On 05/04/2017 08:41 AM, yoch.me...@gmail.com wrote:
Hi,
I'm facing to a strange behavior with bulk update on inherited class.
These two queries work differently :
# raise : Unconsumed column names: name
try:
session.query(Engineer).filter(Engineer.name=='bar').update({'name':'baz'})
session.commit()
exceptExceptionaserr:
print(err)
# with MySQL engine , produce : 'UPDATE engineer, person SET
person.name=%s WHERE person.name = %s'
# with SQLite engine, produce : 'UPDATE engineer SET name=? FROM person
WHERE person.name = ?' [Syntax Error]
try:
session.query(Engineer).filter(Engineer.status=='working').update({'name':'bar'})
session.commit()
exceptExceptionaserr:
print(err)
|
The former query fails, presumably because sqlalchemy don't care with
the parent class.
The later is handled correctly with MySQL (maybe because the fillter
involve Person), but no with SQLite.
(I also tried with_polymorphic, but it doesn't solve the problem).
Is this a bug ?
it's not.
http://docs.sqlalchemy.org/en/latest/orm/query.html?highlight=query%20update#sqlalchemy.orm.query.Query.update
**Warning**
The Query.update() method is a “bulk” operation, which bypasses ORM
unit-of-work automation in favor of greater performance. **Please read
all caveats and warnings below.**
... below ....
* The method supports multiple table updates, as detailed in Multiple
Table Updates, and this behavior does extend to support updates of
joined-inheritance and other multiple table mappings. However, the join
condition of an inheritance mapper is not automatically rendered. Care
must be taken in any multiple-table update to explicitly include the
joining condition between those tables, even in mappings where this is
normally automatic. E.g. if a class Engineer subclasses Employee, an
UPDATE of the Engineer local table using criteria against the Employee
local table might look like:
session.query(Engineer).\
filter(Engineer.id == Employee.id).\
filter(Employee.name == 'dilbert').\
update({"engineer_type": "programmer"})
In your case, your query is only targeting columns in the base "person"
table. So this is not really a multiple table update and instead of
asking it for query(Engineer) you should be asking for
query(Person).filter(Person.type == 'engineer').
Best regards,
yoch
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