diff options
| author | Mike Bayer <mike_mp@zzzcomputing.com> | 2013-10-23 20:07:48 -0400 |
|---|---|---|
| committer | Mike Bayer <mike_mp@zzzcomputing.com> | 2013-10-23 20:07:48 -0400 |
| commit | f0678a6e54e9598b884b82f43e57f44661693cca (patch) | |
| tree | c0dc390a15a69f919c172bb19d72f1282b8185f2 | |
| parent | 618f90df8e24ff0a326ed893d93e8103a0d8f58c (diff) | |
| download | sqlalchemy-f0678a6e54e9598b884b82f43e57f44661693cca.tar.gz | |
clarifications
| -rw-r--r-- | doc/build/changelog/migration_09.rst | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/doc/build/changelog/migration_09.rst b/doc/build/changelog/migration_09.rst index 570aa5cc7..4bc929f58 100644 --- a/doc/build/changelog/migration_09.rst +++ b/doc/build/changelog/migration_09.rst @@ -708,17 +708,17 @@ to the ``version_id_generator`` parameter, the ORM will use the already-set vers identifier, or alternatively fetch the version identifier from each row at the same time the INSERT or UPDATE is emitted. When using a server-generated version identifier, it is strongly -recommended that this feature be used only on a backend where RETURNING can also -be used, else the additional SELECT statements will add significant performance +recommended that this feature be used only on a backend with strong RETURNING +support (Postgresql, SQL Server; Oracle also supports RETURNING but the cx_oracle +driver has only limited support), else the additional SELECT statements will +add significant performance overhead. The example provided at :ref:`server_side_version_counter` illustrates the usage of the Postgresql ``xmin`` system column in order to integrate it with the ORM's versioning feature. -As a related feature, a new method :meth:`.ValuesBase.return_defaults` has been -added to :class:`.Insert` and :class:`.Update` which in constrast to the -:meth:`.UpdateBase.returning` method provides RETURNING support -that integrates with the "implicit identifier returning" feature and is automatically -utilized or de-utilized depending on backend. +.. seealso:: + + :ref:`server_side_version_counter` :ticket:`2793` @@ -909,9 +909,9 @@ immediately within the flush process. In 0.9, as a result of the version id enhancements, ``eager_defaults`` can now emit a RETURNING clause for these values, so on a backend with strong RETURNING support in particular Postgresql, the ORM can fetch newly generated default -and SQL expression values inline with the INSERT or UPDATE. The feature takes -place automatically when the target backend and :class:`.Table` supports -"implicit returning". +and SQL expression values inline with the INSERT or UPDATE. ``eager_defaults``, +when enabled, makes use of RETURNING automatically when the target backend +and :class:`.Table` supports "implicit returning". .. _change_2836: |