[sqlalchemy] Re: one to many relation, removing and adding list issue
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed instance
again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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[sqlalchemy] Re: TypeDecorator Problem with basic association pattern
Hi Michael, yes, you're right of course. This overlapped with the other issue you mentioned about the nutrient_weight/weight column name. I didn't realize this at once. When I change the column name or the mapping appropriately I don't need to return None anymore. Thanks again Frank -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] .info dict on Column
On Tue, Aug 24, 2010 at 02:48:37PM -0400, Michael Bayer wrote:
Info option is clearly very handy. At the moment I implemented an image
field in sqlkit, (that's just a bunch of handler in the gui). In order to do
that I used a type inherited with no addition, just to understand that that
field is the path to an Image:
class Image(String): pass
clearly another alternative would be to use info={ 'image': true} or
similar. Is there some caveat that would make one preferred over the other?
The caveat there is that table reflection, which isn't used in your case,
would produce VARCHAR and not String, or your custom Image type. It also
creates a hard linkage of SQLAlchemy type objects to the behavior of your
application. The info approach allows the type and your application's
interpretation of a field to vary independently.
ok, I switched to using .info and I honestly appreciate it.
am I wrong or Columns created with orm.column_property() don't have .info
attribute? Any chance to add it?
sandro
*:-)
--
Sandro Dentella *:-)
http://sqlkit.argolinux.orgSQLkit home page - PyGTK/python/sqlalchemy
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Re: [sqlalchemy] Re: one to many relation, removing and adding list issue
hi,
The problem seems to be a little bit more general, I have a unique class (doing
nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of the
session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map of
the session
Always the same session, I add again the python instance to the session, flush,
commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
from sqlalchemy import __version__, MetaData, Table, Column, Integer, String,
create_engine, orm #...@unresolvedimport
from sqlalchemy.orm import mapper #...@unresolvedimport
from sqlalchemy.orm import backref #...@unresolvedimport @UnusedImport
print __version__
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
class One(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return self.name
mapper_one = mapper(One,tb_one)
engine = create_engine('postgres://fma:fma6...@localhost:5432/postgres',
convert_unicode=True)
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
o1 = One(One)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.delete(o1)
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed instance
again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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Re: [sqlalchemy] .info dict on Column
On Aug 26, 2010, at 5:09 AM, Alessandro Dentella wrote:
On Tue, Aug 24, 2010 at 02:48:37PM -0400, Michael Bayer wrote:
Info option is clearly very handy. At the moment I implemented an image
field in sqlkit, (that's just a bunch of handler in the gui). In order to do
that I used a type inherited with no addition, just to understand that that
field is the path to an Image:
class Image(String): pass
clearly another alternative would be to use info={ 'image': true} or
similar. Is there some caveat that would make one preferred over the other?
The caveat there is that table reflection, which isn't used in your case,
would produce VARCHAR and not String, or your custom Image type. It also
creates a hard linkage of SQLAlchemy type objects to the behavior of your
application. The info approach allows the type and your application's
interpretation of a field to vary independently.
ok, I switched to using .info and I honestly appreciate it.
am I wrong or Columns created with orm.column_property() don't have .info
attribute? Any chance to add it?
dig in to class.attr.property.columns[0] or class.attr.__clause_element__().
Its probably a good idea for .info to be shared on the class.attr at some
point.
sandro
*:-)
--
Sandro Dentella *:-)
http://sqlkit.argolinux.orgSQLkit home page - PyGTK/python/sqlalchemy
--
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[sqlalchemy] Re: one to many relation, removing and adding list issue
Sorry if you receive this twice, I am not sure if it had been
correctly posted.
