From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Mon, 4 Mar 2019 14:37:08 +0000 (-0500)
Subject: Clarify and correct PostgreSQL server default comparison for py37
X-Git-Tag: rel_1_0_8~2^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7e95b81548dde1c363945cd3937b27af90f20459;p=thirdparty%2Fsqlalchemy%2Falembic.git

Clarify and correct PostgreSQL server default comparison for py37

Fixed issue where server default comparison on the PostgreSQL dialect would
fail for a blank string on Python 3.7 only, due to a change in regular
expression behavior in Python 3.7.

Change-Id: Iac62ba77622d63ad0c2666cf20a4622f98cf14e6
Fixes: #541
---

diff --git a/alembic/ddl/postgresql.py b/alembic/ddl/postgresql.py
index a8e332ec..255c7e62 100644
--- a/alembic/ddl/postgresql.py
+++ b/alembic/ddl/postgresql.py
@@ -68,19 +68,22 @@ class PostgresqlImpl(DefaultImpl):
         if None in (conn_col_default, rendered_metadata_default):
             return not defaults_equal
 
+        if compat.py2k:
+            # look for a python 2 "u''" string and filter
+            m = re.match(r"^u'(.*)'$", rendered_metadata_default)
+            if m:
+                rendered_metadata_default = "'%s'" % m.group(1)
+
+        # check for unquoted string and quote for PG String types
         if (
+            not isinstance(inspector_column.type, Numeric) and
             metadata_column.server_default is not None
             and isinstance(
                 metadata_column.server_default.arg, compat.string_types
             )
-            and not re.match(r"^'.+'$", rendered_metadata_default)
-            and not isinstance(inspector_column.type, Numeric)
+            and not re.match(r"^'.*'$", rendered_metadata_default)
         ):
-            # don't single quote if the column type is float/numeric,
-            # otherwise a comparison such as SELECT 5 = '5.0' will fail
-            rendered_metadata_default = re.sub(
-                r"^u?'?|'?$", "'", rendered_metadata_default
-            )
+            rendered_metadata_default = "'%s'" % rendered_metadata_default
 
         return not self.connection.scalar(
             "SELECT %s = %s" % (conn_col_default, rendered_metadata_default)
diff --git a/docs/build/unreleased/541.rst b/docs/build/unreleased/541.rst
new file mode 100644
index 00000000..9da38503
--- /dev/null
+++ b/docs/build/unreleased/541.rst
@@ -0,0 +1,8 @@
+.. change::
+   :tags: bug, autogenerate, postgresql, py3k
+   :tickets: 541
+
+   Fixed issue where server default comparison on the PostgreSQL dialect would
+   fail for a blank string on Python 3.7 only, due to a change in regular
+   expression behavior in Python 3.7.
+
diff --git a/tests/test_postgresql.py b/tests/test_postgresql.py
index 73300f5e..9a0e8f3a 100644
--- a/tests/test_postgresql.py
+++ b/tests/test_postgresql.py
@@ -506,6 +506,12 @@ class PostgresqlDefaultCompareTest(TestBase):
             None, col, rendered, cols[0]["default"]
         )
 
+    def test_compare_string_blank_default(self):
+        self._compare_default_roundtrip(String(8), '')
+
+    def test_compare_string_nonblank_default(self):
+        self._compare_default_roundtrip(String(8), 'hi')
+
     def test_compare_interval_str(self):
         # this form shouldn't be used but testing here
         # for compatibility