Можете да използвате SQLalchemy API за отражение .
За да получите уникалните ограничения, пуснете get_unique_constraints .
Първичните ключове са уникални, така че трябва да издадете get_pk_constraint също.
таблица, създадена с:
CREATE TABLE user (
id INTEGER NOT NULL,
name VARCHAR(255),
email VARCHAR(255),
login VARCHAR(255),
PRIMARY KEY (id),
UNIQUE (email),
UNIQUE (login)
)
пример:
from sqlalchemy import create_engine
from sqlalchemy.engine.reflection import Inspector
# engine = create_engine(...)
insp = Inspector.from_engine(engine)
print "PK: %r" % insp.get_pk_constraint("user")
print "UNIQUE: %r" % insp.get_unique_constraints("user")
изход:
PK: {'name': None, 'constrained_columns': [u'login']}
UNIQUE: [{'column_names': [u'email'], 'name': None}, {'column_names': [u'login'], 'name': None}]
Можете да проверите уникалните ограничения чрез:
pk = insp.get_pk_constraint("user")['constrained_columns']
unique = map(lambda x: x['column_names'], insp.get_unique_constraints("user"))
for column in ['name', 'id', 'email', 'login']:
print "Column %r has an unique constraint: %s" %(column, [column] in [pk]+unique)
изход:
Column 'name' has an unique constraint: False
Column 'id' has an unique constraint: True
Column 'email' has an unique constraint: True
Column 'login' has an unique constraint: True
Актуализация 01
Кодът по-горе проверява само ограничение за колони на вече създадена таблица, ако искате да проверите колоните преди създаването е по-просто:
from sqlalchemy import create_engine, Column, types
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, scoped_session
Base = declarative_base()
class User(Base):
__tablename__ = "user"
id = Column(types.Integer, primary_key=True)
name = Column(types.String(255))
email = Column(types.String(255), unique=True)
login = Column(types.String(255), unique=True)
# do not create any table
#engine = create_engine('sqlite:///:memory:', echo=True)
#session = scoped_session(sessionmaker(bind=engine))
#Base.metadata.create_all(engine)
# check if column is (any) a primary_key or has unique constraint
# Note1: You can use User.__table__.c too, it is a alias to columns
# Note2: If you don't want to use __table__, you could use the reflection API like:
# >>> from sqlalchemy.inspection import inspect
# >>> columns = inspect(User).columns
result = dict([(c.name, any([c.primary_key, c.unique])) for c in User.__table__.columns])
print(result)
изход:
{'email': True, 'login': True, 'id': True, 'name': False}
Ако искате да проверите само някои колони, можете да направите само:
for column_name in ['name', 'id', 'email', 'login']:
c = User.__table__.columns.get(column_name)
print("Column %r has an unique constraint: %s" %(column_name, any([c.primary_key, c.unique])))
изход:
Column 'name' has an unique constraint: False
Column 'id' has an unique constraint: True
Column 'email' has an unique constraint: True
Column 'login' has an unique constraint: True