OpenStack and Sqlalchemy

很感謝這篇文章

http://www.dangtrinh.com/2013/06/sqlalchemy-python-module-with-mysql.html

OpneStack的Sqlalchemy

要用Python我們的確應該看看OpenStack提供了什麼樣的幫助，首先 OpenStack定義的DB schema都放在這個檔案下

nova/nova/db/sqlalchemy/models.py

我們來看一下他是用什麼方式定義的，將定義放在Class中。

class InstanceTypes(BASE, NovaBase):
    """Represents possible flavors for instances.

    Note: instance_type and flavor are synonyms and the term instance_type is
    deprecated and in the process of being removed.
    """
    __tablename__ = "instance_types"

    __table_args__ = (
        schema.UniqueConstraint("flavorid", "deleted",
                                name="uniq_instance_types0flavorid0deleted"),
        schema.UniqueConstraint("name", "deleted",
                                name="uniq_instance_types0name0deleted")
    )

    # Internal only primary key/id
    id = Column(Integer, primary_key=True)
    name = Column(String(255))
    memory_mb = Column(Integer, nullable=False)
    vcpus = Column(Integer, nullable=False)
    root_gb = Column(Integer)
    ephemeral_gb = Column(Integer)
    # Public facing id will be renamed public_id
    flavorid = Column(String(255))
    swap = Column(Integer, nullable=False, default=0)
    rxtx_factor = Column(Float, default=1)
    vcpu_weight = Column(Integer)
    disabled = Column(Boolean, default=False)
    is_public = Column(Boolean, default=True)

我們再看看OpenStack import了什麼

from sqlalchemy import (Column, Index, Integer, BigInteger, Enum, String,
                        schema, Unicode)
from sqlalchemy.dialects.mysql import MEDIUMTEXT
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import orm
from sqlalchemy import ForeignKey, DateTime, Boolean, Text, Float

from nova.db.sqlalchemy import types