Like all CRUD goes, I need to write some data to a table. when I write new
data to the table, everything works like charm. the problem starts when I
need to write data already existing in the table (actually updating some
data with the same primary key).
the data just doesn't seem to be written to the table! I started with
trying to update the data with session.merge(), but later tried a more
brute force approach, of querying for the same primary_key in the table,
deleting it and the adding and flushing the changed objects.
some where, if the basic add and flush failes the rest doesn't work. I'll
be glad for a clue here.
The code:
def flush(obj_Instance, id):
"""
taking care of the sqlalchemy flushing
params:
Instance: an object Instance to flush into
id: the unique object instance id
"""
DBSession2.add(obj_Instance)
try:
try:
DBSession2.flush()
print ("flushed:", str(obj_Instance))
except (FlushError, IntegrityError) as err:
DBSession2.rollback()
if ('conflicts with persistent instance' in str(err)) or
('Duplicate key was ignored' in str(err)):
transaction.begin()
#my original slick take:
DBSession2.merge(obj_instance) # but after it failed to
update correctly I changed to a more brute force approach
#DBSession2.flush() #to save the merge
#from here on trying to brute force it
#saving for further reference - another try
newInstance = deepcopy(obj_Instance)
print ("deleting: %s" % id)
DBSession2.query(type(obj_Instance)).filter_by(ids =
id).delete()
DBSession2.flush() #at this point, I was so desperate for
this to work I literated the code with flush commands.
DBSession2.add(newInstance)
DBSession2.flush()
return
else:
raise #handling the case of the same key problem isn't the
source of conflicts
except Exception as err: # supposed to find out the error type and
message
# the code doesn't get here, only in real exceptions it was planned to
catch, 3 rows in 10,000 uploaded to the db
#TODO: make this less general and more specific
print str(err)
write_log(num=id, msg="some sql or sqlalchemy error use num %s as
id identifier with object: %s" % (id, obj_Instance.name), timestamp=
datetime.now(), errtype="sql error", log=str(err))
DBSession2.rollback()
transaction.begin()
maybe this try/fail/rollback/merge or delete/insert new pattern is wrong
(also I think pythonic - try and ask forgiveness,but that would be for
mike to judge)
using sqlalchemy 0.7.3 vs mssql 2005 with pyodbc 2.1.11 and tg 2.1 (the
transaction manager comes with tg and I think is based transaction)
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