# Setup
Suppose I have a table with two fields: a string primary key and a boolean
flag. I want to query multiple rows and then update the flag across all of
them, then commit my changes. I have a MySQL DB with the following DBAPI
(http://mysql-python.sourceforge.net/MySQLdb-1.2.2/public/MySQLdb-module.html).
## Model
class TestSQLTable(Base):
__tablename__ = 'test_table'
some_string_id = Column(String(32), nullable=False, primary_key=True)
flag = Column(Boolean, nullable=False, default=True)
# SQLAlchemy 1.0.12
In SQLAlchemy 1.0.12, the following worked:
sm = sessionmaker(
autocommit=False,
autoflush=True,
expire_on_commit=True,
bind=engine, # MySQL engine
)
session_factory = scoped_session(sm)
def modify_records(session, flag=False):
records = session.query(TestSQLTable).all()
for r in records:
r.flag = flag
session = session_factory()
modify_records(session)
session.commit()
# SQLAlchemy 1.1.13
Now, this does *not* work and causes a core dump. I am unable to tell what
change was made in 1.1 that causes this different behavior when reading the
["What's New in SQLAlchemy
1.1?"](http://docs.sqlalchemy.org/en/latest/changelog/migration_11.html)
guide.
If I do this in a Jupyter notebook, for instance, the kernel just crashes
on commit without any error.
However, this **does** work for just a single row:
def modify_record(session, flag=False):
record = session.query(TestSQLTable).first()
record.flag = flag
## Ways I have gotten this to work
### Add an explicit return
def modify_records(session, flag=False):
records = session.query(TestSQLTable).all()
for r in records:
r.flag = flag
return records # ADD THIS!
### Flush after each mutation
def modify_records(session, flag=False):
records = session.query(TestSQLTable).all()
for r in records:
r.flag = flag
session.flush() # ADD THIS!
### Restructure code so that the commit happens inside `modify_records`
This works, but is not the way the application is currently built and would
thus require a major refactor (b/c commit happens via a decorator).
# Main question
Why does this happen exactly for multiple records and why did this work in
1.0 but does not in 1.1?
Thanks in advance!
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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