The support for pool ping listeners to receive exception events via the
:meth:`.ConnectionEvents.handle_error` event added in 2.0.0b1 for
:ticket:`5648` failed to take into account dialect-specific ping routines
such as that of MySQL and PostgreSQL. The dialect feature has been reworked
so that all dialects participate within event handling.   Additionally,
a new boolean element :attr:`.ExceptionContext.is_pre_ping` is added
which identifies if this operation is occurring within the pre-ping
operation.

For this release, third party dialects which implement a custom
:meth:`_engine.Dialect.do_ping` method can opt in to the newly improved
behavior by having their method no longer catch exceptions or check
exceptions for "is_disconnect", instead just propagating all exceptions
outwards. Checking the exception for "is_disconnect" is now done by an
enclosing method on the default dialect, which ensures that the event hook
is invoked for all exception scenarios before testing the exception as a
"disconnect" exception. If an existing ``do_ping()`` method continues to
catch exceptions and check "is_disconnect", it will continue to work as it
did previously, but ``handle_error`` hooks will not have access to the
exception if it isn't propagated outwards.

Fixes: #5648
Change-Id: I6535d5cb389e1a761aad8c37cfeb332c548b876d

Remove ``typing.Self`` workaround, now using :pep:`673` for most methods
that return ``Self``. Pull request courtesy Yurii Karabas.

Fixes: #9254
Closes: #9255
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/9255
Pull-request-sha: 2947df8ada79f5c3afe9c838e65993302199c2f7

Change-Id: Ic32015ad52e95a61f3913d43ea436aa9402804df

Fixed regression caused by issue :ticket:`9058` which adjusted the MySQL
dialect's ``has_table()`` to again use "DESCRIBE", where the specific error
code raised by MySQL version 8 when using a non-existent schema name was
unexpected and failed to be interpreted as a boolean result.

Fixed the SQLite dialect's ``has_table()`` function to correctly report
False for queries that include a non-None schema name for a schema that
doesn't exist; previously, a database error was raised.

Fixes: #9251
Change-Id: I5ef9cf0887865c3c521d88bca0ba18954a108241

Added support for MySQL 8's new ``AS <name> ON DUPLICATE KEY`` syntax when
using :meth:`_mysql.Insert.on_duplicate_key_update`, which is required for
newer versions of MySQL 8 as the previous syntax using ``VALUES()`` now
emits a deprecation warning with those versions. Server version detection
is employed to determine if traditional MariaDB / MySQL < 8 ``VALUES()``
syntax should be used, vs. the newer MySQL 8 required syntax. Pull request
courtesy Caspar Wylie.

Fixes: #8626
Closes: #9210
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/9210
Pull-request-sha: 1c8dfbf0b4c439d9ca2c194524c47eb7239ee3c5

Change-Id: I42c463837af06bc15b60c534159804193df07f02

Fixes: #9084
Change-Id: I5e174c318a20b7fcb5ea7c771293c5102e761ed7

change {opensql} to {printsql} in prints, add missing markers

Change-Id: I07b72e6620bb64e329d6b641afa27631e91c4f16

Restored the behavior of :meth:`.Inspector.has_table` to report on
temporary tables for MySQL / MariaDB. This is currently the behavior for
all other included dialects, but was removed for MySQL in 1.4 due to no
longer using the DESCRIBE command; there was no documented support for temp
tables being reported by the :meth:`.Inspector.has_table` method in this
version or on any previous version, so the previous behavior was undefined.

As SQLAlchemy 2.0 has added formal support for temp table status via
:meth:`.Inspector.has_table`, the MySQL /MariaDB dialect has been reverted
to use the "DESCRIBE" statement as it did in the SQLAlchemy 1.3 series and
previously, and test support is added to include MySQL / MariaDB for
this behavior.   The previous issues with ROLLBACK being emitted which
1.4 sought to improve upon don't apply in SQLAlchemy 2.0 due to
simplifications in how :class:`.Connection` handles transactions.

DESCRIBE is necessary as MariaDB in particular has no consistently
available public information schema of any kind in order to report on temp
tables other than DESCRIBE/SHOW COLUMNS, which rely on throwing an error
in order to report no results.

Fixes: #9058
Change-Id: Ic511bd5989ec17beb37b7cddd913732b626af0e6