Add _extend_on deduplicating set for metadata.reflect()

The "extend_existing" option of :class:`.Table` reflection would
cause indexes and constraints to be doubled up in the case that the parameter
were used with :meth:`.MetaData.reflect` (as the automap extension does)
due to tables being reflected both within the foreign key path as well
as directly.  A new de-duplicating set is passed through within the
:meth:`.MetaData.reflect` sequence to prevent double reflection in this
way.

Change-Id: Ibf6650c1e76a44ccbe15765fd79df2fa53d6bac7
Fixes: #3861

1 files changed, 35 insertions, 1 deletions

diff --git a/test/engine/test_reflection.py b/test/engine/test_reflection.py
index 62568eb4a..869fd63e5 100644
--- a/test/engine/test_reflection.py
+++ b/test/engine/test_reflection.py
@@ -1,7 +1,8 @@
 import unicodedata
 import sqlalchemy as sa
 from sqlalchemy import schema, inspect
-from sqlalchemy import MetaData, Integer, String
+from sqlalchemy import MetaData, Integer, String, Index, ForeignKey, \
+    UniqueConstraint
 from sqlalchemy.testing import (
     ComparesTables, engines, AssertsCompiledSQL,
     fixtures, skip)
@@ -201,6 +202,39 @@ class ReflectionTest(fixtures.TestBase, ComparesTables):
         assert t4.c.z.type._type_affinity is String
         assert t4.c.q is old_q
 
+    @testing.provide_metadata
+    def test_extend_existing_reflect_all_dont_dupe_index(self):
+        m = self.metadata
+        d = Table(
+            "d", m, Column('id', Integer, primary_key=True),
+            Column('foo', String(50)),
+            Column('bar', String(50)),
+            UniqueConstraint('bar')
+        )
+        Index("foo_idx", d.c.foo)
+        Table(
+            "b", m, Column('id', Integer, primary_key=True),
+            Column('aid', ForeignKey('d.id'))
+        )
+        m.create_all()
+
+        m2 = MetaData()
+        m2.reflect(testing.db, extend_existing=True)
+
+        eq_(
+            len([idx for idx in m2.tables['d'].indexes
+                 if idx.name == 'foo_idx']),
+            1
+        )
+        if testing.requires.\
+                unique_constraint_reflection_no_index_overlap.enabled:
+            eq_(
+                len([
+                    const for const in m2.tables['d'].constraints
+                    if isinstance(const, UniqueConstraint)]),
+                1
+            )
+
     @testing.emits_warning(r".*omitted columns")
     @testing.provide_metadata
     def test_include_columns_indexes(self):