利用redis协助mysql数据库搬迁

　　最近公司新项目上线，需要数据库搬迁，但新版本和老版本数据库差距比较大，关系也比较复杂。如果用传统办法，需要撰写很多mysql脚本，工程量虽然不大，但对于没有dba的公司来说，稍微有点难度。本人就勉为其难，用redis作为mysql中转站，先把原来的mysql数据转移到redis里面，再从redis转换到新的mysql。整个过程脉络清晰，脚本简单。

　　首先，公司之前的项目是，flask+sqlalchemy的方式，直接复制原来的model文件，稍微修改一下，就有以下代码。

 # coding:utf-8
 from sqlalchemy import create_engine, ForeignKey, Column, Integer, String, Text, DateTime, Boolean, and_, or_,\
     SmallInteger, func, Numeric, select, Float, Table, TIMESTAMP, DECIMAL, desc
 from sqlalchemy.orm import relationship, backref, sessionmaker, scoped_session
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.ext.hybrid import hybrid_property, hybrid_method, Comparator
 from sqlalchemy import event
 import redis
 import json

 mysql_info = "mysql://username:password@ip_address:3306/databasename?charset=utf8"
 redis_store = redis.Redis(host='127.0.0.1', port=6380, password='password', db=5)

 engine = create_engine(mysql_info, pool_recycle=7200)
 Base = declarative_base()

 class User(Base):
     __tablename__ = 'user'

     id = Column('id', Integer, primary_key=True)
     phone_number = Column('phone_number', String(11), index=True)
     password = Column('password', String(30))
     nickname = Column('nickname', String(30), index=True, nullable=True)
     headpic = Column('headpic', String(100), nullable=True)
     register_time = Column('register_time', DateTime, index=True)
     email = Column('email', String(50), default='', index=True)
     real_name = Column('real_name', String(50), default='', index=True)
     user_admin = Column('user_admin', Integer, index=True, default=0)
     rc_token = Column('rc_token', String(100))
     device_token = Column('device_token', String(100), unique=True, nullable=True)
     unit_id = Column('unit_id', Integer, ForeignKey('unit.id'))
     unit = relationship("Unit", backref=backref('users'))

     def to_dict(self):
         return dict(id=self.id, phone_number=self.phone_number,
                     password=self.password, nickname=self.nickname,
                     headpic=self.headpic, register_time=self.register_time.strftime('%Y-%m-%d %H:%M:%S'),
                     user_admin=self.user_admin, rc_token=self.rc_token,
                     unit_id=self.unit_id, device_token=self.device_token,
                     )

 class Group(Base):
     __tablename__ = 'groups'

     id = Column('id', Integer, primary_key=True)
     name = Column('name', String(100), index=True)
     address = Column('address', String(100), index=True, nullable=True)
     contact_person = Column('contactperson', String(30), nullable=True)
     contact_number = Column('contactnumber', String(30), nullable=True)
     unit_id = Column('unit_id', Integer, ForeignKey('unit.id'))
     unit = relationship('Unit', backref=backref('groups'))

 class Monitor(Base):
     __tablename__ = 'monitor'

     id = Column('id', Integer, primary_key=True)
     u_id = Column('sn_num', String(10), index=True)
     phone_num = Column('phone_num', String(20), index=True, nullable=True)
     name = Column('name', String(40), index=True, nullable=True)
     position = Column('position', String(40), nullable=True)
     join_time = Column('join_time', DateTime, index=True, nullable=True)
     group_id = Column('group_id', Integer, ForeignKey('groups.id'))
     group = relationship("Group", backref=backref('monitors'))
     longitude = Column('longitude', DECIMAL(12, 9), default=31.000000)
     latitude = Column('latitude', DECIMAL(12, 9), default=121.000000)

     def to_dict(self):
         unit_id = self.group.unit_id
         return dict(id=self.id, u_id=self.u_id, phone_num=self.phone_num, name=self.name,
                     position=self.position, join_time=self.join_time.strftime('%Y-%m-%d %H:%M:%S'), unit_id=unit_id,
                     longitude=str(self.longitude), latitude=str(self.latitude))

 class Unit(Base):
     __tablename__ = 'unit'

     id = Column('id', Integer, primary_key=True)
     name = Column('name', String(100), index=True, nullable=True)
     address = Column('address', String(100), index=True, nullable=True)
     contact_person = Column('contactperson', String(30), index=True, nullable=True)
     contact_number = Column('contactnumber', String(30), nullable=True)
     device_operation_password = Column('device_operation_password', String(4), nullable=True)
     rc_group_id = Column('rc_group_id', String(50), index=True, nullable=True)
     rc_group_name = Column('rc_group_name', String(50), index=True, nullable=True)
     longitude = Column('longitude', DECIMAL(12, 9), nullable=True)
     latitude = Column('latitude', DECIMAL(12, 9), nullable=True)
     active = Column('active', SmallInteger, index=True, default=0)

     def to_dict(self):
         return dict(id=self.id, name=self.name, address=self.address,
                     contact_person=self.contact_person, contact_number=self.contact_number,
                     device_operation_password=self.device_operation_password,
                     rc_group_id=self.rc_group_id, rc_group_name=self.rc_group_name,
                     longitude=str(self.longitude), latitude=str(self.latitude), active=self.active)

 db_session = scoped_session(sessionmaker(autocommit=False,
                                          autoflush=False,
                                          bind=engine))

