Fixed issue to workaround SQLite's behavior of assigning "numeric" affinity
to JSON datatypes, first described at :ref:`change_3850`, which returns
scalar numeric JSON values as a number and not as a string that can be JSON
deserialized.  The SQLite-specific JSON deserializer now gracefully
degrades for this case as an exception and bypasses deserialization for
single numeric values, as from a JSON perspective they are already
deserialized.

Also adds a combinatoric fixture for JSON single values within
the dialect-general test suite.

Fixes: #5014
Change-Id: Id38221dce1271fec527ca198b23908547b25d8a0

Some upcoming commits will make use of @metadata_fixture
within a TablesTest class.  As the fixture takes place before
setup, remove anything in setup that would interfere with it.

Change-Id: I4f16889c4c02cb2835dcf4886eb09ece848d8109
References: I507bc405eee6cae2c5991345d0eac53a37fe7512

Added support for use of the :class:`.Sequence` construct with MariaDB 10.3
and greater, as this is now supported by this database.  The construct
integrates with the :class:`.Table` object in the same way that it does for
other databases like PostrgreSQL and Oracle; if is present on the integer
primary key "autoincrement" column, it is used to generate defaults.   For
backwards compatibility, to support a :class:`.Table` that has a
:class:`.Sequence` on it to support sequence only databases like Oracle,
while still not having the sequence fire off for MariaDB, the optional=True
flag should be set, which indicates the sequence should only be used to
generate the primary key if the target database offers no other option.

Fixes: #4976
Closes: #4996
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4996
Pull-request-sha: cb2e1426ea0b6bc6c93dbe8f033a11df9d8c4915

Change-Id: I507bc405eee6cae2c5991345d0eac53a37fe7512

Previously, uses_objects was specific to the SynonymAttribute;
generalize it so that it defaults to False for other DescriptorProps.
Immediate fix is against CompositeProperty.

Fixed regression introduced in 1.3.0 related to the association proxy
refactor in :ticket:`4351` that prevented :func:`.composite` attributes
from working in terms of an association proxy that references them.

Add test coverage for association proxies that refer to Composite
attributes as endpoints.

Fixes: #5000
Change-Id: Iea6fb1bd3314d861a9bc22491b0ae1e6c5e6340d

A helper for @testing.combinations when we just have lots of
true/false combinations as is the case with some ORM tests.

Change-Id: I9f2de97ce5b2487411ed610b8d41169c1052bd8f

- ensure we escape out percent signs when a CompiledSQL or RegexSQL
has percent signs in the SQL or in the parameter repr

- to support combinations, print out complete test name in skip
messages, py.test environment gives us a way to do this

Change-Id: Ia9e62f7c1026c1465986144c5757e35fc164a2b8

Added new accessors to expressions of type :class:`.JSON` to allow for
specific datatype access and comparison, covering strings, integers,
numeric, boolean elements.   This revises the documented approach of
CASTing to string when comparing values, instead adding specific
functionality into the PostgreSQL, SQlite, MySQL dialects to reliably
deliver these basic types in all cases.

The change also delivers a new feature to the test exclusions
system so that combinations and exclusions can be used together.

Fixes: #4276
Change-Id: Ica5a926c060feb40a0a7cd60b9d6e061d7825728

Like py.test we need to be able to mark certain combination
elements with exclusion rules.   Add additional logic
to pytestlplugin and exclusions so that the exclusion decorators
can be added to the combination tuples, where they will be applied
to the decorated function along with a qualifier that the test
arguments need to match what's given.

Change-Id: I15d2839954d77a252bab5aaf6e3fd9f388c99dd5