:released: January 22, 2020

 .. change::
     :tags: bug, postgresql
     :tickets: 5039

     Fixed issue where the PostgreSQL dialect would fail to parse a reflected
     CHECK constraint that was a boolean-valued function (as opposed to a
     boolean-valued expression).

 .. change::
     :tags: bug, ext
     :tickets: 5086

     Fixed bug in sqlalchemy.ext.serializer where a unique
     :class:`.BindParameter` object could conflict with itself if it were
     present in the mapping itself, as well as the filter condition of the
     query, as one side would be used against the non-deserialized version and
     the other side would use the deserialized version.  Logic is added to
     :class:`.BindParameter` similar to its "clone" method which will uniquify
     the parameter name upon deserialize so that it doesn't conflict with its
     original.


 .. change::
     :tags: usecase, sql
     :tickets: 5079

     A function created using :class:`.GenericFunction` can now specify that the
     name of the function should be rendered with or without quotes by assigning
     the :class:`.quoted_name` construct to the .name element of the object.
     Prior to 1.3.4, quoting was never applied to function names, and some
     quoting was introduced in :ticket:`4467` but no means to force quoting for
     a mixed case name was available.  Additionally, the :class:`.quoted_name`
     construct when used as the name will properly register its lowercase name
     in the function registry so that the name continues to be available via the
     ``func.`` registry.

     .. seealso::

         :class:`.GenericFunction`


 .. change::
     :tags: bug, engine
     :tickets: 5048

     Fixed issue where the collection of value processors on a
     :class:`.Compiled` object would be mutated when "expanding IN" parameters
     were used with a datatype that has bind value processors; in particular,
     this would mean that when using statement caching and/or baked queries, the
     same compiled._bind_processors collection would be mutated concurrently.
     Since these processors are the same function for a given bind parameter
     namespace every time, there was no actual negative effect of this issue,
     however, the execution of a :class:`.Compiled` object should never be
     causing any changes in its state, especially given that they are intended
     to be thread-safe and reusable once fully constructed.


 .. change::
     :tags: tests, postgresql
     :tickets: 5057

     Improved detection of two phase transactions requirement for the PostgreSQL
     database by testing that max_prepared_transactions is set to a value
     greater than 0.  Pull request courtesy Federico Caselli.


 .. change::
     :tags: bug, orm, engine
     :tickets: 5056, 5050, 5071

     Added test support and repaired a wide variety of unnecessary reference
     cycles created for short-lived objects, mostly in the area of ORM queries.
     Thanks much to Carson Ip for the help on this.


 .. change::
     :tags: orm, bug
     :tickets: 5107

     Fixed regression in loader options introduced in 1.3.0b3 via :ticket:`4468`
     where the ability to create a loader option using
     :meth:`.PropComparator.of_type` targeting an aliased entity that is an
     inheriting subclass of the entity which the preceding relationship refers
     to would fail to produce a matching path.   See also :ticket:`5082` fixed
     in this same release which involves a similar kind of issue.

 .. change::
     :tags: bug, tests
     :tickets: 4946

     Fixed a few test failures which would occur on Windows due to SQLite file
     locking issues, as well as some timing issues in connection pool related
     tests; pull request courtesy Federico Caselli.


 .. change::
     :tags: orm, bug
     :tickets: 5082

     Fixed regression in joined eager loading introduced in 1.3.0b3 via
     :ticket:`4468` where the ability to create a joined option across a
     :func:`.with_polymorphic` into a polymorphic subclass using
     :meth:`.RelationshipProperty.of_type` and then further along regular mapped
     relationships would fail as the polymorphic subclass would not add itself
     to the load path in a way that could be located by the loader strategy.  A
     tweak has been made to resolve this scenario.


 .. change::
     :tags: performance, orm

     Identified a performance issue in the system by which a join is constructed
     based on a mapped relationship.   The clause adaption system would be used
     for the majority of join expressions including in the common case where no
     adaptation is needed.   The conditions under which this adaptation occur
     have been refined so that average non-aliased joins along a simple
     relationship without a "secondary" table use about 70% less function calls.


 .. change::
     :tags: usecase, postgresql
     :tickets: 5040

     Added support for prefixes to the :class:`.CTE` construct, to allow
     support for Postgresql 12 "MATERIALIZED" and "NOT MATERIALIZED" phrases.
     Pull request courtesy Marat Sharafutdinov.

     .. seealso::

         :meth:`.HasCTE.cte`

 .. change::
     :tags: bug, mssql
     :tickets: 5045

     Fixed issue where a timezone-aware ``datetime`` value being converted to
     string for use as a parameter value of a :class:`.mssql.DATETIMEOFFSET`
     column was omitting the fractional seconds.

 .. change::
     :tags: bug, orm
     :tickets: 5068

     Repaired a warning in the ORM flush process that was not covered by  test
     coverage when deleting objects that use the "version_id" feature. This
     warning is generally unreachable unless using a dialect that sets the
     "supports_sane_rowcount" flag to False, which  is not typically the case
     however is possible for some MySQL configurations as well as older Firebird
     drivers, and likely some third party dialects.

 .. change::
     :tags: bug, orm
     :tickets: 5065

     Fixed bug where usage of joined eager loading would not properly wrap the
     query inside of a subquery when :meth:`.Query.group_by` were used against
     the query.   When any kind of result-limiting approach is used, such as
     DISTINCT, LIMIT, OFFSET, joined eager loading embeds the row-limited query
     inside of a subquery so that the collection results are not impacted.   For
     some reason, the presence of GROUP BY was never included in this criterion,
     even though it has a similar effect as using DISTINCT.   Additionally, the
     bug would prevent using GROUP BY at all for a joined eager load query for
     most database platforms which forbid non-aggregated, non-grouped columns
     from being in the query, as the additional columns for the joined eager
     load would not be accepted by the database.



.. changelog::