On 26 août, 14:49, Martin-Leon Francois francois@gmail.com
wrote:
hi,
The problem seems to be a little bit more general, I have a unique class
(doing nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of the
session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map
of the session
Always the same session, I add again the python instance to the session,
flush, commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
from sqlalchemy import __version__, MetaData, Table, Column, Integer, String,
create_engine, orm #...@unresolvedimport
from sqlalchemy.orm import mapper #...@unresolvedimport
from sqlalchemy.orm import backref #...@unresolvedimport @UnusedImport
print __version__
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
class One(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return self.name
mapper_one = mapper(One,tb_one)
engine = create_engine('postgres://fma:fma6...@localhost:5432/postgres',
convert_unicode=True)
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
o1 = One(One)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.delete(o1)
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed
instance again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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Re: [sqlalchemy] Re: one to many relation, removing and adding list issue
On Aug 26, 2010, at 8:49 AM, Martin-Leon Francois wrote:
hi,
The problem seems to be a little bit more general, I have a unique class
(doing nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of the
session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map
of the session
Always the same session, I add again the python instance to the session,
flush, commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
OK this is a little strange. o1 has been deleted. You've found one
particular operation that doesn't immediately raise (add()), but anything else
you did with o1 would, for example:
print o1.name
you will get this (since o1 is expired and will refresh, then fail):
sqlalchemy.orm.exc.ObjectDeletedError: Instance 'One at 0x1288c70'
has been deleted.
as you've already figured out, o1 has state on it that tells SQLAlchemy that
this object is already persistent - no INSERT will be executed again for the
object. The strange part here is that the object is beyond persistent and is
in the deleted state, and we don't have an in-memory flag that would signal
this, though perhaps that is called for here, I've never seen anyone trying to
perform such an operation before.
Anyway to convert from persistent back to transient, use make_transient:
from sqlalchemy.orm import make_transient
make_transient(o1)
then the key is removed and the object is as though you just created it.
I want to check if there's some foolproof way we can block on add().
Also, the add()/add_all() calls are redundant as is the flush() right before
the commit().
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed
instance again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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[sqlalchemy] hot to get connection pool from engine?
Dear All, After I read SQLAlchemy;s FAQ I think below code may works, import sqlalchemy.pool as pool import sqlite3 as sqlite3 conn_proxy = pool.manage(sqlite3) # then connect normally connection = conn_proxy.connect(...) however I also get below snippets: engine = create_engine(...) conn = engine.connect() conn.connection.do DBAPI things cursor = conn.connection.cursor(DBAPI specific arguments..) then my question is how to get pool from engine? I means can I do something like this? conn_proxy = engine.pool.manage(sqlite3) or conn_pool = engine.pool and is there a way can commit every connection in a connection pool? Thanks! Rgs, KC -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Re: one to many relation, removing and adding list issue
ok, many thx
fma
Le 26 août 2010 à 17:03, Michael Bayer a écrit :
On Aug 26, 2010, at 8:49 AM, Martin-Leon Francois wrote:
hi,
The problem seems to be a little bit more general, I have a unique class
(doing nothing) mapped to a unique table.
After opening a session, I create an instance, add it to the session, flush,
commit.
Everything is ok. -- a row in the table, instance in the identity_map of
the session
Always in the same session, I delete the instance from the session., flush,
commit.
Everything is ok. -- no row in the table, no instance in the identity_map
of the session
Always the same session, I add again the python instance to the session,
flush, commit.
??? -- no row in the table, instance in the identity_map of the session
Could you have a look to the code below and help me figure out what I doing
wrong?
fma
#If I uncomment the following line (workaround) instance is written down to
#the database as I would expect
#o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
s.add(o1)
s.add_all([o1])
s.flush()
s.commit()
print list(s.query(One)), s.identity_map
s.close()
OK this is a little strange. o1 has been deleted. You've found one
particular operation that doesn't immediately raise (add()), but anything
else you did with o1 would, for example:
print o1.name
you will get this (since o1 is expired and will refresh, then fail):
sqlalchemy.orm.exc.ObjectDeletedError: Instance 'One at 0x1288c70'
has been deleted.
as you've already figured out, o1 has state on it that tells SQLAlchemy that
this object is already persistent - no INSERT will be executed again for the
object. The strange part here is that the object is beyond persistent and
is in the deleted state, and we don't have an in-memory flag that would
signal this, though perhaps that is called for here, I've never seen anyone
trying to perform such an operation before.
Anyway to convert from persistent back to transient, use make_transient:
from sqlalchemy.orm import make_transient
make_transient(o1)
then the key is removed and the object is as though you just created it.
I want to check if there's some foolproof way we can block on add().
