1.2.8

Released: May 28, 2018

• [bug] [orm] Fixed regression in 1.2.7 caused by #4228, which itself was fixing
  a 1.2-level regression, where the query_cls callable passed to a
  Session was assumed to be a subclass of Query with
  class method availability, as opposed to an arbitrary callable. In
  particular, the dogpile caching example illustrates query_cls as a
  function and not a Query subclass.

  References: #4256

• [bug] [engine] Fixed connection pool issue whereby if a disconnection error were raised
  during the connection pool's "reset on return" sequence in conjunction with
  an explicit transaction opened against the enclosing Connection
  object (such as from calling Session.close() without a rollback or
  commit, or calling Connection.close() without first closing a
  transaction declared with Connection.begin()), a double-checkin would
  result, which could then lead towards concurrent checkouts of the same
  connection. The double-checkin condition is now prevented overall by an
  assertion, as well as the specific double-checkin scenario has been
  fixed.

  References: #4252

• [bug] [oracle] The Oracle BINARY_FLOAT and BINARY_DOUBLE datatypes now participate within
  cx_Oracle.setinputsizes(), passing along NATIVE_FLOAT, so as to support the
  NaN value. Additionally, oracle.BINARY_FLOAT,
  oracle.BINARY_DOUBLE and oracle.DOUBLE_PRECISION now
  subclass Float, since these are floating point datatypes, not
  decimal. These datatypes were already defaulting the
  Float.asdecimal flag to False in line with what
  Float already does.

  References: #4264

• [bug] [oracle] Added reflection capabilities for the oracle.BINARY_FLOAT,
  oracle.BINARY_DOUBLE datatypes.

• [bug] [ext] The horizontal sharding extension now makes use of the identity token
  added to ORM identity keys as part of #4137, when an object
  refresh or column-based deferred load or unexpiration operation occurs.
  Since we know the "shard" that the object originated from, we make
  use of this value when refreshing, thereby avoiding queries against
  other shards that don't match this object's identity in any case.

  References: #4247

• [bug] [sql] Fixed issue where the "ambiguous literal" error message used when
  interpreting literal values as SQL expression values would encounter a
  tuple value, and fail to format the message properly. Pull request courtesy
  Miguel Ventura.

• [bug] [mssql] Fixed a 1.2 regression caused by #4061 where the SQL Server
  "BIT" type would be considered to be "native boolean". The goal here
  was to avoid creating a CHECK constraint on the column, however the bigger
  issue is that the BIT value does not behave like a true/false constant
  and cannot be interpreted as a standalone expression, e.g.
  "WHERE ". The SQL Server dialect now goes back to being
  non-native boolean, but with an extra flag that still avoids creating
  the CHECK constraint.

  References: #4250

• [bug] [oracle] Altered the Oracle dialect such that when an Integer type is in
  use, the cx_Oracle.NUMERIC type is set up for setinputsizes(). In
  SQLAlchemy 1.1 and earlier, cx_Oracle.NUMERIC was passed for all numeric
  types unconditionally, and in 1.2 this was removed to allow for better
  numeric precision. However, for integers, some database/client setups
  will fail to coerce boolean values True/False into integers which introduces
  regressive behavior when using SQLAlchemy 1.2. Overall, the setinputsizes
  logic seems like it will need a lot more flexibility going forward so this
  is a start for that.

  References: #4259

• [bug] [engine] Fixed a reference leak issue where the values of the parameter dictionary
  used in a statement execution would remain referenced by the "compiled
  cache", as a result of storing the key view used by Python 3 dictionary
  keys(). Pull request courtesy Olivier Grisel.

• [bug] [orm] Fixed a long-standing regression that occurred in version
  1.0, which prevented the use of a custom MapperOption
  that alters the _params of a Query object for a
  lazy load, since the lazy loader itself would overwrite those
  parameters. This applies to the "temporal range" example
  on the wiki. Note however that the
  Query.populate_existing() method is now required in
  order to rewrite the mapper options associated with an object
  already loaded in the identity map.

  As part of this change, a custom defined
  MapperOption will now cause lazy loaders related to
  the target object to use a non-baked query by default unless
  the MapperOption._generate_cache_key() method is implemented.
  In particular, this repairs one regression which occurred when
  using the dogpile.cache "advanced" example, which was not
  returning cached results and instead emitting SQL due to an
  incompatibility with the baked query loader; with the change,
  the RelationshipCache option included for many releases
  in the dogpile example will disable the "baked" query altogether.
  Note that the dogpile example is also modernized to avoid both
  of these issues as part of issue #4258.

  References: #4128

• [bug] [ext] Fixed a race condition which could occur if automap
  AutomapBase.prepare() were used within a multi-threaded context
  against other threads which may call configure_mappers() as a
  result of use of other mappers. The unfinished mapping work of automap
  is particularly sensitive to being pulled in by a
  configure_mappers() step leading to errors.

  References: #4266

• [bug] [orm] Fixed bug where the new baked.Result.with_post_criteria()
  method would not interact with a subquery-eager loader correctly,
  in that the "post criteria" would not be applied to embedded
  subquery eager loaders. This is related to #4128 in that
  the post criteria feature is now used by the lazy loader.

• [bug] [tests] Fixed a bug in the test suite where if an external dialect returned
  None for server_version_info, the exclusion logic would raise an
  AttributeError.

  References: #4249

• [bug] [orm] Updated the dogpile.caching example to include new structures that
  accommodate for the "baked" query system, which is used by default within
  lazy loaders and some eager relationship loaders. The dogpile.caching
  "relationship_caching" and "advanced" examples were also broken due to
  #4256. The issue here is also worked-around by the fix in
  #4128.

  References: #4258