Follow up to 99cf7558.

* Put a blank line after :call-seq: otherwise it will think the whole test
is the call seq.
* Improve some text.
* Use some rdoc formatting.
* Restores the documentation of table_name_prefix.

[ci skip]

[ci skip]

- These tests were fixed earlier on master in https://github.com/rails/rails/commit/f13ec72664fd13d33d617103ca964a7592295854.
- They started failing in first place due to change in https://github.com/brianmario/mysql2/commit/f14023fcfee9e85e6fc1b0e568048811518f8c23.
- They will fail again when the message is changed in mysql2 so let's
  not rely on the error message.

[ci skip]
Follow #26050

This reverts commit 671eb742.

This is not a change we would like moving forward.

- CollectionAssociation#select was removed in
  https://github.com/rails/rails/pull/25989 in favor of
  QueryMethods#select but it caused a regression when passing arguments
  to select and a block.
- This used to work earlier in Rails 4.2 and Rails 5. See gist
  https://gist.github.com/prathamesh-sonpatki/a7df922273473a77dfbc742a4be4b618.
- This commit restores the behavior of Rails 4.2 and Rails 5.0.0 to
  allow passing arguments and block at the same time but also deprecates
  it.
- Because, these arguments do not have any effect on the output of
  select when select is used with a block.
- Updated documentation to remove the example passing arguments and
  block at the same time to `CollectionProxy#select`.

Query cache doesn't type cast bind parameters since it isn't
actually querying the database, so it can't pass those values in.  Type
casting in the query cache method would cause the values to be type cast
twice in the case that there is a cache miss (since the methods it calls
will type cast *again*).  If logging is disabled, then adding the type
cast code to the query cache method will needlessly typecast the values
(since the only reason those values are type cast is for display in the
logs).

Fixes #26828.

This commit fixes the generated HTML of the two code examples.

Follow up to #20018.

MySQL 8.0.0-dmr `SUB_PART` column of `information_schema.statistics`
changed to varbinary(12), which is bigint(3) in MySQL 5.6.

Addresses #26774

If does not quote table name properly, invalid SQL is generated.

```
test/cases/adapters/postgresql/case_insensitive_test.rb:12: warning: ambiguous first argument; put parentheses or a space even after `/' operator
test/cases/adapters/postgresql/case_insensitive_test.rb:16: warning: ambiguous first argument; put parentheses or a space even after `/' operator
test/cases/adapters/postgresql/case_insensitive_test.rb:20: warning: ambiguous first argument; put parentheses or a space even after `/' operator
test/cases/adapters/postgresql/case_insensitive_test.rb:24: warning: ambiguous first argument; put parentheses or a space even after `/' operator
```

Follow up to #26735.

If `table_options` returns `{ comment: nil }`, `create_table` line is
broken.

Example:

```ruby
  create_table "accounts", force: :cascade,  do |t|
```

`migration_keys` includes `name` but `name` is not a column option.

```ruby
  # Before
  t.index ["firm_id", "type", "rating"], name: "company_index", order: {"rating"=>:desc}, using: :btree

  # After
  t.index ["firm_id", "type", "rating"], name: "company_index", order: { rating: :desc }, using: :btree
```

Currently blank comment does not dump to `db/schema.rb`. But created it
even if specified blank.

https://bugs.ruby-lang.org/issues/12739

ActiveModel::Type)

Some code was previously referring to ActiveModel::Type::*. This could
cause issues in the future if any of the ActiveRecord::Type classes were
overridden in the future.

`ActiveRecord::Type::Value`

This is now defined in
`ActiveModel::Type::Value` (`ActiveRecord::Type::Value` still exists but
it's effectively an alias)

Zlib is used to generate the advisory lock since commit 2c2a8755 .

Using the Migrator fails since then, when it is called without the rails context:

    NameError: uninitialized constant ActiveRecord::Migrator::Zlib

This patch fixes the above error.

We've seen occasional Travis failures mentioning deadlocks. I think
they're escaping from this test.

This was caused by 6d0d83a3. While the
bug it's trying to fix is handled if the association is loaded in an
after_(create|save) callback, it doesn't handle any cases that load the
association before the persistence takes place (validation, or before_*
filters). Instead of caring about the timing of persistence, we can just
ensure that we're not double adding the record instead.

The test from that commit actually broke, but it was not because the bug
has been re-introduced. It was because `Bulb` in our test suite is doing
funky things that look like STI but isn't STI, so equality comparison
didn't happen as the loaded model was of a different class.

Fixes #26661.

`test_native_decimal_insert_manual_vs_automatic` exists inside
`unless current_adapter?(:SQLite3Adapter)`. This condition is
duplicated.

This is not as good a solution as actually hashing both values, but Ruby
doesn't expose that capability other than allocating the array. Unless we were
to do something silly like have a thread local array that is re-used, I don't
see any other way to do this without allocation. This solution may not be
perfect, but it should reasonably avoid collisions to the extent that we need.

Per discussion in pull request #26622:

"Let's change it to PG::Error. The more specific classes mentioned are
subclasses, and the fact the raised exception is a PG::UndefinedColumn
doesn't change the fact that it's also a PG::Error." - matthewd