Add enforcement for foreign key contraints with sqlite

Fixes bug 1171732

When creating an engine the called can indicate whether or
not to enforce the constraints for sqlite.

Change-Id: I1d5820376f60388c084afea500f807cd25541800

1 files changed, 22 insertions, 5 deletions

diff --git a/openstack/common/db/sqlalchemy/session.py b/openstack/common/db/sqlalchemy/session.py
index c719063..99439f4 100644
--- a/openstack/common/db/sqlalchemy/session.py
+++ b/openstack/common/db/sqlalchemy/session.py
@@ -248,6 +248,7 @@ from eventlet import greenthread
 from oslo.config import cfg
 from sqlalchemy import exc as sqla_exc
 import sqlalchemy.interfaces
+from sqlalchemy.interfaces import PoolListener
 import sqlalchemy.orm
 from sqlalchemy.pool import NullPool, StaticPool
 from sqlalchemy.sql.expression import literal_column
@@ -317,12 +318,25 @@ def set_defaults(sql_connection, sqlite_db):
                      sqlite_db=sqlite_db)
 
 
-def get_session(autocommit=True, expire_on_commit=False):
+class SqliteForeignKeysListener(PoolListener):
+    """
+    Ensures that the foreign key constraints are enforced in SQLite.
+
+    The foreign key constraints are disabled by default in SQLite,
+    so the foreign key constraints will be enabled here for every
+    database connection
+    """
+    def connect(self, dbapi_con, con_record):
+        dbapi_con.execute('pragma foreign_keys=ON')
+
+
+def get_session(autocommit=True, expire_on_commit=False,
+                sqlite_fk=False):
     """Return a SQLAlchemy session."""
     global _MAKER
 
     if _MAKER is None:
-        engine = get_engine()
+        engine = get_engine(sqlite_fk=sqlite_fk)
         _MAKER = get_maker(engine, autocommit, expire_on_commit)
 
     session = _MAKER()
@@ -439,11 +453,12 @@ def _wrap_db_error(f):
     return _wrap
 
 
-def get_engine():
+def get_engine(sqlite_fk=False):
     """Return a SQLAlchemy engine."""
     global _ENGINE
     if _ENGINE is None:
-        _ENGINE = create_engine(CONF.sql_connection)
+        _ENGINE = create_engine(CONF.sql_connection,
+                                sqlite_fk=sqlite_fk)
     return _ENGINE
 
 
@@ -500,7 +515,7 @@ def _is_db_connection_error(args):
     return False
 
 
-def create_engine(sql_connection):
+def create_engine(sql_connection, sqlite_fk=False):
     """Return a new SQLAlchemy engine."""
     connection_dict = sqlalchemy.engine.url.make_url(sql_connection)
 
@@ -517,6 +532,8 @@ def create_engine(sql_connection):
         engine_args['echo'] = True
 
     if "sqlite" in connection_dict.drivername:
+        if sqlite_fk:
+            engine_args["listeners"] = [SqliteForeignKeysListener()]
         engine_args["poolclass"] = NullPool
 
         if CONF.sql_connection == "sqlite://":