1.3.7

Released: August 14, 2019

• [bug] [sql] Fixed issue where Index object which contained a mixture of
  functional expressions which were not resolvable to a particular column,
  in combination with string-based column names, would fail to initialize
  its internal state correctly leading to failures during DDL compilation.

  References: #4778

• [bug] [sqlite] The dialects that support json are supposed to take arguments
  json_serializer and json_deserializer at the create_engine() level,
  however the SQLite dialect calls them _json_serilizer and
  _json_deserilalizer. The names have been corrected, the old names are
  accepted with a change warning, and these parameters are now documented as
  create_engine.json_serializer and
  create_engine.json_deserializer.

  References: #4798

• [bug] [mysql] The MySQL dialects will emit "SET NAMES" at the start of a connection when
  charset is given to the MySQL driver, to appease an apparent behavior
  observed in MySQL 8.0 that raises a collation error when a UNION includes
  string columns unioned against columns of the form CAST(NULL AS CHAR(..)),
  which is what SQLAlchemy's polymorphic_union function does. The issue
  seems to have affected PyMySQL for at least a year, however has recently
  appeared as of mysqlclient 1.4.4 based on changes in how this DBAPI creates
  a connection. As the presence of this directive impacts three separate
  MySQL charset settings which each have intricate effects based on their
  presense, SQLAlchemy will now emit the directive on new connections to
  ensure correct behavior.

  References: #4804

• [postgresql] [usecase] Added new dialect flag for the psycopg2 dialect, executemany_mode which
  supersedes the previous experimental use_batch_mode flag.
  executemany_mode supports both the "execute batch" and "execute values"
  functions provided by psycopg2, the latter which is used for compiled
  insert() constructs. Pull request courtesy Yuval Dinari.

  References: #4623

• [bug] [sql] Fixed bug where TypeEngine.column_expression() method would not be
  applied to subsequent SELECT statements inside of a UNION or other
  CompoundSelect, even though the SELECT statements are rendered at
  the topmost level of the statement. New logic now differentiates between
  rendering the column expression, which is needed for all SELECTs in the
  list, vs. gathering the returned data type for the result row, which is
  needed only for the first SELECT.

  References: #4787

• [bug] [sqlite] Fixed bug where usage of "PRAGMA table_info" in SQLite dialect meant that
  reflection features to detect for table existence, list of table columns,
  and list of foreign keys, would default to any table in any attached
  database, when no schema name was given and the table did not exist in the
  base schema. The fix explicitly runs PRAGMA for the 'main' schema and then
  the 'temp' schema if the 'main' returned no rows, to maintain the behavior
  of tables + temp tables in the "no schema" namespace, attached tables only
  in the "schema" namespace.

  References: #4793

• [bug] [sql] Fixed issue where internal cloning of SELECT constructs could lead to a key
  error if the copy of the SELECT changed its state such that its list of
  columns changed. This was observed to be occurring in some ORM scenarios
  which may be unique to 1.3 and above, so is partially a regression fix.

  References: #4780

• [bug] [orm] Fixed regression caused by new selectinload for many-to-one logic where
  a primaryjoin condition not based on real foreign keys would cause
  KeyError if a related object did not exist for a given key value on the
  parent object.

  References: #4777

• [mysql] [usecase] Added reserved words ARRAY and MEMBER to the MySQL reserved words list, as
  MySQL 8.0 has now made these reserved.

  References: #4783

• [bug] [events] Fixed issue in event system where using the once=True flag with
  dynamically generated listener functions would cause event registration of
  future events to fail if those listener functions were garbage collected
  after they were used, due to an assumption that a listened function is
  strongly referenced. The "once" wrapped is now modified to strongly
  reference the inner function persistently, and documentation is updated
  that using "once" does not imply automatic de-registration of listener
  functions.

  References: #4794

• [bug] [mysql] Added another fix for an upstream MySQL 8 issue where a case sensitive
  table name is reported incorrectly in foreign key constraint reflection,
  this is an extension of the fix first added for #4344 which
  affects a case sensitive column name. The new issue occurs through MySQL
  8.0.17, so the general logic of the 88718 fix remains in place.

  References: #4751

• [mssql] [usecase] Added new mssql.try_cast() construct for SQL Server which emits
  "TRY_CAST" syntax. Pull request courtesy Leonel Atencio.

  References: #4782

• [bug] [orm] Fixed bug where using Query.first() or a slice expression in
  conjunction with a query that has an expression based "offset" applied
  would raise TypeError, due to an "or" conditional against "offset" that did
  not expect it to be a SQL expression as opposed to an integer or None.

  References: #4803