I have added support for default column values, which builds upon the
same mechanism that does sequences:
def mydefault():
"""a function that returns a new integer ID"""
return mycounter.increment()
t = Table('default_test1', db,
# set a default function
Column('col1', Integer, primary_key=True, default=mydefault),
# set a literal default
Column('col2', String(20), default="imthedefault"),
# any ClauseElement, which will be pre-executed
Column('col3', Integer, default=func.count(1)),
)
when you do an insert:
t.insert().execute()
you get (positional params shown here), assuming mydefault() returns 27:
SELECT count(?)
[1]
INSERT INTO default_test1 (col1, col2, col3) VALUES (?, ?, ?)
[27, 'imthedefault', 1]
This default functionality applies to all inserts for the table,
whether your making your own inserts or using the mappers.
If you are using mappers, there is also another way to set up default
values on an object when its created, at the object level via
MapperExtension:
class MyExt(MapperExtension):
def before_insert(self, mapper, instance):
instance.main_id = 10
instance.category_id = 17
mapper = mapper(MyClass, mytable, extension=MyExt())
And the "before_insert" method will be called for each new MyClass
instance right before its saved.
MapperExtension actually has a bunch of other hooks too with more on
the way. I still need to write full docs for MapperExtension.
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