Also, the add()/add_all() calls are redundant as is the flush() right before
the commit().
Le 26 août 2010 à 08:42, fma a écrit :
Any suggestion helping solving this?
On 25 août, 13:02, Martin-Leon Francois francois@gmail.com
wrote:
Hi,
I am trying in the same session to detach an instance from a collection (
one to many)
flush and commit everything (all is ok) and then attach the removed
instance again. unsuccessfully.
in below code, last assert fails.
I don't understand why I am not able to append m2 to o1.to_many collection
once removed.
Any idea? ( I use sa 0.5.6)
thanx, Francois
meta = MetaData()
tb_one = Table(one, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True))
tb_many = Table(many, meta,
Column('name',String(50)),
Column('id',Integer, primary_key=True),
Column('one_id', Integer,
ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
class One(object):
def __init__(self, name):
self.name = name
class Many(object):
def __init__(self, name):
self.name = name
mapper_one = mapper(One,tb_one)
mapper_many = mapper(Many, tb_many,
properties = dict(
to_one = relation(One,uselist=False,
backref=backref('to_many', cascade=save-update, merge, delete,
delete-orphan),)))
engine = create_engine()
Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
meta.bind = engine
meta.drop_all(checkfirst=True)
meta.create_all(checkfirst=True)
s = Session()
m1 = Many(M1)
m2 = Many(M2)
o1 = One(One)
o1.to_many.append(m1)
o1.to_many.append(m2)
s.add_all([m1,m2,o1])
s.flush()
s.commit()
assert(len(o1.to_many) == 2)
o1.to_many.remove(m2)
assert(len(o1.to_many) == 1)
s.flush()
s.commit()
assert(len(o1.to_many) == 1)
o1.to_many.append(m2)
assert(len(o1.to_many) == 2)
s.flush()
s.commit()
assert(len(o1.to_many) == 2) #this assert fails why?
s.close()
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Re: [sqlalchemy] one to many relation, removing and adding list issue
On Aug 25, 2010, at 7:02 AM, Martin-Leon Francois wrote: assert(len(o1.to_many) == 2) #this assert fails why? OK so as of r2e09679be06b, your original test now returns: sqlalchemy.exc.InvalidRequestError: Instance 'Many at 0x12922f0' has been deleted. Use the make_transient() function to send this object back to the transient state. so that it's clear what's going on. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] reflected column spec doesn't match model column spec
Hi All,
For the following model:
class Header(Base):
__tablename__ = 'header'
id = Column(Integer, primary_key=True)
message_id = Column(Integer,ForeignKey('message.id'))
name = Column(String(50))
value = Column(Text(255))
sqlalchemy-migrate's SchemaDiff tool against the table freshly created
in MySQL gives:
Schema diffs:
tables with differences: header
header with different declaration of columns in database:
[(Column('value', Text(length=255, convert_unicode=False,
assert_unicode=None, unicode_error=None, _warn_on_bytestring=False),
table=header), Column(u'value', TINYTEXT(), table=header), 'value
TEXT(255)', 'value TINYTEXT')]
The schema diff stuff basically does the following to get the database
column declaration with SA 0.6+:
from sqlalchemy.ext import compiler
from sqlalchemy.schema import DDLElement
class DefineColumn(DDLElement):
def __init__(self, col):
self.col = col
@compiler.compiles(DefineColumn)
def compile(elem, compiler, **kw):
return compiler.get_column_specification(elem.col)
def get_column_specification(col):
return str(DefineColumn(col).compile(dialect=self.conn.dialect))
How can it be changed so that the column reflected from the DB and the
column calculated from the model end up being the same?
cheers,
Chris
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[sqlalchemy] how to get connection pool from engine?
