I want to return the last inserted value for an auto_increment field in MySQL.
I have seen examples that mention the use of session.flush()
to add the record and then retrieve the id. However that always seems to return 0.
I have also seen examples that mention the use of session.refresh() but that raises the following error:
InvalidRequestError: Could not refresh instance '<MyModel....>'
My code looks something like this:
class Foo(Base):
__tablename__ = 'tblfoo'
__table_args__ = {'mysql_engine':'InnoDB'}
ModelID = Column(INTEGER(unsigned=True), default=0, primary_key=True, autoincrement=True)
ModelName = Column(Unicode(255), nullable=True, index=True)
ModelMemo = Column(Unicode(255), nullable=True)
f = Foo(ModelName='Bar', ModelMemo='Foo')
session.add(f)
session.flush()
At this point, the object f has been pushed to the DB, and has been automatically assigned a unique primary key id. However, I can't seem to find a way to obtain the value to use in some additional operations. I would like to do the following:
my_new_id = f.ModelID
I know I could simply execute another query to lookup the ModelID based on other parameters but I would prefer not to if at all possible.
The problem is you are setting defaul
for the auto increment. So when it run the insert into query the log of server is
2011-12-21 13:44:26,561 INFO sqlalchemy.engine.base.Engine.0x...1150 INSERT INTO tblfoo (`ModelID`, `ModelName`, `ModelMemo`) VALUES (%s, %s, %s)
2011-12-21 13:44:26,561 INFO sqlalchemy.engine.base.Engine.0x...1150 (0, 'Bar', 'Foo')
ID : 0
So the output is 0
which is the default value and which is passed because you are setting default value for autoincrement
column.
If I run same code without default
then it give the correct output.
Please try this code
from sqlalchemy import create_engine
engine = create_engine('mysql://test:test@localhost/test1', echo=True)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind=engine)
session = Session()
from sqlalchemy import Column, Integer, Unicode
class Foo(Base):
__tablename__ = 'tblfoo'
__table_args__ = {'mysql_engine':'InnoDB'}
ModelID = Column(Integer, primary_key=True, autoincrement=True)
ModelName = Column(Unicode(255), nullable=True, index=True)
ModelMemo = Column(Unicode(255), nullable=True)
Base.metadata.create_all(engine)
f = Foo(ModelName='Bar', ModelMemo='Foo')
session.add(f)
session.flush()
print "ID :", f.ModelID