It behaves in the same way that the abstract adapter.

[ci skip]

test case for use singular table name if pluralize_table_names is setted as false while creating foreign key

refactor references foreign key addition tests

use singular table name while removing foreign key

merge foreign key singular table name methods

remove unnecessary drop table from test

`sql_runtime` was getting invoked even when the logger was set to fatal.
This ensures that does not happen by checking that the logger is set to
info level before logging the view runtime.

This reduces the number of times `sql_runtime` is called for integration
tests with a fatal logger from 6 to 2.

https://github.com/ruby/ruby/pull/579 - there is a new optimization
since ruby 2.2

Previously regexp patterns were faster (since a string was converted to
regexp underneath anyway). But now string patterns are faster and
better reflect the purpose.

  Benchmark.ips do |bm|
    bm.report('regexp') { 'this is ::a random string'.gsub(/::/, '/') }
    bm.report('string') { 'this is ::a random string'.gsub('::', '/') }
    bm.compare!
  end
  # string: 753724.4 i/s
  # regexp: 501443.1 i/s - 1.50x slower

- Eager loading was not working for the default_scope (class method)
  for 'find' & 'find_by' methods.
- Fixed these by adding a new check 'respond_to?(:default_scope)'.

    `widgets` table is being created in `primary_keys_test.rb` for PostgreSQLAdapter, MysqlAdapter, Mysql2Adapter
    and it makes test to fail earlier.

    Before:
      `bundle exec rake mysql2:test`

    ```
    Finished in 127.287669s, 35.5258 runs/s, 97.8885 assertions/s.

      1) Error:
    PersistenceTest::SaveTest#test_save_touch_false:
    ActiveModel::UnknownAttributeError: unknown attribute 'name' for #<Class:0x0000000a7d6ef0>.
        /home/kd/projects/kd-rails/activerecord/lib/active_record/attribute_assignment.rb:36:in `rescue in _assign_attribute'
        /home/kd/projects/kd-rails/activerecord/lib/active_record/attribute_assignment.rb:34:in `_assign_attribute'
        /home/kd/projects/kd-rails/activemodel/lib/active_model/attribute_assignment.rb:40:in `block in _assign_attributes'
        /home/kd/projects/kd-rails/activemodel/lib/active_model/attribute_assignment.rb:39:in `each'
        /home/kd/projects/kd-rails/activemodel/lib/active_model/attribute_assignment.rb:39:in `_assign_attributes'
        /home/kd/projects/kd-rails/activerecord/lib/active_record/attribute_assignment.rb:26:in `_assign_attributes'
        /home/kd/projects/kd-rails/activemodel/lib/active_model/attribute_assignment.rb:33:in `assign_attributes'
        /home/kd/projects/kd-rails/activerecord/lib/active_record/core.rb:293:in `initialize'
        /home/kd/projects/kd-rails/activerecord/lib/active_record/inheritance.rb:61:in `new'
        /home/kd/projects/kd-rails/activerecord/lib/active_record/inheritance.rb:61:in `new'
        /home/kd/projects/kd-rails/activerecord/lib/active_record/persistence.rb:50:in `create!'
        /home/kd/projects/kd-rails/activerecord/test/cases/persistence_test.rb:913:in `test_save_touch_false'

    4522 runs, 12460 assertions, 0 failures, 1 errors, 4 skips
    ```

    After:
      `bundle exec rake mysql2:test`

    ```
       Finished in 135.785086s, 33.3026 runs/s, 91.7774 assertions/s.

       4522 runs, 12462 assertions, 0 failures, 0 errors, 4 skips
    ```

Fixes #19568

We were never clearing the `PG::Result` object used to query the types
when the connection is first established. This would lead to a
potentially large amount of memory being retained for the life of the
connection.

Investigating this issue also revealed several low hanging fruit on the
performance of these methods, and the number of allocations has been
reduced by ~90%.

Fixes #19578

- ‘dection’ -> ‘detection’

- ‘exceeds threshold’ -> ‘exceeds the threshold’

- Other minor improvements.

