Closes #14841.

This file is using this pattern already

Fixes #14752

Select mimics the block interface of arrays, but does not mock the
block interface for select!. This change moves the api to be a
private method, _select!.

`warning: ambiguous first argument; put parentheses or even spaces`

Also add a Changelog entry

[related #9702]
[fixes #8928]

So that irregular multi-word pluralization rules have to be defined only for snake-case strings.

Optimize select_value, select_values, select_rows and dry up checking whether to exec with cache for Postgresql adapter

Reduces creating unused objects, with the most dramatic reduction in select_values which used to map(&:first) an array of single element arrays.

* This is a follow up to: fe4b0eee
* The originating PR is #14222
* It should fix the build

Changed the NullRelation so that when count is called with #group it will properly return an empty hash instead of zero. Fixes issue #14721

Conflicts:
	activerecord/CHANGELOG.md

Closes #14222.

This is a follow up to #6104

This does not have the backwards compatibility issues brought up in
implementation to break.

Changed change_column in PG schema_statements.rb to make sure that the uuid_generate function was not being quoted.

`reaping_frequency` is used in Active Record `reap_frequency` is not

rather than YAML.load(File.read(path)). YAML.load_file is also used in
guides/rails_guides/helper.rb since 2011, the only other precedent I could find.

968c581e have fixed the EagerLoadTest, but
not in the correct way.

The problem was when `empty?` or `size` was called on relation. It was
triggering `count(:all)`, which was passing `:all` as the column name to `count`
on Calculations.

On the other hand, the method `calculate` on Calculations was calling
`construct_relation_for_association_calculations` instead of `perform_calculation`,
because `has_include?` was returning `true` since `column_name` was present.

To prevent calling the wrong method to perform the calculation, we have to check
if the `column_name` is present and if it is different from `:all` (which is now used
to correctly do `count` with `select`).

More information here: https://github.com/rails/rails/commit/968c581ea34b5236af14805e6a77913b1cb36238#commitcomment-6006135

968c581e have introduced this bug #14744
on Association Relation when the method `empty?` or `size` was called.

Example:
  # Given an author that does have 3 posts, but none of them with the
  # title 'Some Title'
  Author.last.posts.where(title: 'Some Title').size
  # => 3

It was occurring, because the Association Relation had implemented these
methods based on `@association`, this way giving wrong results.

To fix it, was necessary to remove the methods `empty?` and `size` from
Association Relation. It just have to use these methods from Relation.

Example:
  # Given an author that does have 3 posts, but none of them with the
  # title 'Some Title'
  Author.last.posts.where(title: 'Some Title').size
  # => 0
  # Now it will return the correct value.

Fixes #14744.

The second argument to serialize has double meaning:
  * `class_name` of the Type to serialize
  * `coder` to use then serializing.

The new variable name and the docs better describe that behavior.

Follow up to af549a1a

we're guaranteed to pass a numeric value for offset, so if it's zero,
just don't add an offset to the query

consistent.