Hi all,
I have a PG database with tables like the following
Column | Type | Modifiers
---------+-----------------------------+------------------------------------------
id | uuid | not null default uuid_generate_v1()
created | timestamp without time zone | not null default
transaction_timestamp()
changed | timestamp without time zone |
name | character varying(192) | not null
code | character varying(64) | not null
value | integer |
with a trigger that updates the "changed" field whenever a record is modified.
Accordingly to the documentation[1] I thus modelled it like in the following
way:
import sqlalchemy as sa
import sqlalchemy.orm as orm
import sqlalchemy.types as types
import sqlalchemy.dialects.postgresql as sapg
md = sa.MetaData()
testtable = sa.Table(
'testtable', md,
sa.Column('id', sapg.UUID(True),
primary_key=True,
nullable=False,
server_default=sa.func.uuid_generate_v1()),
sa.Column('created', types.DateTime(),
nullable=False,
server_default=sa.func.transaction_timestamp()),
sa.Column('changed', types.DateTime(),
server_onupdate=sa.FetchedValue()),
sa.Column('name', types.Unicode(192),
nullable=False),
sa.Column('code', types.Unicode(64),
nullable=False),
sa.Column('value', types.Integer,
nullable=True))
class Base:
def __init__(self, **kwargs):
cls_ = type(self)
for k in kwargs:
setattr(self, k, kwargs[k])
class TestTable(Base):
pass
orm.mapper(TestTable, testtable)
This works, but I notice that SA explicitly inserts the "changed" field with a
None value on INSERTs, that is the following snippet:
e = sa.create_engine('postgresql://localhost/test', echo=True)
md.create_all(e)
s = orm.Session(e)
o1 = TestTable(name='foo', code='bar')
s.add(o1)
s.commit()
produces a log like the following:
2018-02-04 11:34:12,464 INFO sqlalchemy.engine.base.Engine INSERT INTO
testtable (changed, name, code, value) VALUES (%(changed)s, %(name)s, %(code)s,
%(value)s) RETURNING testtable.id
2018-02-04 11:34:12,464 INFO sqlalchemy.engine.base.Engine {'changed':
None, 'name': 'foo', 'code': 'bar', 'value': None}
The doubt is: why is SA providing explicit None values for both "changed" and
"value" fields? Am I missing something in the table description or what?
Thanks in advance for any enlightenment!
ciao, lele.
[1] http://docs.sqlalchemy.org/en/latest/core/defaults.html#triggered-columns
--
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
l...@metapensiero.it | -- Fortunato Depero, 1929.
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