also override drop_table in AbstractMySQLAdapter to properly drop
temporary tables without committing the transaction

* interpreted as a argument prefix

This will fix the [broken
test](https://github.com/rails/rails/commit/4a2650836680f51490e999c3c8441a2f9adff96e)
 `test_with_limiting_with_custom_select`.

The query's result was built in a hash with column name as key, if the
result have a duplicated column name the last value was
overriding the first one.

Add a bunch of Relation -> Array delegate methods to the whitelist. This won't last - aim to switch back to a blacklist for mutator methods.

calling replace_keys could possibly do a nil check twice, this commit
reduces it to once.

methods that call set_inverse_instance with a record will not have to
pay the cost of a nil check on every call

activerecord-deprecated_finders expects the parameters denormalized in
its initialize method

This is to get activerecord-deprecated_finders work again

It is needed for activerecord-depecated_finders

This reverts commit dcff027a, reversing
changes made to 3a209398.

It is need in activerecord-deprecated_finders

The dynamic finder was creating the method signature with the parameters name,
which may have reserved words and this way creating invalid Ruby code.

Closes: #13261

    Example:

        # Before
        Dog.find_by_alias('dog name')

        # Was creating this method
        def self.find_by_alias(alias, options = {})

        # After
        Dog.find_by_alias('dog name')

        # Will create this method
        def self.find_by_alias(_alias, options = {})

For PG adapters with custom expression and grouped result
of aggregate functions have not found correct column type
for it. Extract column type from query result.

Closes: #13230

Since MySQL 5.7.3 m13 does now allow primary key column is null.

Example: Given you have a comments model with a polymorphic commentable
association (e.g. books and songs) with the touch option set.
Every time you update a comment its commentable should be touched.
This was working when you changed attributes on the comment or when you
moved the comment from one book to another. However, it was not working
when moving a comment from a book to a song. This is now fixed.

Closes #7441

Closes #13146.

This fixes an error when using:

```
change_colum :table, :column, :bigint, array: true
```

Callback caller class uses `after_initialize`,
but Callback callee defines `after_find`.

Current sample code causes following error.

  NoMethodError: undefined method `after_initialize' for #<EncryptionWrapper:0x007fe4931fa5c0>

This commit takes into account the last cache_enabled value, before clearing query_cache.

Fixture files are passed through an ERB renderer before being read as
YAML. The rendering is currently done in the context of the main object,
so method definitons leak into other fixtures, and there is no clean
place to define fixture helpers.

After this commit, the ERB renderer will use a new subclass of
ActiveRecord::FixtureSet.context_class each time a fixture is rendered.