Sorry for last mail, I clicked send without spell check, so it may cause confuse, pls ignore last mail. = Dear All, After I read SQLAlchemy's FAQ I think below code may works, import sqlalchemy.pool as pool import sqlite3 as sqlite3 conn_proxy = pool.manage(sqlite3) # then connect normally connection = conn_proxy.connect(...) however I also get below snippets: engine = create_engine(...) conn = engine.connect() conn.connection.do DBAPI things cursor = conn.connection.cursor(DBAPI specific arguments..) then my question is how to get pool from engine? I means can I do something like this? conn_proxy = engine.pool.manage(sqlite3) or conn_pool = engine.pool and is there a way can commit every connection in a connection pool? Thanks! Rgs, -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] reflected column spec doesn't match model column spec
On Aug 26, 2010, at 11:42 AM, Chris Withers wrote:
Hi All,
For the following model:
class Header(Base):
__tablename__ = 'header'
id = Column(Integer, primary_key=True)
message_id = Column(Integer,ForeignKey('message.id'))
name = Column(String(50))
value = Column(Text(255))
sqlalchemy-migrate's SchemaDiff tool against the table freshly created in
MySQL gives:
Schema diffs:
tables with differences: header
header with different declaration of columns in database:
[(Column('value', Text(length=255, convert_unicode=False,
assert_unicode=None, unicode_error=None, _warn_on_bytestring=False),
table=header), Column(u'value', TINYTEXT(), table=header), 'value
TEXT(255)', 'value TINYTEXT')]
The schema diff stuff basically does the following to get the database column
declaration with SA 0.6+:
from sqlalchemy.ext import compiler
from sqlalchemy.schema import DDLElement
class DefineColumn(DDLElement):
def __init__(self, col):
self.col = col
@compiler.compiles(DefineColumn)
def compile(elem, compiler, **kw):
return compiler.get_column_specification(elem.col)
def get_column_specification(col):
return str(DefineColumn(col).compile(dialect=self.conn.dialect))
How can it be changed so that the column reflected from the DB and the column
calculated from the model end up being the same?
if schemas are being diffed, types can be compared generically using type
affinity. This is described at:
http://www.sqlalchemy.org/trac/wiki/06Migration#ReflectionReturnsDialect-SpecificTypes
You could also take a reflected table and force all of its types down to the
generic ones using a hack like column.type.__class__ =
column.type._type_affinity to change the class of each type down to its basic
version. But if a diff is all that's needed they should be using that.
(FYI alembic will have no schema diff feature its not something I buy into much)
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[sqlalchemy] CircularDependencyError on 0.6 (works on 0.5.8)
Hi again, sorry for flooding with email this week...
I stumbled on the CircularDependencyError in some occasions with self
referencing models. I do understand that it can be tricky to INSERT and DELETE
but I'm just updating rows.
I reduced my problem to the bare minimum. It works both on 0.5.8 and 0.6.3
in the test case, but as long as I use the same objects from a graphical GUI
I get an error, Debugging with pdb, the problem arises on session.begin()
and in that moment the situation seems to me exactly the one of the test (2
objects, one modified).
I hope the error message is meaningful to you...
So the situation:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Table, Column, ForeignKey
from sqlalchemy.types import *
from sqlalchemy import orm, sql
Base = declarative_base()
URL = 'postgresql://localhost/scuole'
Base.metadata.bind = URL
Session = orm.sessionmaker()
sess = Session(bind=Base.metadata.bind, expire_on_commit=False,
autoflush=False, autocommit=True, )
class School(Base):
__tablename__ = 'scuola_scuola'
cod = Column(String(10), primary_key=True)
denominazione= Column(String(120))
cod_riferimento = Column(String(10), ForeignKey(cod))
cliente = Column(Boolean, nullable=False)
sedi = orm.relation('School', )
def __repr__(self):
return self.cod
Base.metadata.create_all()
# s1 = School(cod=S1, cod_riferimento=S1, cliente=False)
# d1 = School(cod=D1, cod_riferimento=S1, cliente=False)
# sess.add(s1)
# sess.add(d1)
# sess.commit()
s1 = sess.query(School).get('S1')
d1 = sess.query(School).get('D1')
d1.cliente = False
sess.begin()
sess.commit()
This same peace of code (i.e.: same session with just s1, d1), run from
within a GUI raises an error (only with SA 0.6.3, 0.5.8 just works). The
error is:
Traceback (most recent call last):
File /misc/src/hg/py/sqlkit/sqlkit/widgets/mask/mask.py, line 388, in
record_save_cb
self.record_save(None)
