SQLAlchemy的count很慢

http://docs.sqlalchemy.org/en/rel_0_8/orm/tutorial.html#counting

uall = User.query.count()
很慢 (subquery的關係?)

session.query(func.count(User.id)).scalar()
快多了

232,053的資料, 用time.time() 算

count(): 4.53022193909 sec
func.count: 0.17828607559 sec

[SQLAlchemy] 不用primary key的table

table沒有設pirmary key會出現這個錯誤:

sqlalchemy.exc.ArgumentError: Mapper Mapper|FooTable|foo_table could not assemble any primary key columns for mapped table 'foo_table'

mapper要設:

"primary_key":(col1, col2)}

[SQLAlchemy] foreign key constraint 問題

以不delete, SET NULL為例:

1. database level
db.Column(db.Integer, ForeignKey(db.ForeignKey('category.id',ondelete='SET NULL')))

2. pythen level
db.relationship(passive_deletes=True)