Added custom guid type so we can choose the most efficient backend DB type easily.

1 files changed, 38 insertions, 2 deletions

diff --git a/nova/db/sqlalchemy/models.py b/nova/db/sqlalchemy/models.py
index a7725ac3c..7ec96bc6d 100644
--- a/nova/db/sqlalchemy/models.py
+++ b/nova/db/sqlalchemy/models.py
@@ -22,12 +22,14 @@ SQLAlchemy models for nova data.
 import datetime
 import uuid
 
-from sqlalchemy.orm import relationship, backref, object_mapper
 from sqlalchemy import Column, Integer, Float, String, schema
 from sqlalchemy import ForeignKey, DateTime, Boolean, Text
+from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import relationship, backref, object_mapper
 from sqlalchemy.schema import ForeignKeyConstraint
+from sqlalchemy.types import TypeDecorator, CHAR
 
 from nova.db.sqlalchemy.session import get_session
 
@@ -44,6 +46,40 @@ def make_uuid():
     return uuid.uuid1().hex
 
 
+class GUID(TypeDecorator):
+    """Platform-independent GUID type.
+
+    Uses Postgresql's UUID type, otherwise uses
+    CHAR(32), storing as stringified hex values.
+
+    """
+    impl = CHAR
+
+    def load_dialect_impl(self, dialect):
+        if dialect.name == 'postgresql':
+            return dialect.type_descriptor(UUID())
+        else:
+            return dialect.type_descriptor(CHAR(32))
+
+    def process_bind_param(self, value, dialect):
+        if value is None:
+            return value
+        elif dialect.name == 'postgresql':
+            return str(value)
+        else:
+            if not isinstance(value, uuid.UUID):
+                return "%.32x" % uuid.UUID(value)
+            else:
+                # hexstring
+                return "%.32x" % value
+
+    def process_result_value(self, value, dialect):
+        if value is None:
+            return value
+        else:
+            return uuid.UUID(value).hex
+
+
 class NovaBase(object):
     """Base class for Nova Models."""
     __table_args__ = {'mysql_engine': 'InnoDB'}
@@ -169,7 +205,7 @@ class Certificate(BASE, NovaBase):
 class Instance(BASE, NovaBase):
     """Represents a guest vm."""
     __tablename__ = 'instances'
-    id = Column(String(32), primary_key=True, default=make_uuid)
+    id = Column(GUID, primary_key=True, default=make_uuid)
 
     @property
     def name(self):