File /misc/src/hg/py/sqlkit/sqlkit/widgets/mask/mask.py, line 422, in
record_save
self.commit()
File /misc/src/hg/py/sqlkit/sqlkit/widgets/common/sqlwidget.py, line 972,
in commit
self.session.begin()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
598, in begin
self, nested=nested)
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
223, in __init__
self._take_snapshot()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
271, in _take_snapshot
self.session.flush()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
1346, in flush
self._flush(objects)
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
1427, in _flush
flush_context.execute()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/unitofwork.py, line
291, in execute
postsort_actions):
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/topological.py, line
31, in sort_as_subsets
(find_cycles(tuples, allitems), _dump_edges(edges, True)))
sqlalchemy.exc.CircularDependencyError: Circular dependency detected:
cycles: set([SaveUpdateState(School at 0x8da616c),
ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False)]) all edges: [(SaveUpdateState(School at 0x8da616c),
ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False)), (ProcessState(OneToManyDP(School.sedi), School at
0x8da616c, delete=False), SaveUpdateState(School at 0x8da616c)),
(SaveUpdateState(School at 0x8da616c), SaveUpdateState(School at
0x8da616c)), (SaveUpdateState(School at 0x8da616c),
SaveUpdateState(School at 0x8da61ec)),
(ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False), SaveUpdateState(School at 0x8da61ec))]
How can I further investigate what Is wrong from the setup of my GUI?
Thanks again
sandro
*:-)
--
Sandro Dentella *:-)
http://sqlkit.argolinux.orgSQLkit home page - PyGTK/python/sqlalchemy
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Re: [sqlalchemy] reflected column spec doesn't match model column spec
Michael Bayer wrote: How can it be changed so that the column reflected from the DB and the column calculated from the model end up being the same? if schemas are being diffed, types can be compared generically using type affinity. This is described at: http://www.sqlalchemy.org/trac/wiki/06Migration#ReflectionReturnsDialect-SpecificTypes You could also take a reflected table and force all of its types down to the generic ones using a hack like column.type.__class__ = column.type._type_affinity to change the class of each type down to its basic version. But if a diff is all that's needed they should be using that. Cool, I shall have a look into that, thanks! (FYI alembic will have no schema diff feature its not something I buy into much) Unfortunately, I'm in an environment where people are accident prone / lazy. Numbers in a version table do not imply the schema actually matches the model ;-) Schema diffing is the only way I can see to be safe. How's Alembic progressing? Some of the stuff in Migrate (like the monkey patching of new bases classes into things like Table and Column) makes my skin crawl, but I didn't see any checkins to Alembic in the last few months... Chris -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] CircularDependencyError on 0.6 (works on 0.5.8)
need a full test case. Here's yours, runs fine:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import *
from sqlalchemy.types import *
from sqlalchemy.orm import *
Base = declarative_base()
e = create_engine('sqlite://', echo=True)
Base.metadata.bind = e
sess = sessionmaker(e)()
class School(Base):
__tablename__ = 'scuola_scuola'
cod = Column(String(10), primary_key=True)
denominazione= Column(String(120))
cod_riferimento = Column(String(10), ForeignKey(cod))
cliente = Column(Boolean, nullable=False)
sedi = relation('School', )
def __repr__(self):
return self.cod
Base.metadata.create_all()
s1 = School(cod=S1, cod_riferimento=S1, cliente=False)
d1 = School(cod=D1, cod_riferimento=S1, cliente=False)
sess.add(s1)
sess.add(d1)
sess.commit()
s1 = sess.query(School).get('S1')
d1 = sess.query(School).get('D1')
d1.cliente = False
sess.commit()
On Aug 26, 2010, at 12:12 PM, Alessandro Dentella wrote:
Hi again, sorry for flooding with email this week...
I stumbled on the CircularDependencyError in some occasions with self
referencing models. I do understand that it can be tricky to INSERT and DELETE
but I'm just updating rows.
I reduced my problem to the bare minimum. It works both on 0.5.8 and 0.6.3
in the test case, but as long as I use the same objects from a graphical GUI
I get an error, Debugging with pdb, the problem arises on session.begin()
and in that moment the situation seems to me exactly the one of the test (2
objects, one modified).
I hope the error message is meaningful to you...
