2.0.0rc2

Released: January 9, 2023

orm

• [orm] [bug] Fixed issue where an overly restrictive ORM mapping rule were added in 2.0
  which prevented mappings against TableClause objects, such as
  those used in the view recipe on the wiki.

  References: #9071

typing

• [typing] [bug] The Data Class Transforms argument field_descriptors was renamed
  to field_specifiers in the accepted version of PEP 681.

  References: #9067

postgresql

• [postgresql] [bug] Added support to the asyncpg dialect to return the cursor.rowcount
  value for SELECT statements when available. While this is not a typical use
  for cursor.rowcount, the other PostgreSQL dialects generally provide
  this value. Pull request courtesy Michael Gorven.

  This change is also backported to: 1.4.47

  References: #9048

• [postgresql] [json] Implemented missing JSONB operations:

  -   `@@` using `_postgresql.JSONB.Comparator.path_match()`
  
  -   `@?` using `_postgresql.JSONB.Comparator.path_exists()`
  
  -   `#-` using `_postgresql.JSONB.Comparator.delete_path()`
  

  Pull request curtesy of Guilherme Martins Crocetti.

  References: #7147

mysql

• [mysql] [usecase] Added support to MySQL index reflection to correctly reflect the
  mysql_length dictionary, which previously was being ignored.

  This change is also backported to: 1.4.47

  References: #9047

• [mysql] [bug] Restored the behavior of 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 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
  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 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.

  References: #9058

oracle

• [oracle] [bug] Supported use case for foreign key constraints where the local column is
  marked as "invisible". The errors normally generated when a
  ForeignKeyConstraint is created that check for the target column
  are disabled when reflecting, and the constraint is skipped with a warning
  in the same way which already occurs for an Index with a similar
  issue.

  References: #9059