Re: [sqlalchemy] Re: insert defaults
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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Re: [sqlalchemy] Re: insert defaults
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 =
Re: [sqlalchemy] Re: insert defaults
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 is
http://www.sqlalchemy.org/docs/session.html#embedding-sql-insert-update-expressions-into-a-flush
.
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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