When set to an integer, a warning will be logged whenever a result set
larger than the specified size is returned by a query. Fixes #16463

The warning is outputed a module which is prepended in an initializer,
so there will be no performance impact if
`config.active_record.warn_on_records_fetched_greater_than` is not set.

This obsoletes the ruby based implementations.

The type map was introduced in aafee233, but wasn't properly filled.

This mainly adjusts many locations, that expected strings instead of
integers or boolean.

add_pg_decoders is moved after setup of the StatementPool, because
execute_and_clear could potentially make use of it.

Ruby-pg's default way to serialize values for transmission to the database is to
call #to_s . This however creates a temporary String object for each value.
Setting a class based type map avoids the allocation of this additional String.

The performance benefit is measurable in microbenchmarks, but not with
the overhead of activerecord. However it's free to use and has no drawback.

This reverts commit 5cfa6a8a, reversing
changes made to bfd5bf83.

Reason: This broken travis build.

the newer method used for discriminating new records did not
use the older and more robust method used for instantiating
existing records, but did have a better post-check to ensure
the sublass was in the hierarchy. so move the descendants check
to find_sti_class, and then simply call find_sti_class from
subclass_from_attributes

This is obviously all very internal, but sometimes you have to look at
it... and when you do, it'll save a lot of confusion if it doesn't lie
about its identity.

The subtype will (quite reasonably) ignore the possibility that it has
`changed_in_place?` by becoming nil.

Fixes #19467

This is implemented in Type::Float, but not tested, so far.

association

While joining table of has_many :through association, ActiveRecord will
use the actual table name instead of through-join alias. It results with
a wrong SQL and exception is raised. This only happens when calculation
methods like #count is called.

This issue is affecting Rails 4.1.x and 4.2.x as well.

This reverts commit 796cab45.

As described here https://github.com/rails/rails/issues/19420. When
using the Postgres BigInt[] field type the big int value was not being
translated into schema.rb. This caused the field to become just a
regular integer field when building off of schema.rb. This fix will
address this by delegating the limit from the subtype to the Array type.

https://github.com/rails/rails/issues/19420

The code in the comment fails on concurrent inserts if done inside a transaction. 

The fix is to force a savepoint to run so that if the database raises an unique violation exception. Otherwise, you'll get errors like:

```
   (0.3ms)  BEGIN
  Cart Load (0.5ms)  SELECT  "carts".* FROM "carts"  WHERE "carts"."uuid" = '12345' LIMIT 1

# Another process inserts a cart with uuid of '12345' right now

  SQL (4371.7ms)  INSERT INTO "carts" ("created_at", "updated_at", "uuid") VALUES ('2015-03-21 01:05:07.833231', '2015-03-21 01:05:07.833231', '12345') RETURNING "id"  [["created_at", Sat, 21 Mar 2015 01:05:07 PDT -07:00], ["updated_at", Sat, 21 Mar 2015 01:05:07 PDT -07:00], ["uuid", "12345"]]
PG::UniqueViolation: ERROR:  duplicate key value violates unique constraint "carts_uuid_idx1"
DETAIL:  Key (uuid)=(12345) already exists.
: INSERT INTO "carts" ("created_at", "updated_at", "uuid") VALUES ('2015-03-21 01:05:07.833231', '2015-03-21 01:05:07.833231', '12345') RETURNING "id"

# Retrying the find

  Cart Load (0.8ms)  SELECT  "carts".* FROM "carts"  WHERE "carts"."uuid" = '12345' LIMIT 1
PG::InFailedSqlTransaction: ERROR:  current transaction is aborted, commands ignored until end of transaction block
: SELECT  "carts".* FROM "carts"  WHERE "carts"."uuid" = '12345' LIMIT 1
   (0.1ms)  ROLLBACK
ActiveRecord::StatementInvalid: PG::InFailedSqlTransaction: ERROR:  current transaction is aborted, commands ignored until end of transaction block
: SELECT  "carts".* FROM "carts"  WHERE "carts"."uuid" = '12345' LIMIT 1
```

Preserving RACK_ENV behavior.

This reverts commit 7bdc7635, reversing
changes made to 45786be5.

Fixes #19389.