ref: 72c15572

- We must use `authors` fixture with `author_addresses` because of its foreign key constraint.
- Tests require PostgreSQL >= 9.4.2 because it had a bug about `ALTER CONSTRAINTS` and fixed in 9.4.2.

PG's type map assumes that all Ruby floats are going to a field with an
OID of type float4 or float8, and generates text which is invalid syntax
for other types. Since the gem can handle floats properly without this
encoder (albeit slightly slower), we can continue to use that as we have
in prior versions of Rails.

Fixes #27246

Since 9.4, PostgreSQL recommends using `pgcrypto`'s `gen_random_uuid()`
to generate version 4 UUIDs instead of the functions in the `uuid-ossp`
extension.

These changes uses the appropriate UUID function depending on the
underlying PostgreSQL server's version, while maintaining
`uuid_generate_v4()` in older migrations.

A query may wait on a database-level lock, which could lead to a
deadlock between threads.

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

All indentation was normalized by rubocop auto-correct at 80e66cc4.
But comments was still kept absolute position. This commit aligns
comments with method definitions for consistency.

There's no 'text to text' casting in the cast table so the feature detection fails.

There are some minor changes to the point type as I had forgotten that
this will affect the behavior of `t.point` in migrations and the schema
dumper so we need to handle those as well.

I'll say this again so I can convince myself to come up with a better
structure... TYPES SHOULD NOT CARE ABOUT SCHEMA DUMPING AND WE NEED TO
BETTER SEPARATE THESE.

For reduce instantiating `Type::Value`.

The current code base is not uniform. After some discussion,
we have chosen to go with double quotes by default.

Because `type_cast` against `binds` always requires
`attr.value_for_database` and this pattern appears frequently.

Address to https://github.com/rails/rails/commit/5a302bf553af0e6fedfc63299fc5cd6e79599ef3#commitcomment-18288388.

Follow up of 1683410c.
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

Example:

    create_table :users do |t|
      t.string :name
      t.index 'lower(name) varchar_pattern_ops'
    end

Fixes #19090.
Fixes #21765.
Fixes #21819.
Fixes #24359.
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

- Rename max to statement_limit
- Remove magic number 1000 from everywhere
- Defined StatementPool::DEFAULT_STATEMENT_LIMIT and started using it everywhere
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

Adapters override `#supports_savepoints?` to return `true` if they
support transaction savepoints. Defaults to `false`.

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

`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.

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 #24079

    p PostgreSQLAdapter::OID::Money.precision
    # => 19

    p PostgreSQLAdapter::OID::Money.new.precision
    # => nil

This reverts commit ff835f90, reversing
changes made to c4d85dfb.

Reason: This broke the tests. We will add back after investigated.

These methods are private and unused from anywhere.

The default 'now'::date is CURRENT_DATE.

This is useful to libraries that want to feature gate based on the
version of PostgreSQL the user is connected to. For instance, I want to
know if the user is connected to a version of Postgres that supports
concurrent materialized view refreshes. I could add that as a method on
the adapter as a PR, but rails has no need for this itself.

Rails is already using the postgresql_version for its own feature gating
and this makes that possible for other libraries.

Since the attributes API is new in Rails 5, we don't actually need to keep
the behavior of `attribute :point`, as it's not a breaking change.

`pool` in args is unused anymore. And `config` is used in all adapters.