A previous change made singleton methods eagerly define their relation
methods if it shared a name with a method on Kernel. This caused issues
with a few methods which were both defined on Kernel and on
AcitveRecord::Relation.

This commit avoids defining the method if it exists on AR::Relation.

Per [this discussion][arel-discussion] on the discourse forum, this is
an addition to Arel for supporting `@>` (contains) and `&&` (overlaps)
operators in PostgreSQL. They are useful for GIN-indexed data such as a
`jsonb` or array column.

  [arel-discussion]: https://discuss.rubyonrails.org/t/what-has-happened-to-arel/74383/51

`ReadOnlyTest#test_field_named_field` performs implicit commit the transaction by `ReadOnlyTest#setup`
because of the MySQL database behavior.

This commit addresses the failure at https://buildkite.com/rails/rails/builds/68962#68213887-1cef-4f76-9c95-aebc8799c806
Here are minimum steps to reproduce:

```ruby
% ARCONN=mysql2 bin/test test/cases/readonly_test.rb test/cases/dirty_test.rb test/cases/associations/inner_join_association_test.rb \
-n "/^(?:ReadOnlyTest#(?:test_has_many_with_through_is_not_implicitly_marked_readonly)|DirtyTest#(?:test_field_named_field)|InnerJoinAssociationTest#(?:test_eager_load_with_string_joins))$/" --seed 50855
Using mysql2
Run options: -n "/^(?:ReadOnlyTest#(?:test_has_many_with_through_is_not_implicitly_marked_readonly)|DirtyTest#(?:test_field_named_field)|InnerJoinAssociationTest#(?:test_eager_load_with_string_joins))$/" --seed 50855

..F

Failure:
InnerJoinAssociationTest#test_eager_load_with_string_joins [/Users/yahonda/src/github.com/rails/rails/activerecord/test/cases/associations/inner_join_association_test.rb:87]:
Expected: 3
  Actual: 4

bin/test test/cases/associations/inner_join_association_test.rb:82

Finished in 0.114674s, 26.1611 runs/s, 26.1611 assertions/s.
3 runs, 3 assertions, 1 failures, 0 errors, 0 skips
```

References:
- "13.3.3 Statements That Cause an Implicit Commit"
https://dev.mysql.com/doc/refman/8.0/en/implicit-commit.html

datetime with precision was passing assert_no_microsecond_precision
unintentionally, because `/\d\z/` is match to both datetime with
precision and datetime without precision. Fixed that by changing
time and regex to make it easier to grasp with and without precision.

Fix stub_version to consider schema_cache. ref: #35795

Remove failing test for unsupported version of MariaDB. ref: fb6743ac

Since MySQL 8.0.12, MySQL supports `ALGORITHM=INSTANT` DDL option.

https://dev.mysql.com/doc/refman/8.0/en/innodb-online-ddl-operations.html#online-ddl-index-operations

Follow up of #34122.

Relation method call is relying on method_missing, but if `Kernel` has
the same named method (e.g. `open`, etc), it will invoke Kernel's method
since method_missing is not happened.

To prevent that, eager generate relation methods if a method is the same
name on `Kernel`.

Fixes #39195.

`singleton_class` is in Ruby 1.9.2, and there is no use singleton class
eval in the files.

Current SQL generation code is hard to maintenance, I've found a bug
that create index comment in bulk change table when I'm refactoring
that.

I've found the bug when I'm refactoring index creation code in #39203.

We fixed `generate_relation_method` to address kwargs warnings at
#38038, but I missed generated named scopes also need the same fix.

Test case has picked from #39196.
Co-authored-by: NJohn Hawthorn <john@hawthorn.email>

We now always use `arel_attribute` for attribute alias resolution.

Positional hash argument should not be dup-ed.

Fixes #39170.

#39170 is a regression caused by 362348b5 to maintain kwargs flag to
address kwargs warnings.

Actually that result is odd and hard to predictable result to me, but we
should not change the public behavior without deprecation cycle.

I had not intended to break any apps, so I've restored the behavior.

Fixes #39171.

It is possible to unscope only the column in the specified table.

```ruby
posts = Post.joins(:comments).group(:"posts.hidden")
posts = posts.where("posts.hidden": false, "comments.hidden": false)

posts.count
# => { false => 10 }

# unscope both hidden columns
posts.unscope(where: :hidden).count
# => { false => 11, true => 1 }

# unscope only comments.hidden column
posts.unscope(where: :"comments.hidden").count
# => { false => 11 }
```
Co-authored-by: NSlava Korolev <korolvs@gmail.com>

Follow-up to #39147 and #39168.

By adding a new purpose-specific format, we avoid potential pitfalls
from concatenating format strings.  We also save a String allocation per
Time attribute per inspect.

The new format also includes a time zone offset for more introspective
inspection.

DATE_FORMATS can be either a format string or a lambda we don't want to attempt to concat them with a string if we are in the lambda case

In the AR test suite require_dependency does not make much sense. Just
call vanilla require/load.

