Traps in PonyORM

website: http://ponyorm.com/ useage: http://doc.ponyorm.com/ tracks: http://stackoverflow.com/questions/16115713/how-pony-orm-does-its-tricks/16118756#16118756

优势及好玩的地方就不介绍了，说说可能遇到的陷阱

##more test_pony.py #!/usr/bin/env python #-- coding: utf-8 --

from pony.orm import Database, Required, sql_debug
from pony.orm import select, commit

db = Database('sqlite', ':memory:')


class User(db.Entity):
    email = Required(unicode)
    password = Required(unicode)

db.generate_mapping(create_tables=True)
sql_debug(True)

for i in range(2):
    user = User(email='1', password='1')
    commit()
    users = list(select(u for u in User))
    print users
    print id(users)

users = list(select(u for u in User))
print users

##python test_pony.py OPTIMISTIC ROLLBACK

INSERT INTO "User" ("email", "password") VALUES (?, ?)
[u'1', u'1']

COMMIT

SELECT "u"."id", "u"."email", "u"."password"
FROM "User" "u"

[User[1]]
4453021024
OPTIMISTIC ROLLBACK

INSERT INTO "User" ("email", "password") VALUES (?, ?)
[u'1', u'1']

COMMIT

[User[1]]
4453021600
SELECT "u"."id", "u"."email", "u"."password"
FROM "User" "u"

[User[1], User[2]]

设置为 debug 模式，可以看到 for 循环中 select 查询只有一次，这不是我们期望的

此现象也出现在单进程的 tornado server 中, handler GET 获取所有结果，POST 添加新内容，但每次得到的仍然是第一次获取的

可以改用 User.select_by_sql 这种方式

update at 23:30 提交 BUG 两小时后，作者就 fix 了 https://github.com/ponyorm/pony/commit/42ec42ab444948c407b5566752b1a51ac8c075ac