[ci skip]

`IPAddr` is used in `OID::Cidr`.

Follow up to #23458.
Active Record supports MySQL >= 5.0 now.

Follow up to #24685. `insert_versions_sql` is not public API.

Make sure we handle explicitly passed nil's to lock_version as well.
An explicitly passed nil value is now converted to 0 on LockingType,
so that we don't end up with ActiveRecord::StaleObjectError in update record
optimistic locking

Fixes #24695

Re. 6e098284

https://github.com/rails/rails/commit/42dd2336b31a8d98776d039a2b9fd7f834156a78 changed INSERT INTO versions to run in 1 single query.
This breaks for sqlite versions < 3.7.11, which is especially the case on Ubuntu 12.04 LTS, that has SQLite version 3.7.9 as default.

So we check for support for multi insert, before performing single query inserts, else fallback to older version of running multiple queries.
[Vipul A M & Yasuo Honda]

When the query cache completes, if Active Record is still inside of a
transaction, it is because the transaction is meant to be left open
above this unit of work (such as transactional fixtures in tests). There
were several tests around the behavior of "tests" that were invalid, as
tests are not run through the executor. They have been changed to
reflect the new behavior, which is closer to what actually occurs in
Rails tests.

Fixes #23989
Fixes #24491
Close #24500

Follow up to #24221.

If the adapter supports indexes in create table, it generates SQL
in one query.

Follow up to 1683410c.

`Arel::Visitors::VISITORS` was removed at https://github.com/rails/arel/pull/412.

* Switch to keyword args where we can without breaking compat.
* Use add_table_options! for :options, too.
* Some code polish.

Don't create new arrays when trying to compute non_empty_predicates for where clause predicate. Get a 3-4% improvement in AST generation.
Perf compare: https://gist.github.com/vipulnsward/7e4e9ecb157e574002313249a7969c82

[ci skip] Update ActiveRecord associations documentation to avoid confusion with :validate option. Caused by #24532.

- Add link for finding the addional options for index.
- Add example for unique index as this is a common requirement.
- Add link in guide for index options.

Comments are specified in migrations, stored in database itself (in its schema),
and dumped into db/schema.rb file.

This allows to generate good documentation and explain columns and tables' purpose
to everyone from new developers to database administrators.

For PostgreSQL and MySQL only. SQLite does not support comments at the moment.

See docs for PostgreSQL: http://www.postgresql.org/docs/current/static/sql-comment.html
See docs for MySQL: http://dev.mysql.com/doc/refman/5.7/en/create-table.html

Follow up to #24542.

In MySQL and PostgreSQL, a time column value is saved as ignored the
date part of it. But in SQLite3, a time column value is saved as a string.

We should keep previous quoting behavior in sqlite3 adapter.

```
sqlite> CREATE TABLE "foos" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "start" time(0), "finish" time(4));
sqlite> INSERT INTO "foos" ("start", "finish") VALUES ('2000-01-01 12:30:00', '2000-01-01 12:30:00.999900');
sqlite> SELECT "foos".* FROM "foos";
1|2000-01-01 12:30:00|2000-01-01 12:30:00.999900
sqlite> SELECT  "foos".* FROM "foos" WHERE "foos"."start" = '2000-01-01 12:30:00' LIMIT 1;
1|2000-01-01 12:30:00|2000-01-01 12:30:00.999900
sqlite> SELECT  "foos".* FROM "foos" WHERE "foos"."start" = '12:30:00' LIMIT 1;
sqlite>
```

Context #24522.

TIME column on MariaDB doesn't ignore the date part of the string when
it coerces to time.

```
root@localhost [test] > CREATE TABLE `foos` (`id` int AUTO_INCREMENT PRIMARY KEY, `start` time(0), `finish` time(4)) ENGINE=InnoDB;
Query OK, 0 rows affected (0.02 sec)

root@localhost [test] > INSERT INTO `foos` (`start`, `finish`) VALUES ('2000-01-01 12:30:00', '2000-01-01 12:30:00.999900');
Query OK, 1 row affected, 2 warnings (0.00 sec)

Note (Code 1265): Data truncated for column 'start' at row 1
Note (Code 1265): Data truncated for column 'finish' at row 1
root@localhost [test] > SELECT `foos`.* FROM `foos`;
+----+----------+---------------+
| id | start    | finish        |
+----+----------+---------------+
|  1 | 12:30:00 | 12:30:00.9999 |
+----+----------+---------------+
1 row in set (0.00 sec)

root@localhost [test] > SELECT  `foos`.* FROM `foos` WHERE `foos`.`start` = '2000-01-01 12:30:00' LIMIT 1;
Empty set (0.00 sec)

root@localhost [test] > SELECT  `foos`.* FROM `foos` WHERE `foos`.`start` = '12:30:00' LIMIT 1;
+----+----------+---------------+
| id | start    | finish        |
+----+----------+---------------+
|  1 | 12:30:00 | 12:30:00.9999 |
+----+----------+---------------+
1 row in set (0.00 sec)
```

- Specify we want to run on latest stable ruby for mariadb

- change in runs of builds

Make mariadb? method publicly available

Previously we were assuming that the only valid types for encoding were
arrays and hashes. However, any JSON primitive is an accepted value by
both PG and MySQL.

This does involve a minor breaking change in the handling of `default`
in the schema dumper. This is easily worked around, as passing a
hash/array literal would have worked fine in previous versions of Rails.
However, because of this, I will not be backporting this to 4.2 or
earlier.

Fixes #24234

 Reason:
 - Its not publicly used method.
 - Exposing it makes an assumption that other adapters support it based on its usage - ActiveRecord::Base.connection.version

 [ci skip]

In 04ac5655 I assumed that we would
never want to pass the "table_name.column_name" form to where with a
symbol. However, in Ruby 2.2 and later, you can quote symbols using the
new hash syntax, so it's a semi-reasonable thing to do if we want to
support the dot notation (which I'd rather deprecate, but that would be
too painful of a migration).

Instead we've changed the definition of "this is a table name with a
dot" to when the value associated is a hash. It would make very little
sense to write `where("table_name.column_name": { foo: :bar })` in any
scenario (other than equality for a JSON column which we don't support
through `where` in this way).

Close #24514.

- we are ending sentences properly
- fixing of space issues
- fixed continuity issues in some sentences.

Reverts https://github.com/rails/rails/commit/8fc97d198ef31c1d7a4b9b849b96fc08a667fb02 .
This change reverts making sure we add '.' at end of deprecation sentences.
This is to keep sentences within Rails itself consistent and with a '.' at the end.

Rake includes (an extended version of) FileUtils in tasks.
It is more idiomatic that they use this provided interface.

- Check for protected environments while running `db:structure:load`
  similar to how `db:schema:load` behaves.
- Followup of https://github.com/rails/rails/pull/24399.

We support microsecond datetime precision for MySQL 5.6.4+. MariaDB has
supported it since 5.3.0, but even 10.x versions return a compatible
version string like `5.5.5-10.1.8-MariaDB-log` which we parse as 5.5.5,
before MySQL supported microsecond precision.

Specialize our version check to account for MariaDB to fix.

* Fix undefined method `owners' for NullPreloader:Class

Fixing undefined method `owners' for
ActiveRecord::Associations::Preloader::NullPreloader:Class

* Use Ruby 1.9 hash format

Use Ruby 1.9 hash format

#24192

[Rafael Mendonça França + Ladislav Smola]

The hard-coded back-ticks made it hard to use a different char for quoting db fields. This checkin replaces it with quote_table_name.