomes_works_with_sti'

This is purely a performance optimisation.

See https://gist.github.com/3552829

This is a performance/GC optimisation.

In theory, this could be optimised by the implementation (last time I
checked, this would have no effect on JRuby). But in practise, this make
attribute access faster.

We don't need separate @class_to_pool and @connection_pool hashes.

* Loop rather than recurse in retrieve_connection_pool
* Key the hash by class rather than class name. This avoids creating
  unnecessary strings.

Per https://github.com/lifo/docrails/commit/e94e8d8c3fcac624466afcf61f6a118abe5a6af4#commitcomment-1784677

Thanks @randomecho!

This reverts commit e94e8d8c.

This reverts commit 7a8aee08.

This reverts commit a7f4b0a1.

Conflicts:
	activerecord/lib/active_record/associations/has_one_association.rb
	activerecord/lib/active_record/persistence.rb
	activerecord/test/cases/base_test.rb
	activerecord/test/cases/dirty_test.rb
	activerecord/test/cases/timestamp_test.rb

This functionality will be available from gem
`active_record-session_store` instead.

This is a cleaner version of #6916.

Closes #3165.

I've noticed a caveat with the :autosave option biting people before.
Questions arise about why they must explicitly save an associated object
in their own before_save callbacks. I've updated the documentation as
such to note to users that the :autosave callback occurs before any
user defined callbacks. They must save the associated record themselves
if altering it in their own callbacks.
Signed-off-by: NDavid Celis <david@davidcelis.com>

The new option allows any Ruby namespace to be registered and set
up for eager load. We are effectively exposing the structure existing
in Rails since v3.0 for all developers in order to make their applications
thread-safe and CoW friendly.

reset_counters() was crashing when there were multiple belongs_to associations with the same foreign key.

This closes #5200.

* Use each_key instead of generating intermediate keys array.
* Use each_with_object instead of inject to build hash.
* Use ternary to return instead of if + assignment.