Get fails with "writable buffers not hashable" when run in a separate session. #390
Description
Issue #355 is not solved completely, I can still trigger it when the object creation and get are in different sessions, and unique buffer is an optional field.
from pony import orm
from pony.orm import db_session
db = orm.Database()
class Bla(db.Entity):
smt = orm.PrimaryKey(int, auto=True)
opt = orm.Optional(buffer, unique=True)
db.bind(provider='sqlite', filename=':memory:')
db.generate_mapping(create_tables=True)
with db_session:
a = Bla(opt=buffer("123"))
q = orm.select(p for p in Bla)[:]
a_smt = q[0].smt
with db_session:
b = Bla.get(smt=a_smt) File "./pony_bug_buffer.py", line 16, in <module>
b = Bla.get(smt=a_smt)
File "/home/vader/.local/lib/python2.7/site-packages/pony/orm/core.py", line 3768, in get
try: return entity._find_one_(kwargs) # can throw MultipleObjectsFoundError
File "/home/vader/.local/lib/python2.7/site-packages/pony/orm/core.py", line 3867, in _find_one_
if obj is None: obj = entity._find_in_db_(avdict, unique, for_update, nowait)
File "/home/vader/.local/lib/python2.7/site-packages/pony/orm/core.py", line 3927, in _find_in_db_
objects = entity._fetch_objects(cursor, attr_offsets, 1, for_update, avdict)
File "/home/vader/.local/lib/python2.7/site-packages/pony/orm/core.py", line 4059, in _fetch_objects
obj._db_set_(avdict)
File "/home/vader/.local/lib/python2.7/site-packages/pony/orm/core.py", line 4613, in _db_set_
cache.db_update_simple_index(obj, attr, old_val, new_dbval)
File "/home/vader/.local/lib/python2.7/site-packages/pony/orm/core.py", line 1854, in db_update_simple_index
obj2 = cache_index.setdefault(new_dbval, obj)
TypeError: writable buffers are not hashable