From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Thu, 2 Jun 2016 17:52:27 +0000 (-0400)
Subject: Skip UniqueConstraint marked by unique=True in tometadata
X-Git-Tag: rel_1_0_14~13^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d318139fdc4c0c381fc5618d73b9b33e0d73a4f5;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

Skip UniqueConstraint marked by unique=True in tometadata

Fixes an issue where a Column would be copied with unique=True
and at the same time the UniqueConstraint would also be copied,
leading to duplicate UniqueConstraints in the target table,
when tometadata() is used.   Imitates the same logic used
by index=True/Index to avoid duplicates.  For some reason
a fix was implemented for Index long ago but never for
UniqueConstraint.

Change-Id: Ie622ee912a6fb8bf0ea900a8b09d78c7ebc79fc0
Fixes: #3721
(cherry picked from commit afb466fb8bd9c2f8709e79fd0fce422b83ff1d6b)
---

diff --git a/doc/build/changelog/changelog_10.rst b/doc/build/changelog/changelog_10.rst
index 5f9521c479..b59ab392e5 100644
--- a/doc/build/changelog/changelog_10.rst
+++ b/doc/build/changelog/changelog_10.rst
@@ -18,6 +18,14 @@
 .. changelog::
     :version: 1.0.14
 
+    .. change::
+        :tags: bug, sql
+        :tickets: 3721
+
+        Fixed bug whereby :meth:`.Table.tometadata` would make a duplicate
+        :class:`.UniqueConstraint` for each :class:`.Column` object that
+        featured the ``unique=True`` parameter.
+
     .. change::
         :tags: bug, engine, postgresql
         :tickets: 3716
diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py
index f18102e05f..f9c6d05a91 100644
--- a/lib/sqlalchemy/sql/schema.py
+++ b/lib/sqlalchemy/sql/schema.py
@@ -862,8 +862,14 @@ class Table(DialectKWArgs, SchemaItem, TableClause):
                         schema if referred_schema == self.schema else None)
                 table.append_constraint(
                     c.copy(schema=fk_constraint_schema, target_table=table))
-
             elif not c._type_bound:
+                # skip unique constraints that would be generated
+                # by the 'unique' flag on Column
+                if isinstance(c, UniqueConstraint) and \
+                    len(c.columns) == 1 and \
+                        list(c.columns)[0].unique:
+                    continue
+
                 table.append_constraint(
                     c.copy(schema=schema, target_table=table))
         for index in self.indexes:
diff --git a/test/sql/test_metadata.py b/test/sql/test_metadata.py
index 1a4988aca5..ed014af3e2 100644
--- a/test/sql/test_metadata.py
+++ b/test/sql/test_metadata.py
@@ -1111,6 +1111,34 @@ class ToMetaDataTest(fixtures.TestBase, ComparesTables):
         eq_(str(table_c.join(table2_c).onclause),
             'mytable.myid = othertable.myid')
 
+    def test_unique_true_flag(self):
+        meta = MetaData()
+
+        table = Table('mytable', meta, Column('x', Integer, unique=True))
+
+        m2 = MetaData()
+
+        t2 = table.tometadata(m2)
+
+        eq_(
+            len([
+                const for const
+                in t2.constraints
+                if isinstance(const, UniqueConstraint)]),
+            1
+        )
+
+    def test_index_true_flag(self):
+        meta = MetaData()
+
+        table = Table('mytable', meta, Column('x', Integer, index=True))
+
+        m2 = MetaData()
+
+        t2 = table.tometadata(m2)
+
+        eq_(len(t2.indexes), 1)
+
 
 class InfoTest(fixtures.TestBase):
     def test_metadata_info(self):