- The Postgresql :class:`.postgresql.ENUM` type will emit a

DROP TYPE instruction when a plain ``table.drop()`` is called,
assuming the object is not associated directly with a
:class:`.MetaData` object.   In order to accomodate the use case of
an enumerated type shared between multiple tables, the type should
be associated directly with the :class:`.MetaData` object; in this
case the type will only be created at the metadata level, or if
created directly.  The rules for create/drop of
Postgresql enumerated types have been highly reworked in general.
fixes #3319

2 files changed, 69 insertions, 0 deletions

diff --git a/doc/build/changelog/changelog_10.rst b/doc/build/changelog/changelog_10.rst
index 1776625f8..ca9aa1b7e 100644
--- a/doc/build/changelog/changelog_10.rst
+++ b/doc/build/changelog/changelog_10.rst
@@ -24,6 +24,24 @@
     on compatibility concerns, see :doc:`/changelog/migration_10`.
 
     .. change::
+        :tags: bug, postgresql
+        :tickets: 3319
+
+        The Postgresql :class:`.postgresql.ENUM` type will emit a
+        DROP TYPE instruction when a plain ``table.drop()`` is called,
+        assuming the object is not associated directly with a
+        :class:`.MetaData` object.   In order to accomodate the use case of
+        an enumerated type shared between multiple tables, the type should
+        be associated directly with the :class:`.MetaData` object; in this
+        case the type will only be created at the metadata level, or if
+        created directly.  The rules for create/drop of
+        Postgresql enumerated types have been highly reworked in general.
+
+        .. seealso::
+
+            :ref:`change_3319`
+
+    .. change::
         :tags: feature, orm
         :tickets: 3317
 
diff --git a/doc/build/changelog/migration_10.rst b/doc/build/changelog/migration_10.rst
index 66b385cc2..e4f1e0e25 100644
--- a/doc/build/changelog/migration_10.rst
+++ b/doc/build/changelog/migration_10.rst
@@ -1767,6 +1767,57 @@ reflection from temp tables as well, which is :ticket:`3203`.
 Dialect Improvements and Changes - Postgresql
 =============================================
 
+.. _change_3319:
+
+Overhaul of ENUM type create/drop rules
+---------------------------------------
+
+The rules for Postgresql :class:`.postgresql.ENUM` have been made more strict
+with regards to creating and dropping of the TYPE.
+
+An :class:`.postgresql.ENUM` that is created **without** being explicitly
+associated with a :class:`.MetaData` object will be created *and* dropped
+corresponding to :meth:`.Table.create` and :meth:`.Table.drop`::
+
+    table = Table('sometable', metadata,
+        Column('some_enum', ENUM('a', 'b', 'c', name='myenum'))
+    )
+
+    table.create(engine)  # will emit CREATE TYPE and CREATE TABLE
+    table.drop(engine)  # will emit DROP TABLE and DROP TYPE - new for 1.0
+
+This means that if a second table also has an enum named 'myenum', the
+above DROP operation will now fail.    In order to accomodate the use case
+of a common shared enumerated type, the behavior of a metadata-associated
+enumeration has been enhanced.
+
+An :class:`.postgresql.ENUM` that is created **with** being explicitly
+associated with a :class:`.MetaData` object will *not* be created *or* dropped
+corresponding to :meth:`.Table.create` and :meth:`.Table.drop`, with
+the exception of :meth:`.Table.create` called with the ``checkfirst=True``
+flag::
+
+    my_enum = ENUM('a', 'b', 'c', name='myenum', metadata=metadata)
+
+    table = Table('sometable', metadata,
+        Column('some_enum', my_enum)
+    )
+
+    # will fail: ENUM 'my_enum' does not exist
+    table.create(engine)
+
+    # will check for enum and emit CREATE TYPE
+    table.create(engine, checkfirst=True)
+
+    table.drop(engine)  # will emit DROP TABLE, *not* DROP TYPE
+
+    metadata.drop_all(engine) # will emit DROP TYPE
+
+    metadata.create_all(engine) # will emit CREATE TYPE
+
+
+:ticket:`3319`
+
 New Postgresql Table options
 -----------------------------