This reverts commit 55d9e494, reversing
changes made to 03e987cd.

Legacy mysql adapter is already removed in #22642.

Revert "Revert "Raise ConnectionNotEstablished rather than StatementInvalid in Mysql2Adapter#quote_string""

This reverts commit 6f92c40d.

This reverts commit 55d9e494, reversing
changes made to 03e987cd.

Legacy mysql adapter is already removed in #22642.

The `connection_config` method returns a `Hash`, but since we're moving
toward a place where we're using `DatabaseConfiguration::DatabaseConfig`
objects everywhere, we're introducing a new method here to replace it
called `connection_db_config`.
Co-authored-by: Neileencodes <eileencodes@gmail.com>

This commit renames `RoleManager` -> `PoolManager` and `Role` ->
`PoolConfig`.

Once we introduced the previous commit, and looking at the existing
code, it's clearer that `Role` and `RoleManager` are not the right names
for these.

Since this PR moves away from swapping the connection handler concepts
around and the role concept will continue existing on the handler level,
we need to rename this.

A `PoolConfig` holds a `connection_specification_name` (we may rename
this down the road), a `db_config`, a `schema_cache`, and a `pool`. It
does feel like `pool` could eventually hold all of these things instead
of having a `PoolConfig` object. This would remove one level of the
object graph and reduce complexity. For now I'm leaving this object to
keep the change churn low and will revisit later.
Co-authored-by: NJohn Crepezzi <seejohnrun@github.com>

In order to move schema_cache off of DatabaseConfiguration we needed to
make role accessible on pool.

While looking at `ConnectionSpecification`, `Role`, and `DatabaseConfig` John
and I noticed that this could be achieved by merging `ConnectionSpecification`
and `Role` into one `Role` class. This allows us to eliminate the `spec`
concept which is confusing. `spec` is a private method so renaming
to `resolve_role` is ok.

In the `Role` class we took `name` (renamed to `connection_specification_name`
for clarity since it's not a `role` name) and `db_config` from
`ConnectionSpecification` and the `pool` methods from `Role` and combined
them into one `Role` class.

This feels a lot cleaner to us because it clarifies the purposes of the
classes/methods/variables, and makes it easier to drop
`connection_specification_name` keyed on the parent class in the future.

There are a lot of changes in here but the majority of them are find and
replace `spec` -> `role`, `spec.name` ->
`role.connection_specification_name`, `Resolver#spec` ->
`Resolver#resolve_role`.

This PR also moves the `schema_cache` from `DatabaseConfig` to the new
combined `Role` class.
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>

This reverts commit 3420a145, reversing
changes made to afb66a5a.

When running Active Record MySQL test, this warning is printed in the
console:

    warning: instance variable errno not initialized

It turns out that this is a warning from `mysql` gem in MySQL::Error
object. However, since the `mysql` gem is no longer maintained, and
there won't be a newer version, it make sense for us to just silence
this warning to make the output cleaner.

I’m renaming all instances of `use_transcational_fixtures` to
`use_transactional_tests` and “transactional fixtures” to
“transactional tests”.

I’m deprecating `use_transactional_fixtures=`. So anyone who is
explicitly setting this will get a warning telling them to use
`use_transactional_tests=` instead.

I’m maintaining backwards compatibility—both forms will work.
`use_transactional_tests` will check to see if
`use_transactional_fixtures` is set and use that, otherwise it will use
itself. But because `use_transactional_tests` is a class attribute
(created with `class_attribute`) this requires a little bit of hoop
jumping. The writer method that `class_attribute` generates defines a
new reader method that return the value being set. Which means we can’t
set the default of `true` using `use_transactional_tests=` as was done
previously because that won’t take into account anyone using
`use_transactional_fixtures`. Instead I defined the reader method
manually and it checks `use_transactional_fixtures`. If it was set then
it should be used, otherwise it should return the default, which is
`true`. If someone uses `use_transactional_tests=` then it will
overwrite the backwards-compatible method with whatever they set.

Follow-Up to https://github.com/rails/rails/pull/14348

Ensure that SQLCounter.clear_log is called after each test.

This is a step to prevent side effects when running tests. This will allow us to run them in random order.

We can conditional define the tests depending on the adapter or
connection.

Lets keep the skip for fail tests that need to be fixed.

Clearly nobody uses this except me. It's fast people!