Oops, I should had run the tests

When the adapter is with prepared statement disabled and the binds array
is not empty the connection adapter will try to set the binds values and
will fail. Now we are checking if the adapter has the prepared statement
disabled.

Fixes #12023

When mixing postgresql and another adapter like sqlite3 (for dev and test
respectively), the task `db:test:prepare` will fail due to the `enable_extension`
method not being defined in the abstract adapter. This patch simply adds an
empty definition to prevent it.

in favor of `begin_transaction`
with `:joinable` option.

removed two instances of add_column_options! from abstract_mysql_adapter

reworked rename_column_sql to remove add_column_options from schema_statements

changed to use new hash syntax.

added comments to test_invalid_type in sqlite3 adapter test and added valid_type? method to abstract_adapter.rb and removed unnecessary method from sqlite3 adapter

Adds support for algorithm option in MySQL indexes
Moves USING and algorithm options upstream

The syntax is still specific to the Adapter, so the actual executed string happens
in the corresponding adapter

We should only type cast when we need to use.

Related to 4b005fb3

This revision makes the terminology uniform with the rest of the file.
In general we describe these methods in terms of the adapter, rather
than the database. (As a side note, if we wanted to refer to the
database we would write "PostgreSQL".)

It was supposed to be removed by the preceding two reversions but I did
them in the wrong order.

This reverts commit 5d528f83.

Relates to f8c8ad56 which is also getting reverted due to failing test.

[ci skip]

add ActiveRecord::AbstractAdapter#extensions and ActiveRecord::ConnectionAdapters::PostgreSQLAdapter#extensions to allow dumping of enabled extensions to schema.rb, add ActiveRecord::SchemaDumper#extensions to dump extensions to schema.rb

* dependencies/autoload
* concern
* deprecation

It's sometimes hard to quickly find where deprecated call was performed, especially in case of migrating between Rails versions. So this is an attempt to improve the call stack part of the warning message by providing caller explicitly.

If your database supports setting the isolation level for a transaction,
you can set it like so:

  Post.transaction(isolation: :serializable) do
    # ...
  end

Valid isolation levels are:

* `:read_uncommitted`
* `:read_committed`
* `:repeatable_read`
* `:serializable`

You should consult the documentation for your database to understand the
semantics of these different levels:

* http://www.postgresql.org/docs/9.1/static/transaction-iso.html
* https://dev.mysql.com/doc/refman/5.0/en/set-transaction.html

An `ActiveRecord::TransactionIsolationError` will be raised if:

* The adapter does not support setting the isolation level
* You are joining an existing open transaction
* You are creating a nested (savepoint) transaction

The mysql, mysql2 and postgresql adapters support setting the
transaction isolation level. However, support is disabled for mysql
versions below 5, because they are affected by a bug
(http://bugs.mysql.com/bug.php?id=39170) which means the isolation level
gets persisted outside the transaction.

This avoids us having to manually increment and decrement it.