This obsoletes the ruby based implementations.

The type map was introduced in aafee233, but wasn't properly filled.

This mainly adjusts many locations, that expected strings instead of
integers or boolean.

add_pg_decoders is moved after setup of the StatementPool, because
execute_and_clear could potentially make use of it.

Ruby-pg's default way to serialize values for transmission to the database is to
call #to_s . This however creates a temporary String object for each value.
Setting a class based type map avoids the allocation of this additional String.

The performance benefit is measurable in microbenchmarks, but not with
the overhead of activerecord. However it's free to use and has no drawback.

Versions of the pg gem earlier than 0.18.0 cannot be used safely with Ruby 2.2.
Specifically, pg 0.17 when used with Ruby 2.2 has a known bug that causes
random bits to be added to the end of strings. Further explanation here:
https://bitbucket.org/ged/ruby-pg/issue/210/crazy-bytes-being-added-to-record

The cause by which the test suite for the mysql adapter broke in 1502caef
(reverted 89ba5bb4) is because the precision was not extracted.

The rounding problem in mysql adapter has not been fixed, but `mysql_56`
helper tested only mysql2 adapter, its behavior was not apparent.

This reverts commit 1502caef.

The test suite for the mysql adapter broke when this commit was used
with MySQL 5.6.

Conflicts:
	activerecord/CHANGELOG.md

We do this in the adapter classes specifically, so the types aren't
registered if we don't use that adapter. Constants under the PostgreSQL
namespace for example are never loaded if we're using mysql.

The latest version of the PG gem can actually convert the primitives for
us in C code, which gives a pretty substantial speed up. A few cases
were only there to add the `infinity` method, which I just put on the
range type (which is the only place it was used). Floats also needed to
parse `Infinity` and `NaN`, but it felt reasonable enough to put that on
the generic form.

This predicate was only to figure out if it's safe to do case
insensitive comparison, which is only a problem on PG. Turns out, PG can
just tell us whether we are able to do it or not. If the query turns out
to be a problem, let's just replace that method with checking the SQL
type for `text` or `character`. I'd rather not burden the type objects
with adapter specific knowledge.

The *real* solution, is to deprecate this behavior entirely. The only
reason we need it is because the `:case_sensitive` option for
`validates_uniqueness_of` is documented as "this option is ignored for
non-strings". It makes no sense for us to do that. If the type can't be
compared in a case insensitive way, the user shouldn't tell us to do
case insensitive comparison.

The type from the column is never used, except when being passed to the
attributes API. While leaving the type on the column wasn't necessarily
a bad thing, I worry that it's existence there implies that it is
something which should be used.

During the design and implementation process of the attributes API,
there have been plenty of cases where getting the "right" type object
was hard, but I had easy access to the column objects. For any
contributor who isn't intimately familiar with the intents behind the
type casting system, grabbing the type from the column might easily seem
like the "correct" thing to do.

As such, the goal of this change is to express that the column is not
something that should be used for type casting. The only places that are
"valid" (at the time of this commit) uses of acquiring a type object
from the column are fixtures (as the YAML file is going to mirror the
database more closely than the AR object), and looking up the type
during schema detection to pass to the attributes API

Many of the failing tests were removed, as they've been made obsolete
over the last year. All of the PG column tests were testing nothing
beyond polymorphism. The Mysql2 tests were duplicating the mysql tests,
since they now share a column class.

The implementation is a little hairy, and slightly verbose, but it felt
preferable to going back to 20 constructor options for the columns. If
you are git blaming to figure out wtf I was thinking with them, and have
a better idea, go for it. Just don't use a type object for this.

`bound_attributes` is now used universally across the board, removing
the need for the conversion layer. These changes are mostly mechanical,
with the exception of the log subscriber. Additional, we had to
implement `hash` on the attribute objects, so they could be used as a
key for query caching.

Slightly refactoring `PostgreSQLColumn`. `array` should be readonly.
`default_function` should be initialized by `super`. `sql_type` has been
removed `[]`. Since we already choose to remove it we should not change.

In most cases, `create_table_definition` called by table_name (the first
argument) only.

If it is not a default primary key, correctly dump the type and options.

PG doesn't register it's types using the `int(4)` format that others do.
As such, if we alias `int8` to the other integer types, the range
information is lost. This is fixed by simply registering it separately.

The other option (which I specifically chose to avoid) is to pass the
information of the original type that was being aliased as an argument.
I'd rather avoid that, since an alias should truly be treated the same.
If we need different behavior for a different type, we should explicitly
register it with that, and not have a conditional based on aliasing.

Fixes #18144

[Sean Griffin & ysbaddaden]

The type registration was simply looking for the OID, and eagerly
fetching/constructing the sub type when it was registered. However,
numeric types have additional parameters which are extracted from the
actual SQL string of the type during lookup, and can have their behavior
change based on the result.

We simply need to use the block form of registration, and look up the
subtype lazily instead.

Fixes #17935

Fixes: https://github.com/rails/rails/issues/17856.

I grepped the source code for code snippets wrapped in backticks in the comments
and replaced the backticks with plus signs so they are correctly displayed in
the Rails documentation.

[ci skip]

This reverts commit da99a2a2.

also increase the version of pg required so that people will get the
GVL friendly version

MySQL reports the column name as `"MAX(developer_id)"`. PG will report
it as `"max"`

The `select` method has the same definition in almost all database
adapters, so it can be moved from the database-specific adapters
(PostgreSQl, MySQL, SQLite) to the abstract `database_statement`:

```ruby
def select(sql, name = nil, binds = [])
  exec_query(sql, name, binds)
end
```

---

More details about this commit: the only two DB-specific adapters
that have a different definition of `select` are MySQLAdapter and
MySQL2Adapter.

In MySQLAdapter, `select` invokes `exec_query(sql, name, binds)`, so
calling `super` achieves the same goal with less repetition.

In MySQL2Adapter, `select` invokes `exec_query(sql, name)`, that is,
it does not pass the `binds` parameter like other methods do. However,
[MySQL2Adapter's `exec_query`](https://github.com/rails/rails/blob/74a527cc63ef56f3d0a42cf638299958dc7cb08c/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb#L228L231)
works exactly the same whether this parameters is passed or not, so the output
does not change:

```ruby
def exec_query(sql, name = 'SQL', binds = [])
  result = execute(sql, name)
  ActiveRecord::Result.new(result.fields, result.to_a)
end
```

In the DSL you can now do:

create_table(:foos) do |t|
  t.bigint :hi
end

it doesn't work on SQLite3 since it doesn't support truncate, but that's
OK.  If you call truncate on the connection, you're now bound to that
database (same as if you use hstore or any other db specific feature).

`AbstractAdapter#supports_views?` defaults to `false` so we have to turn it on
in adapter subclasses. Currently the flag only controls test execution.

/cc @yahonda

[Philippe Creux, Chris Teague]

Fix CVE-2014-3483 and protect against CVE-2014-3482.

The only case where we got a column that was not `nil`, but did not
respond to `cast_type` was when type casting the default value during
schema creation. We can look up the cast type, and add that object to
the column definition. Will allow us to consistently rely on the type
objects for type casting in all directions.