So the situation:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Table, Column, ForeignKey
from sqlalchemy.types import *
from sqlalchemy import orm, sql
Base = declarative_base()
URL = 'postgresql://localhost/scuole'
Base.metadata.bind = URL
Session = orm.sessionmaker()
sess = Session(bind=Base.metadata.bind, expire_on_commit=False,
autoflush=False, autocommit=True, )
class School(Base):
__tablename__ = 'scuola_scuola'
cod = Column(String(10), primary_key=True)
denominazione= Column(String(120))
cod_riferimento = Column(String(10), ForeignKey(cod))
cliente = Column(Boolean, nullable=False)
sedi = orm.relation('School', )
def __repr__(self):
return self.cod
Base.metadata.create_all()
# s1 = School(cod=S1, cod_riferimento=S1, cliente=False)
# d1 = School(cod=D1, cod_riferimento=S1, cliente=False)
# sess.add(s1)
# sess.add(d1)
# sess.commit()
s1 = sess.query(School).get('S1')
d1 = sess.query(School).get('D1')
d1.cliente = False
sess.begin()
sess.commit()
This same peace of code (i.e.: same session with just s1, d1), run from
within a GUI raises an error (only with SA 0.6.3, 0.5.8 just works). The
error is:
Traceback (most recent call last):
File /misc/src/hg/py/sqlkit/sqlkit/widgets/mask/mask.py, line 388, in
record_save_cb
self.record_save(None)
File /misc/src/hg/py/sqlkit/sqlkit/widgets/mask/mask.py, line 422, in
record_save
self.commit()
File /misc/src/hg/py/sqlkit/sqlkit/widgets/common/sqlwidget.py, line 972,
in commit
self.session.begin()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
598, in begin
self, nested=nested)
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
223, in __init__
self._take_snapshot()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
271, in _take_snapshot
self.session.flush()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
1346, in flush
self._flush(objects)
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
1427, in _flush
flush_context.execute()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/unitofwork.py,
line 291, in execute
postsort_actions):
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/topological.py, line
31, in sort_as_subsets
(find_cycles(tuples, allitems), _dump_edges(edges, True)))
sqlalchemy.exc.CircularDependencyError: Circular dependency detected:
cycles: set([SaveUpdateState(School at 0x8da616c),
ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False)]) all edges: [(SaveUpdateState(School at 0x8da616c),
ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False)), (ProcessState(OneToManyDP(School.sedi), School at
0x8da616c, delete=False), SaveUpdateState(School at 0x8da616c)),
(SaveUpdateState(School at 0x8da616c), SaveUpdateState(School at
0x8da616c)), (SaveUpdateState(School at 0x8da616c),
SaveUpdateState(School at 0x8da61ec)),
(ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False), SaveUpdateState(School at 0x8da61ec))]
How can I further investigate what Is wrong from the setup of my GUI?
Thanks
Re: [sqlalchemy] CircularDependencyError on 0.6 (works on 0.5.8)
of course you'll get a cycle if you do this, though:
s1 = School(cod=S1, cod_riferimento=S1, cliente=False)
d1 = School(cod=D1, cod_riferimento=S1, cliente=False)
s1.sedi = [s1, d1]
s1-s1 is not supported by self referential flushes, unless you put
post_update=True on the relation() you have there.
On Aug 26, 2010, at 12:30 PM, Michael Bayer wrote:
need a full test case. Here's yours, runs fine:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import *
from sqlalchemy.types import *
from sqlalchemy.orm import *
Base = declarative_base()
e = create_engine('sqlite://', echo=True)
Base.metadata.bind = e
sess = sessionmaker(e)()
class School(Base):
__tablename__ = 'scuola_scuola'
cod = Column(String(10), primary_key=True)
denominazione= Column(String(120))
cod_riferimento = Column(String(10), ForeignKey(cod))
cliente = Column(Boolean, nullable=False)
sedi = relation('School', )
def __repr__(self):
return self.cod
Base.metadata.create_all()
s1 = School(cod=S1, cod_riferimento=S1, cliente=False)
d1 = School(cod=D1, cod_riferimento=S1, cliente=False)
sess.add(s1)
sess.add(d1)
sess.commit()
s1 = sess.query(School).get('S1')
d1 = sess.query(School).get('D1')
d1.cliente = False
sess.commit()
On Aug 26, 2010, at 12:12 PM, Alessandro Dentella wrote:
Hi again, sorry for flooding with email this week...