Note that in the test that made explicit use of it, there are no
autoload paths, and no constants have been autoloaded. In reality, the
code ended up calling Kernel#load.

This removes an optimization that `attr.in(range_object)` acts as
`attr.between(range_object` which is deprecated over 5 years ago.

`attr.in` will generate exactly IN clause even if a range object is
passed. Use `attr.between` instead if BETWEEN clause is what want to
get.

Ref https://github.com/rails/arel/pull/333.

Any missing thing would be found such like #39159.

Some apps would expect that type cast is not evaluated at relation build
time consistently.

Context:

https://github.com/kamipo/rails/commit/b571c4f3f2811b5d3dc8b005707cf8c353abdf03#r31015008
https://github.com/rails/rails/pull/34303

And also this removes extra grouping on IN clause behaved as before.

SQLite3 does not recognize paths as file URIs unless the
`SQLite3::Constants::Open::URI` flag is set.  Therefore, without this
flag, a path like "file::memory:" is interpreted as a filename, causing
a "file::memory:" file to be created and used as the database.  Most
tests in `SQLite3TransactionTest` picked up this flag from
`shared_cache_flags`, but a few did not.  Because those tests were
creating a file, the path was changed in #38620 such that it no longer
pointed to an in-memory database.

This commit restores the database path as "file::memory:" and ensures
the URI flag is set whenever `in_memory_db?` is true.

Fixes #39073

This reverts commit 9817d74f, reversing
changes made to d326b029.

Just making this easier to merge our PR in. Otherwise there's tons of
conflicts and our PR is faster.

https://github.com/rails/rails/commit/5e0ef9ca7abb85343bc9dc3436350b91eb37ce01
https://github.com/rails/rails/commit/dd1aa7388990509796065d4cd19534d4017b42bc
https://github.com/rails/rails/commit/ea791e53f9edbe1e2d2ca779f5ce20b27320581f

Some commits adds `**` to address kwargs warnings in Ruby 2.7, but
`save` and `save!` are originally doesn't take positional arguments, so
maintain both `*` and `**` is redundant.

https://github.com/rails/rails/commit/6d68bb5f695414b1801c1c3952ef955a5b0b6c6a
https://github.com/rails/rails/commit/09d7ce79750d08b6b9c64fd038eee285d0cbfd44
https://github.com/rails/rails/commit/51a7422c9f10cc75a3ef6bf9177324fc771d7ba4

In the past, we sometimes hit missing `Symbol#start_with?` and
`Symbol#end_with?`.

https://github.com/rails/rails/commit/63256bc5d7dd77b2cce82df46c53249dab2dc2a8
https://github.com/rails/rails/commit/a8e812964d711fa03843e76ae50f5ff81cdc9e00

So I proposed `Symbol#start_with?` and `Symbol#end_with?` to allow duck
typing that methods for String and Symbol, then now it is available in
Ruby 2.7.

https://bugs.ruby-lang.org/issues/16348

Using `String#starts_with?` and `String#ends_with?` could not be gained
that conveniency, so it is preferable to not use these in the future.

```ruby
steve = Person.find_by(name: "Steve")
david = Author.find_by(name: "David")

relation = Essay.where(writer: steve)

# Before
relation.rewhere(writer: david).to_a # => []

# After
relation.rewhere(writer: david).to_a # => [david]
```

For now `rewhere` only works for truly column names, doesn't work for
alias attributes, nested conditions, associations.

To fix that, need to build new where clause first, and then get
attribute names from new where clause.

To change a NOT NULL constraint `reversible`.

When changing a NOT NULL constraint, we use `ActiveRecord::ConnectionAdapters::SchemaStatements#change` method that is not reversible, so `up` and `down` methods were required. Actually, we can use `change_column_null` method if only one constraint changed, but if we want to change multiple constarints with ALTER QUERY, `up` and `down` methods were required.

This is a remnant of the auto-explain feature, which was removed in
d3688e02.

Example failure: https://buildkite.com/rails/rails/builds/68661#84f8790a-fc9e-42ef-a7fb-5bd15a489de8/1002-1012

The failing `destroyed_by_association` tests create an author (a
DestroyByParentAuthor) and a book (a DestroyByParentBook) that belongs
to that author.  If the database already contains books that refer to
that author's ID from previous tests (i.e. tests that disabled
`use_transactional_tests`), then one of those books will be loaded and
destroyed instead of the intended DestroyByParentBook book.

By loading the `:books` fixtures, we ensure the database does not
contain such unexpected books.
Co-authored-by: NEugene Kenny <elkenny@gmail.com>
Co-authored-by: NRyuta Kamizono <kamipo@gmail.com>

before
```
p Knot.create
=> #<Knot id: 1, created_at: "2016-05-05 01:29:47">
```

after
```
p Knot.create
=> #<Knot id: 1, created_at: "2016-05-05 01:29:47.116928000">
```

https://buildkite.com/rails/rails/builds/68645#ebd598f6-fe4c-4273-b1a9-c78055f21874/1016-1027