patrick wrote:
> Yes, but then my descriptor is washed away. I'm trying to make it
> like a column property on 'get' and a descriptor enabled property on
> 'set'.
here's an example of a full round trip of data going in through a func.()
and out through a func.() - use this recipe:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
engine = create_engine('sqlite://', echo=True)
class Foo(Base):
__tablename__ = 'foo'
id = Column(Integer, primary_key=True)
data = Column(String)
_some_uppercase_thing = column_property(func.lower(data))
def _get_some_uppercase_thing(self):
return self._some_uppercase_thing
def _set_some_uppercase_thing(self, data):
self.data = func.upper(data)
some_uppercase_thing = synonym(
'_some_uppercase_thing',
descriptor=property(
_get_some_uppercase_thing,
_set_some_uppercase_thing
)
)
Base.metadata.create_all(engine)
sess = sessionmaker(engine)()
sess.add_all([
Foo(some_uppercase_thing="value 1"),
Foo(some_uppercase_thing="value 2"),
Foo(some_uppercase_thing="value 3"),
Foo(some_uppercase_thing="value 4"),
])
sess.commit()
assert sess.query(Foo.some_uppercase_thing).all() == [
("value 1", ),
("value 2", ),
("value 3", ),
("value 4", ),
]
assert
sess.query(Foo.some_uppercase_thing).filter(Foo.some_uppercase_thing ==
'value 2').all() == [
("value 2", ),
]
assert sess.execute(select([Foo.__table__.c.data])).fetchall() == [
("VALUE 1", ),
("VALUE 2", ),
("VALUE 3", ),
("VALUE 4", ),
]
>
> On Mar 25, 3:27 pm, "Michael Bayer" <mike...@zzzcomputing.com> wrote:
>> patrick wrote:
>> > In the past I assigned
>> > Matrix.text=column_property(select(["uncompress(compressed)"]),deferred=True)
>> > I could probably write a little SqlSoup to do this select statement,
>> > but is there a way I can integrate this all well? The way I'm doing
>> > this feels very sloppy. SqlAlchemy is powerful, but can be very
>> > complicated.
>>
>> you should map an attribute directly to
>> column_property(uncompress(table.c.compressed)). if you want it only
>> to
>> fire when you read it, use deferred() instead of column_property().
>>
>>
>>
>> > On Mar 5, 8:30 pm, Michael Bayer <mike...@zzzcomputing.com> wrote:
>> >> On Mar 5, 2010, at 6:44 PM, patrick wrote:
>>
>> >> > Well it's something between the two. The instance variable
>> >> > "compressed" will always be NULL when adding or updating an
>> instance,
>> >> > but I want it to infer a value from another instance variable. When
>> >> > inserting... the value of 'compressed' in the sql statement needs
>> to
>> >> > be the raw SQL string "COMPRESS('%s')" % instance.text. It isn't
>> >> > simply running it through a function... it's dynamically creating
>> the
>> >> > column value from the object's instance variables upon insert or
>> >> > update. MySQL has some funky compression function so the insert
>> value
>> >> > for the column has to be raw sql.
>>
>> >> so do a before_insert() mapper extension and set the attribute as
>> needed
>> >> to "func.compressed(instance.text)". Or do the same at the object
>> >> level, i.e user sets myobject.foo, "foo" is a descriptor-enabled
>> method
>> >> which then sets myobject.bar = func.compressed(foo) or whatever.
>>
>> >> the technique here
>> >> ishttp://www.sqlalchemy.org/docs/session.html#embedding-sql-insert-upda....
>>
>> >> > On Mar 4, 3:30 pm, "Michael Bayer" <mike...@zzzcomputing.com>
>> wrote:
>> >> >> patrick wrote:
>> >> >>> Hey,
>> >> >>> I'm trying to create dynamic defaults for columns ala "http://
>> >> >>>www.sqlalchemy.org/docs/metadata.html#context-sensitive-default-funct...".
>> >> >>> MySQL has COMPRESS and UNCOMPRESS functions that I'm trying to
>> >> >>> leverage. I don't want to compress with python's zlib because I
>> >> have
>> >> >>> legacy tables that were compressed using MySQL (which has a weird
>> >> non-
>> >> >>> standard zip header and body), and I need to interface with them.
>> >> >>> Anyway, during an insert or update, I want to grab the 'text'
>> >> variable
>> >> >>> from the instance object and insert it into the database like:
>> >> >>> COMPRESS("the text value"). Obviously context.current_parameters
>> is
>> >> >>> not the appropriate object, but I can't figure out if it's
>> possible
>> >> to
>> >> >>> access the instance being inserted/updated.
>>
>> >> >> are you trying to create a *default* value for an INSERT/UPDATE
>> when
>> >> NULL
>> >> >> would otherwise be passed, or are you trying to run all
>> >> incoming/outgoing
>> >> >> data through a SQL function ? those are two completely separate
>> >> topics.
>>
>> >> >>> def compress_text(context):
>> >> >>> return "COMPRESS('%s')" % context.current_parameters['text']
>>
>> >> >>> class Tree(BaseStruct, Base):
>> >> >>> __tablename__ = 'tree'
>> >> >>> __table_args__ = (
>> >> >>> {'autoload':True}
>> >> >>> )
>>
>> >> >>> compressed =
>> >> >>> deferred(Column(Binary(),default=compress_text,default=compress_text,onupdate=compress_text))
>> >> >>> text =
>> >> >>> column_property(select(["UNCOMPRESS(compressed)"]),deferred=True)
>>
>> >> >>> Is this possible with 0.5.7?
>>
>> >> >>> --
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