with :meth:`.Connection.execution_options` when a :class:`.Transaction` is in play; DBAPIs and/or SQLAlchemy dialects such as psycopg2, MySQLdb may implicitly rollback or commit the transaction, or not change the setting til next transaction, so this is never safe. - Added new parameter :paramref:`.Session.connection.execution_options` which may be used to set up execution options on a :class:`.Connection` when it is first checked out, before the transaction has begun. This is used to set up options such as isolation level on the connection before the transaction starts. - added new documentation section detailing best practices for setting transaction isolation with sessions. fixes #3296
logic to some degree in DefaultExecutionContext. In particular we are removing post_insert() which doesn't appear to be used based on a survey of prominent third party dialects. Callcounts aren't added to existing execute profiling tests and inserts might be a little better. - simplify the execution_options join in DEC. Callcounts don't appear affected.
repaired to work more usefully with tables that have Python- side default values and/or functions, as well as server-side defaults. The feature will now work with a dialect that uses "positional" parameters; a Python callable will also be invoked individually for each row just as is the case with an "executemany" style invocation; a server- side default column will no longer implicitly receive the value explicitly specified for the first row, instead refusing to invoke without an explicit value. fixes #3288
to get all flake8 passing
it for DELETE would fail to target the correct row for DELETE. Then to compound matters, basic "number of rows matched" checks were not being performed. Both issues are fixed, however note that the "rows matched" check requires so-called "sane multi-row count" functionality; the DBAPI's executemany() method must count up the rows matched by individual statements and SQLAlchemy's dialect must mark this feature as supported, currently applies to some mysql dialects, psycopg2, sqlite only. fixes #3006 - Enabled "sane multi-row count" checking for the psycopg2 DBAPI, as this seems to be supported as of psycopg2 2.0.9.
MySQL, to correctly render the SET clause among multiple columns with the same name across tables. This also changes the name used for the bound parameter in the SET clause to "<tablename>_<colname>" for the non-primary table only; as this parameter is typically specified using the :class:`.Column` object directly this should not have an impact on applications. The fix takes effect for both :meth:`.Table.update` as well as :meth:`.Query.update` in the ORM. [ticket:2912]