Use “distinct” to filter redundant types from pg_typeto reduce memory bloat especially in multi-schema structure database

Actually `index_name_length` depend on `max_identifier_length`, not
always 63.

`supports_migrations?` was added at 4160b518 to determine if schema
statements (`create_table`, `drop_table`, etc) are implemented in the
adapter. But all tested databases has been supported migrations since
a4fc93c3 at least.

`valid_type?` should return true if a type exists in
`native_database_types` at least.

https://github.com/rails/rails/blob/v5.1.0.beta1/activerecord/lib/active_record/schema_dumper.rb#L136

This ensures multiple threads inside a transactional test to see consistent
database state.

When a system test starts Puma spins up one thread and Capybara spins up
another thread. Because of this when tests are run the database cannot
see what was inserted into the database on teardown. This is because
there are two threads using two different connections.

This change uses the statement cache to lock the threads to using a
single connection ID instead of each not being able to see each other.
This code only runs in the fixture setup and teardown so it does not
affect real production databases.

When a transaction is opened we set `lock_thread` to `Thread.current` so
we can keep track of which connection the thread is using. When we
rollback the transaction we unlock the thread and then there will be no
left-over data in the database because the transaction will roll back
the correct connections.

[ Eileen M. Uchitelle, Matthew Draper ]

Add `default_index_type?` to the generic schema dumper doesn't have the knowledge about an index type

Closes #27980

Closes #27979

`supports_primary_key?` was added to determine if `primary_key` is
implemented in the adapter in f0602214. But we already use `primary_key`
without `supports_primary_key?` (207f266c, 5f3cf424) and using
`supports_primary_key?` has been removed in #1318. This means that
`supports_primary_key?` is no longer used in the internal and Active
Record doesn't work without `primary_key` is implemented (all adapters
must implement `primary_key`).

Closes #27977

Column options are passed as an hash args then used as `options` hash in
`add_column_options!`. Converting args to attributes is inconvinient for
using options as an hash.

column_definitions() needs to fetch the collation for every column, if
present. Previously, it did so using a correlated subquery - a subquery
that references results from the outer scope.

This patch updates the query to remove the subquery in favor of a
simpler and more efficient JOIN clause.

Running the two queries through EXPLAIN against Postgres additionally
shows that the original form with a correlated subquery requires a
Nested Loop Left Join, while the new form with a simple JOIN can use a
more efficient Merge Left Join.

One empty string allocation per column per row.

Revert "Merge pull request #21233 from mtsmfm/disable-referential-integrity-without-superuser-privileges"

This reverts commit eeac6151, reversing
changes made to 5c40239d.

Reason: Broke the isolated tests.
https://travis-ci.org/rails/rails/builds/188721346

Some methods were added to public API in
5b14129d and they should be not part of
the public API.

Raise `ActiveRecord::RangeError` when values that executed are out of range.

Raise `ActiveRecord::NotNullViolation` when a record cannot be inserted
or updated because it would violate a not null constraint.

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>