From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Thu, 5 Nov 2020 13:22:18 +0000 (-0500)
Subject: Copy column that's already attached
X-Git-Tag: rel_1_5_0~17^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a41d5e604fbea1e4c1723db9b826b394c702e34b;p=thirdparty%2Fsqlalchemy%2Falembic.git

Copy column that's already attached

Modified the ``add_column()`` operation such that the ``Column`` object in
use is shallow copied to a new instance if that ``Column`` is already
attached to a ``table()`` or ``Table``. This accommodates for the change
made in SQLAlchemy issue #5618 which prohibits a ``Column`` from being
associated with multiple ``table()`` objects. This resumes support for
using a ``Column`` inside of an Alembic operation that already refers to a
parent ``table()`` or ``Table`` as well as allows operation objects just
autogenerated to work.

Change-Id: Idc6933cf0da40373f4f270d75883995822c072f0
Fixes: #753
---

diff --git a/alembic/operations/toimpl.py b/alembic/operations/toimpl.py
index 30edd849..c6dbafbf 100644
--- a/alembic/operations/toimpl.py
+++ b/alembic/operations/toimpl.py
@@ -127,6 +127,9 @@ def add_column(operations, operation):
     schema = operation.schema
     kw = operation.kw
 
+    if column.table is not None:
+        column = column.copy()
+
     t = operations.schema_obj.table(table_name, column, schema=schema)
     operations.impl.add_column(table_name, column, schema=schema, **kw)
 
diff --git a/docs/build/unreleased/753.rst b/docs/build/unreleased/753.rst
new file mode 100644
index 00000000..687a8518
--- /dev/null
+++ b/docs/build/unreleased/753.rst
@@ -0,0 +1,12 @@
+.. change::
+    :tags: bug, operations
+    :tickets: 753
+
+    Modified the ``add_column()`` operation such that the ``Column`` object in
+    use is shallow copied to a new instance if that ``Column`` is already
+    attached to a ``table()`` or ``Table``. This accommodates for the change
+    made in SQLAlchemy issue #5618 which prohibits a ``Column`` from being
+    associated with multiple ``table()`` objects. This resumes support for
+    using a ``Column`` inside of an Alembic operation that already refers to a
+    parent ``table()`` or ``Table`` as well as allows operation objects just
+    autogenerated to work.
diff --git a/tests/test_op.py b/tests/test_op.py
index acd329ef..7b8dc027 100644
--- a/tests/test_op.py
+++ b/tests/test_op.py
@@ -7,6 +7,7 @@ from sqlalchemy import event
 from sqlalchemy import exc
 from sqlalchemy import ForeignKey
 from sqlalchemy import Integer
+from sqlalchemy import MetaData
 from sqlalchemy import String
 from sqlalchemy import Table
 from sqlalchemy.sql import column
@@ -111,6 +112,14 @@ class OpTest(TestBase):
         op.add_column("t1", Column("c1", Integer, nullable=False))
         context.assert_("ALTER TABLE t1 ADD COLUMN c1 INTEGER NOT NULL")
 
+    def test_add_column_already_attached(self):
+        context = op_fixture()
+        c1 = Column("c1", Integer, nullable=False)
+        Table("t", MetaData(), c1)
+
+        op.add_column("t1", c1)
+        context.assert_("ALTER TABLE t1 ADD COLUMN c1 INTEGER NOT NULL")
+
     def test_add_column_w_check(self):
         context = op_fixture()
         op.add_column(