Use pg_get_constraintdef for CHECK constraint reflection

Revised the query used when reflecting CHECK constraints to make use of the
``pg_get_constraintdef`` function, as the ``consrc`` column is being
deprecated in PG 12.  Thanks to John A Stevenson for the tip.

Fixes: #4463
Change-Id: Ie0ee9bdfddb0635db72b35c2e2e4b27f154162fd

1 files changed, 15 insertions, 0 deletions

diff --git a/test/dialect/postgresql/test_reflection.py b/test/dialect/postgresql/test_reflection.py
index 311835dae..ae1dff6d0 100644
--- a/test/dialect/postgresql/test_reflection.py
+++ b/test/dialect/postgresql/test_reflection.py
@@ -28,6 +28,7 @@ from sqlalchemy.dialects.postgresql import TSRANGE
 from sqlalchemy.engine import reflection
 from sqlalchemy.sql.schema import CheckConstraint
 from sqlalchemy.testing import fixtures
+from sqlalchemy.testing import mock
 from sqlalchemy.testing.assertions import assert_raises
 from sqlalchemy.testing.assertions import AssertsExecutionResults
 from sqlalchemy.testing.assertions import eq_
@@ -1424,6 +1425,20 @@ class ReflectionTest(fixtures.TestBase):
             },
         )
 
+    def test_reflect_check_warning(self):
+        conn = mock.Mock(
+            execute=lambda *arg, **kw: mock.Mock(
+                fetchall=lambda: [("some name", "NOTCHECK foobar")]
+            )
+        )
+        with mock.patch.object(
+            testing.db.dialect, "get_table_oid", lambda *arg, **kw: 1
+        ):
+            with testing.expect_warnings(
+                "Could not parse CHECK constraint text: 'NOTCHECK foobar'"
+            ):
+                testing.db.dialect.get_check_constraints(conn, "foo")
+
 
 class CustomTypeReflectionTest(fixtures.TestBase):
     class CustomType(object):