"Implicit autocommit", which is the COMMIT that occurs when a DML or DDL
statement is emitted on a connection, is deprecated and won't be part of
SQLAlchemy 2.0.   A 2.0-style warning is emitted when autocommit takes
effect, so that the calling code may be adjusted to use an explicit
transaction.

As part of this change, DDL methods such as
:meth:`_schema.MetaData.create_all` when used against a
:class:`_engine.Engine` or :class:`_engine.Connection` will run the
operation in a BEGIN block if one is not started already.

The MySQL and MariaDB dialects now query from the information_schema.tables
system view in order to determine if a particular table exists or not.
Previously, the "DESCRIBE" command was used with an exception catch to
detect non-existent,  which would have the undesirable effect of emitting a
ROLLBACK on the connection. There appeared to be legacy encoding issues
which prevented the use of "SHOW TABLES", for this, but as MySQL support is
now at 5.0.2  or above due to :ticket:`4189`, the information_schema tables
are now available in all cases.

Fixes: #4846
Change-Id: I733a7e0e17477a63607fb9931c87c393bbd7ac57

MySQL dialect's server_version_info tuple is now all numeric.  String
tokens like "MariaDB" are no longer present so that numeric comparison
works in all cases.  The .is_mariadb flag on the dialect should be
consulted for whether or not mariadb was detected.   Additionally removed
structures meant to support extremely old MySQL versions 3.x and 4.x;
the minimum MySQL version supported is now version 5.0.2.

In addition, as the "MariaDB" name goes away from server version,
expand upon the change in I330815ebe572b6a9818377da56621397335fa702
to support the name "mariadb" throughout the dialect and test suite
when mariadb-only mode is used.    This changes the "name" field
on the MariaDB dialect to "mariadb", which then implies a change
throughout the testing requirements system as well as all the
dialect-specific DDL argument names such as "mysql_engine" is
now specified as "mariadb_engine", etc.   Make use of the
recent additions to test suite URL provisioning so that we can
force MariaDB databases to have a "mariadb-only" dialect which
allows us to test this name change fully.

Update documentation to refer to MySQL / MariaDB explicitly
as well as indicating the "mariadb_" prefix used for options.

It seems likely that MySQL and MariaDB version numbers are going to
start colliding at some point so having the "mariadb" name
be available as a totally separate dialect name should give us
some options in this regard.

Currently also includes a date related fix to a test for
the postgresql dialect that was implicitly assuming a
non-UTC timezone

Fixes: #4189
Change-Id: I00e76d00f62971e1f067bd61915fa6cc1cf64e5e

Change-Id: I08440dc25e40ea1ccea1778f6ee9e28a00808235

This affects mostly docstrings, except in orm/events.py::dispose_collection()
where one parameter gets renamed: given that the method is
empty, it seemed reasonable to me to fix that too.

Closes: #4440
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4440
Pull-request-sha: 779ed75acb6142e1f1daac467b5b14134529bb4b

Change-Id: Ic0553fe97853054b09c2453af76d96363de6eb0e

Change-Id: I6a71f4924d046cf306961c58dffccf21e9c03911

Applied on top of a pure run of black -l 79 in
I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9,  this set of changes
resolves all remaining flake8 conditions for those codes
we have enabled in setup.cfg.

Included are resolutions for all remaining flake8 issues
including shadowed builtins, long lines, import order, unused
imports, duplicate imports, and docstring issues.

Change-Id: I4f72d3ba1380dd601610ff80b8fb06a2aff8b0fe

This is a straight reformat run using black as is, with no edits
applied at all.

The black run will format code consistently, however in
some cases that are prevalent in SQLAlchemy code it produces
too-long lines.   The too-long lines will be resolved in the
following commit that will resolve all remaining flake8 issues
including shadowed builtins, long lines, import order, unused
imports, duplicate imports, and docstring issues.

Change-Id: I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9

Fixed bug in MySQLdb dialect and variants such as PyMySQL where an
additional "unicode returns" check upon connection makes explicit use of
the "utf8" character set, which in MySQL 8.0 emits a warning that utf8mb4
should be used.  This is now replaced with a utf8mb4 equivalent.
Documentation is also updated for the MySQL dialect to specify utf8mb4 in
all examples.  Additional changes have been made to the test suite to use
utf8mb3 charsets and databases (there seem to be collation issues in some
edge cases with utf8mb4), and to support configuration default changes made
in MySQL 8.0 such as explicit_defaults_for_timestamp as well as new errors
raised for invalid MyISAM indexes.

Change-Id: Ib596ea7de4f69f976872a33bffa4c902d17dea25
Fixes: #4283
Fixes: #4192

Change-Id: I3ef36bfd0cb0ba62b3123c8cf92370a43156cf8f

After bump minimum supported version to 2.7 (1da9d3752160430c91534a8868ceb8c5ad1451d4), we can use new syntax.

Change-Id: Ib064c75a00562e641d132f9c57e5e69744200e05
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/347