 Base.query = db_session.query_property()

 def old_sql_2_redis():
     redis_store.flushdb()
     units = Unit.query.all()
     [redis_store.rpush('units', json.dumps(unit.to_dict())) for unit in units]

     users = User.query.all()
     [redis_store.rpush('users', json.dumps(user.to_dict())) for user in users]

     monitors = Monitor.query.all()
     [redis_store.rpush('monitors', json.dumps(monitor.to_dict())) for monitor in monitors]

 if __name__ == '__main__':
     old_sql_2_redis()

把原来的数据库复制到本地redis了，看查看里面的元素。比如user数据，直接建一个user的list，每个appened其json格式的数据就可以了。主要注意点就是，如果新版本的表中没有的字段，就不要写入的redis了。

第二步就是把本地redis里面的数据，放到新的数据库上。这边要注意以下，把需要修改的地方要标示出来，可能加了其他字段，这些字段没有默认值的话，要自己添加上。过程也比较简单。

 # coding:utf-8
 from sqlalchemy import create_engine, ForeignKey, Column, Integer, String, Text, DateTime, Boolean, and_, or_,\
     SmallInteger, func, Numeric, select, Float, Table, TIMESTAMP, DECIMAL, desc
 from sqlalchemy.orm import relationship, backref, sessionmaker, scoped_session
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.ext.hybrid import hybrid_property, hybrid_method, Comparator
 from sqlalchemy import event
 import redis
 import json
 import datetime
 import uuid

 mysql_info = "mysql://username:password@ip_address:3306/database_name?charset=utf8"
 redis_store = redis.Redis(host='127.0.0.1', port=6380, password='password', db=5)

 engine = create_engine(mysql_info, pool_recycle=7200)
 Base = declarative_base()

 class User(Base):
     __tablename__ = 'user'

     id = Column('id', Integer, primary_key=True)
     phone_number = Column('phone_number', String(11), index=True)
     password = Column('password', String(30))
     nickname = Column('nickname', String(30), index=True, nullable=True)
     headpic = Column('headpic', String(100), nullable=True)
     register_time = Column('register_time', DateTime, index=True, default=datetime.datetime.now)
     user_admin = Column('user_admin', SmallInteger, index=True, default=0)
     hidden_user = Column('hidden_user', SmallInteger, index=True, default=0)
     rc_token = Column('rc_token', String(100), nullable=True)
     device_token = Column('device_token', String(100), unique=True, nullable=True)
     unit_id = Column('unit_id', Integer, ForeignKey('unit.id'))
     unit = relationship('Unit', backref=backref('users'))

 class Monitor(Base):
     __tablename__ = 'monitor'

     id = Column('id', Integer, primary_key=True)
     # device_type 1代表灭弧 2代表电气火灾
     device_type = Column('device_type', SmallInteger, index=True, default=1)
     u_id = Column('sn_num', String(10), index=True)
     phone_num = Column('phone_num', String(20), index=True, nullable=True)
     name = Column('name', String(40), index=True)
     position = Column('position', String(40), nullable=True)
     join_time = Column('join_time', DateTime, index=True)
     longitude = Column('longitude', DECIMAL(12, 9), default=31.000000)
     latitude = Column('latitude', DECIMAL(12, 9), default=121.000000)
     unit_id = Column('unit_id', Integer, ForeignKey('unit.id'))

 class Unit(Base):
     __tablename__ = 'unit'

     id = Column('id', Integer, primary_key=True)
     name = Column('name', String(100), index=True)
     address = Column('address', String(100), index=True, nullable=True)
     contact_person = Column('contactperson', String(30), nullable=True)
     contact_number = Column('contactnumber', String(30), nullable=True)
     device_operation_password = Column(')
     rc_group_id = Column('rc_group_id', String(36), default=str(uuid.uuid1()))
     rc_group_name = Column('rc_group_name', String(50), nullable=True)
     longitude = Column('longitude', DECIMAL(12, 9), default=31.000000)
     latitude = Column('latitude', DECIMAL(12, 9), default=121.000000)
     active = Column('active', SmallInteger, index=True, default=0)
     is_group = Column('is_group', SmallInteger, index=True, default=0)
     parent_id = Column('parent_id', Integer, ForeignKey('unit.id'))

 db_session = scoped_session(sessionmaker(autocommit=False,
                                          autoflush=False,
                                          bind=engine))

 Base.query = db_session.query_property()

 def redis_2_new_sql():
     units_json = redis_store.lrange('units', 0, -1)
     units = [Unit(is_group=0, parent_id=None, **json.loads(unit_json)) for unit_json in units_json]
     [db_session.add(unit) for unit in units]
     try:
         db_session.commit()
     except Exception as e:
         print e
         db_session.rollback()
         return

     users_json = redis_store.lrange('users', 0, -1)
     users = [User(hidden_user=0, **json.loads(uer_json)) for uer_json in users_json]
     [db_session.add(user) for user in users]
     try:
         db_session.commit()
     except Exception as e:
         print e
         db_session.rollback()
         return

     monitors_json = redis_store.lrange('monitors', 0, -1)
     monitors = [Monitor(**json.loads(monitor_json)) for monitor_json in monitors_json]
     [db_session.add(monitor) for monitor in monitors]
     try:
         db_session.commit()
     except Exception as e:
         print e
         db_session.rollback()
         return

 if __name__ == '__main__':
     redis_2_new_sql()

整个过程相当简单，需要注意的就是，前后顺序，因为user和monitor都有一个外键指向unit，所以要先恢复unit表，这样就不会出错了。

看来以后我有新方法搬迁数据库了。