Using bulk_update_mappings in SQLAlchemy to update multiple rows with different values

Question

I have two tables Foo and Bar. I just added a new column x to the Bar table which has to be populated using values in Foo

class Foo(Base):
    __tab         


        

Answer 1

The approach is correct in terms of usage. The only thing I would change is something like below

mappings = []
i = 0

for b, foo_x in session.query(Bar, Foo.x).join(Foo, Foo.id==Bar.foo_id):
    info = {'id':b.id, 'x': foo_x}
    mappings.append(info)
    i = i + 1
    if i % 10000 == 0:
        session.bulk_update_mappings(Bar, mappings)
        session.flush()
        session.commit()
        mappings[:] = []

session.bulk_update_mappings(Bar, mappings)

This will make sure you don't have too much data hanging in memory and you don't do a too big insert to the DB at a single time