Revert "ActiveRecord::Base#<=> has been removed.  Primary keys may not be in order," -- will be replaced with a check to ensure that the keys used for comparison are integers, and only fail if they are not.

This reverts commit 6256734e.

Conflicts:
	activerecord/CHANGELOG.md

Extend ActiveRecord::Base#cache_key to take an optional list of timestamp attributes of which the highest will be used.

Added ActiveRecord::Base#enum for declaring enum attributes where the values map to integers in the database, but can be queried by name

was using nullify strategy

This caused a regression in applications trying to upgrade.

Also if the user set the dependent option as destroy he expects to get
the records removed from the database.

Same as 4d4ff531

Same as 4d4ff531

Fixes: #12242, #9517, #10240

added schema_migrations_table_name to ActiveRecord::Base in order that the name of the schema migrations table can be configured.

consolidated test_schema_migrations_table_name tests

Added changelog entry

edited changelog

removed commented lines

removed reader

ensure the schema migrations table is reset at end of test

added entry to configuration guide

guides typo and changelog order

See also commit 5ac2341f

Raising `RuntimeErrors` skips important cleanup code and leads to
a lot of subsequent errors. This clutters the test output with a lot
of noise.

This is necessary because as of 5ac2341f `hstore` columns are always stored
as `Hash` with `String` keys. `ActiveRecord::Store` expected the attribute to
be an instance of `HashWithIndifferentAccess`, which led to the bug.

Currently they are all stored globally in the same `Hash`.
This commit forces the creation of a per-class variable if necessary.

The behavior was exposed through the following test-case:

```
  1) Failure:
StoreTest#test_all_stored_attributes_are_returned [/Users/senny/Projects/rails/activerecord/test/cases/store_test.rb:151]:
--- expected
+++ actual
@@ -1 +1 @@
-[:color, :homepage, :favorite_food]
+[:resolution, :color, :homepage, :favorite_food]
```

This is causing every default value in PostreSQL database to being
handled as default function.

Fixes #12581

Allows you to call #unscope on a relation with negative equality operators,
i.e. Arel::Nodes::NotIn and Arel::Nodes::NotEqual that have been generated
through the use of where.not.

Generated sub-query for Relation as array condition for `where` method
did not take in account its bind values, in result generates invalid SQL query.

Fixed by adding sub-query relation's binding values to base relation

Closes: #12586

`pluck` was updated to accept a list of columns, but the `NullRelation`
was never updated to match that signature. As a result, calling `pluck`
on a `NullRelation` results in an `ArgumentError`.