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authorMike Bayer <mike_mp@zzzcomputing.com>2020-01-04 13:34:45 -0500
committerMike Bayer <mike_mp@zzzcomputing.com>2020-01-04 13:34:45 -0500
commitd9dda8b94036dd5c76968f3ca0d3400f5d765894 (patch)
tree391f8968843b346887e1c3078df834f13c611fce
parent4b2a0ca7aef4a1af4a2cd26eaae3055e930f42b7 (diff)
downloadsqlalchemy-d9dda8b94036dd5c76968f3ca0d3400f5d765894.tar.gz
Add missing changelog file for #5074
The changelog file was missing from 0a8b11bb6528c38dc441caadc6eb2d25046fc376 / I00b656eb5ee03d87104257a214214617aacae16c. Fixes: #5074 Change-Id: Ic69fc6b4fb92ed133a14ba36f878f3f4740c565b
-rw-r--r--doc/build/changelog/unreleased_14/5074.rst23
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diff --git a/doc/build/changelog/unreleased_14/5074.rst b/doc/build/changelog/unreleased_14/5074.rst
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+.. change::
+ :tags: bug, orm
+ :tickets: 5074
+
+ The :class:`.Session` object no longer initates a
+ :class:`.SessionTransaction` object immediately upon construction or after
+ the previous transaction is closed; instead, "autobegin" logic now
+ initiates the new :class:`.SessionTransaction` on demand when it is next
+ needed. Rationale includes to remove reference cycles from a
+ :class:`.Session` that has been closed out, as well as to remove the
+ overhead incurred by the creation of :class:`.SessionTransaction` objects
+ that are often discarded immediately. This change affects the behavior of
+ the :meth:`.SessionEvents.after_transaction_create` hook in that the event
+ will be emitted when the :class:`.Session` first requires a
+ :class:`.SessionTransaction` be present, rather than whenever the
+ :class:`.Session` were created or the previous :class:`.SessionTransaction`
+ were closed. Interactions with the :class:`.Engine` and the database
+ itself remain unaffected.
+
+ .. seealso::
+
+ :ref:`change_5074`
+