Add support to ``FETCH {FIRST | NEXT} [ count ] {ROW | ROWS}
 {ONLY | WITH TIES}`` in the select for the supported backends,
currently PostgreSQL, Oracle and MSSQL.

Fixes: #5576
Change-Id: Ibb5871a457c0555f82b37e354e7787d15575f1f7

Added support for reflecting "identity" columns, which are now returned
as part of the structure returned by :meth:`_reflection.Inspector.get_columns`.
When reflecting full :class:`_schema.Table` objects, identity columns will
be represented using the :class:`_schema.Identity` construct.

Fixed compilation error on oracle for sequence and identity column
``nominvalue`` and ``nomaxvalue`` options that require no space in them.

Improved test compatibility with oracle 18.

As part of the support for reflecting :class:`_schema.Identity` objects,
the method :meth:`_reflection.Inspector.get_columns` no longer returns
``mssql_identity_start`` and ``mssql_identity_increment`` as part of the
``dialect_options``. Use the information in the ``identity`` key instead.

The mssql dialect will assume that at least MSSQL 2005 is used.
There is no hard exception raised if a previous version is detected,
but operations may fail for older versions.

Fixes: #5527
Fixes: #5324
Change-Id: If039fe637c46b424499e6bac54a2cbc0dc54cb57

It's better, the majority of these changes look more readable to me.
also found some docstrings that had formatting / quoting issues.

Change-Id: I582a45fde3a5648b2f36bab96bad56881321899b

Set default type codec for ``json`` and ``jsonb`` types when using
the asyncpg driver. By default asyncpg will not decode them and return
strings instead.

Fixes: #5584
Change-Id: I41348eff8096ccf87b952d7e797c0694c6c4b5c4

Provide support for multiple hosts in the PostgreSQL connection string.

A user requested for SQLAlchemy to support multiple hosts within a PostgreSQL URL string. The proposed fix allows this. In the event that the url contains multiple hosts the proposed code will convert the query["hosts"] tuple into a single string. This allows the hosts to then get converted into a valid dsn variable in the psycopg2 connect function.

This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [X ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**
Fixes: #4392

Closes: #5554
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5554
Pull-request-sha: 3f7a0ab8df9f1411a9f1ac0e152583bc7bf0c365

Change-Id: I3f3768d51b8331de786ffdc025b7ecfc662eafe5

Fixes: #5597

Fixes the issue where :meth:`_reflection.has_table` always returns
``False`` for temporary tables.

Change-Id: I03ab04c849a157ce8fd28c07ec3bf4407b0f2c94

For most from_self() tests, move them into
test/orm/test_deprecated.py and replace the existing
test with one that uses aliased() plus a subquery.
This then revealed a few more issues.

Related items:

* Added slice() method to GenerativeSelect, to match that
  of orm.Query and to make possible migration of one of the
  from_self() tests.  moved the utility functions used for this
  from orm/util into sql/util.

* repairs a caching issue related to subqueryload
  where information being derived from the cached path info
  was mixing up with query information based on the per-query
  state, specifically an AliasedClass that is per query.

* for the above issue, it seemed like path_registry maybe
  had to change so that it represents AliasedClass objects
  as their cache key rather than on identity, but it wasn't
  needed.  still seems like it would be more correct.

* enhances the error message raised by coercions for a case
  such as when an AliasedClass holds onto a select() object
  and not a subquery(); will name the original and resolved
  object for clarity  (although how is AliasedClass able to
  accept a Select() object in the first place?)

* Added _set_propagate_attrs() to Query so that again if
  it's passed to AliasedClass, it doesn't raise an error
  during coercion, but again maybe that should also be
  rejected up front

Fixes: #5368
Change-Id: I5912aa611d899acc87a75eb5ee9f95990592f210

Fixes: #5592
Change-Id: I0688e5ea0fc6b01a0b72f397daea8f57a2ec0766