- Revised this very old issue where the Postgresql "get primary key"

reflection query were updated to take into account primary key constraints
that were renamed; the newer query fails on very old versions of
Postgresql such as version 7, so the old query is restored in those cases
when server_version_info < (8, 0) is detected. #2291

2 files changed, 25 insertions, 1 deletions

diff --git a/doc/build/changelog/changelog_08.rst b/doc/build/changelog/changelog_08.rst
index e45abad56..4f07c1c65 100644
--- a/doc/build/changelog/changelog_08.rst
+++ b/doc/build/changelog/changelog_08.rst
@@ -12,6 +12,16 @@
     :version: 0.8.5
 
     .. change::
+        :tags: bug, postgresql
+        :tickets: 2291
+
+        Revised this very old issue where the Postgresql "get primary key"
+        reflection query were updated to take into account primary key constraints
+        that were renamed; the newer query fails on very old versions of
+        Postgresql such as version 7, so the old query is restored in those cases
+        when server_version_info < (8, 0) is detected.
+
+    .. change::
         :tags: bug, sql
         :tickets: 2957
         :versions: 0.9.3
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 29584d1eb..1b5927dbd 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -2026,7 +2026,21 @@ class PGDialect(default.DefaultDialect):
         table_oid = self.get_table_oid(connection, table_name, schema,
                                        info_cache=kw.get('info_cache'))
 
-        if self.server_version_info < (8, 4):
+        if self.server_version_info < (8, 0):
+            # the shortcoming of this query is that it will
+            # not detect a PK constraint that has been renamed.
+            # This query was removed with #2291, however it was reported
+            # that the newer queries do not work with PG 7 so here
+            # it is restored when old PG versions are detected.
+            PK_SQL = """
+              SELECT attname FROM pg_attribute
+              WHERE attrelid = (
+                 SELECT indexrelid FROM pg_index i
+                 WHERE i.indrelid = :table_oid
+                 AND i.indisprimary = 't')
+              ORDER BY attnum
+            """
+        elif self.server_version_info < (8, 4):
             # unnest() and generate_subscripts() both introduced in
             # version 8.4
             PK_SQL = """