`Computer` class needs to be require

See #17217 for more details

Fixes #17170

Sufficiently large integers cause `find` and `find_by` to raise
`StatementInvalid` instead of `RecordNotFound` or just returning `nil`.
Given that we can't cast to `nil` for `Integer` like we would with junk
data for other types, we raise a `RangeError` instead, and rescue in
places where it would be highly unexpected to get an exception from
casting.

Fixes #17380

This method would assume that if last migration in the migrations
directory matched the current schema version, that the database was up
to date, but this does not account for new migrations with older
timestamps that may be pending.

As per discussion, this changes the model generators to specify
`null: false` for timestamp columns. A warning is now emitted if
`timestamps` is called without a `null` option specified, so we can
safely change the behavior when no option is specified in Rails 5.

The fixtures are still in play, adding a new column without a default and `null: true`
is not possible. This reverts back to leaking global state, as our `schema.rb` adds
the `null: false` constraint on this field.

A future solution would be to make the `migration_test.rb` run independent of fixture tables.
This way we can simply drop the state after test execution, without worrying about side effects.

/cc @zuhao

If we want to have type decorators mess with the attribute, but not the
column, we need to stop type casting on the column. Where possible, we
changed the tests to test the value of `column_defaults`, which is
public API. `Column#default` is not.

For consistency with https://github.com/rails/rails/pull/15557

Missed a case that only occured for mysql/mysql2

With ActiveRecord::Properties, we now have a reasonable path for users
to continue to keep this behavior if they want it. This is an edge case
that has added a lot of complexity to the code base.

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.

This makes the tests inside `migration_test.rb` order independent.
The assignments to `Reminder.table_name_prefix` and `Reminder.table_name_suffix`
previously leaked and had impact on following test cases.

This patch isolates the assignments on a throw-away subclass.

also override drop_table in AbstractMySQLAdapter to properly drop
temporary tables without committing the transaction

We can now make use of the existent #travel/#travel_to helper methods
added to AS test case and available in all tests.

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

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

Same as 4d4ff531

added schema_migrations_table_name to ActiveRecord::Base in order that the name of the schema migrations table can be configured.

consolidated test_schema_migrations_table_name tests

Added changelog entry

edited changelog

removed commented lines

removed reader

ensure the schema migrations table is reset at end of test

added entry to configuration guide

guides typo and changelog order

This prevents deprecation warnings from popping up.

The options will specify the prefix and the suffix. Also, I'm moving the
method to be an instance method on the +Migration+ instance. This makes more
sense than being a class method on the +Migrator+ class because the only
place that uses it is on a +Migration+ instance (in a method_missing
hook). The logic for the Migrator shouldn't be doing any work to
calculate the table name, it should be the Migration itself.

Also made some small indentation fixes.

This reverts commit 10259c3e.

reason: this causes rake test_mysql and test_mysql2 fail

If the order in which tests are executed is changed then test fails.
This commit ensures that all migrations are run before ensuring that
there are no pending migration.

During insertion of "# This migration comes from ... " comment at the beginning of
a migration, presence of magic comment was not considered.

schema_statements uses the column name by default to construct the index name, and then raises an exception if it doesn't exist, even if the name option is specified, which causes #8858.  this commit makes index_name_for_remove fall back to constructing the index name to remove based on the name option.

Closes #9483.

There are SQL Queries that can't run inside a transaction. Since
the Migrator used to wrap all Migrations inside a transaction there
was no way to run these queries within a migration.

This patch adds `self.disable_ddl_transaction!` to the migration to
turn transactions off when necessary.