- Added get_pk_constraint() to reflection.Inspector, similar

to get_primary_keys() except returns a dict that includes the
name of the constraint, for supported backends (PG so far).
[ticket:1769]
- Postgresql reflects the name of primary key constraints,
if one exists.  [ticket:1769]

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 312ae9aa8..72251c8d5 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -1006,6 +1006,27 @@ class PGDialect(default.DefaultDialect):
         return primary_keys
 
     @reflection.cache
+    def get_pk_constraint(self, connection, table_name, schema=None, **kw):
+        cols = self.get_primary_keys(connection, table_name, schema=schema, **kw)
+        
+        table_oid = self.get_table_oid(connection, table_name, schema,
+                                       info_cache=kw.get('info_cache'))
+
+        PK_CONS_SQL = """
+        SELECT conname
+           FROM  pg_catalog.pg_constraint r
+           WHERE r.conrelid = :table_oid AND r.contype = 'p'
+           ORDER BY 1
+        """
+        t = sql.text(PK_CONS_SQL, typemap={'conname':sqltypes.Unicode})
+        c = connection.execute(t, table_oid=table_oid)
+        name = c.scalar()
+        return {
+            'constrained_columns':cols,
+            'name':name
+        }
+
+    @reflection.cache
     def get_foreign_keys(self, connection, table_name, schema=None, **kw):
         preparer = self.identifier_preparer
         table_oid = self.get_table_oid(connection, table_name, schema,