I stumbled on the CircularDependencyError in some occasions with self
referencing models. I do understand that it can be tricky to INSERT and
DELETE
but I'm just updating rows.
I reduced my problem to the bare minimum. It works both on 0.5.8 and 0.6.3
in the test case, but as long as I use the same objects from a graphical GUI
I get an error, Debugging with pdb, the problem arises on session.begin()
and in that moment the situation seems to me exactly the one of the test (2
objects, one modified).
I hope the error message is meaningful to you...
So the situation:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Table, Column, ForeignKey
from sqlalchemy.types import *
from sqlalchemy import orm, sql
Base = declarative_base()
URL = 'postgresql://localhost/scuole'
Base.metadata.bind = URL
Session = orm.sessionmaker()
sess = Session(bind=Base.metadata.bind, expire_on_commit=False,
autoflush=False, autocommit=True, )
class School(Base):
__tablename__ = 'scuola_scuola'
cod = Column(String(10), primary_key=True)
denominazione= Column(String(120))
cod_riferimento = Column(String(10), ForeignKey(cod))
cliente = Column(Boolean, nullable=False)
sedi = orm.relation('School', )
def __repr__(self):
return self.cod
Base.metadata.create_all()
# s1 = School(cod=S1, cod_riferimento=S1, cliente=False)
# d1 = School(cod=D1, cod_riferimento=S1, cliente=False)
# sess.add(s1)
# sess.add(d1)
# sess.commit()
s1 = sess.query(School).get('S1')
d1 = sess.query(School).get('D1')
d1.cliente = False
sess.begin()
sess.commit()
This same peace of code (i.e.: same session with just s1, d1), run from
within a GUI raises an error (only with SA 0.6.3, 0.5.8 just works). The
error is:
Traceback (most recent call last):
File /misc/src/hg/py/sqlkit/sqlkit/widgets/mask/mask.py, line 388, in
record_save_cb
self.record_save(None)
File /misc/src/hg/py/sqlkit/sqlkit/widgets/mask/mask.py, line 422, in
record_save
self.commit()
File /misc/src/hg/py/sqlkit/sqlkit/widgets/common/sqlwidget.py, line 972,
in commit
self.session.begin()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
598, in begin
self, nested=nested)
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
223, in __init__
self._take_snapshot()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
271, in _take_snapshot
self.session.flush()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
1346, in flush
self._flush(objects)
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/session.py, line
1427, in _flush
flush_context.execute()
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/orm/unitofwork.py,
line 291, in execute
postsort_actions):
File /misc/src/sqlalchemy/sqlalchemy/lib/sqlalchemy/topological.py, line
31, in sort_as_subsets
(find_cycles(tuples, allitems), _dump_edges(edges, True)))
sqlalchemy.exc.CircularDependencyError: Circular dependency detected:
cycles: set([SaveUpdateState(School at 0x8da616c),
ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False)]) all edges: [(SaveUpdateState(School at 0x8da616c),
ProcessState(OneToManyDP(School.sedi), School at 0x8da616c,
delete=False)), (ProcessState(OneToManyDP(School.sedi), School at
0x8da616c, delete=False), SaveUpdateState(School at 0x8da616c)),
(SaveUpdateState(School at
Re: [sqlalchemy] reflected column spec doesn't match model column spec
On Aug 26, 2010, at 12:15 PM, Chris Withers wrote: Michael Bayer wrote: How can it be changed so that the column reflected from the DB and the column calculated from the model end up being the same? if schemas are being diffed, types can be compared generically using type affinity. This is described at: http://www.sqlalchemy.org/trac/wiki/06Migration#ReflectionReturnsDialect-SpecificTypes You could also take a reflected table and force all of its types down to the generic ones using a hack like column.type.__class__ = column.type._type_affinity to change the class of each type down to its basic version. But if a diff is all that's needed they should be using that. Cool, I shall have a look into that, thanks! (FYI alembic will have no schema diff feature its not something I buy into much) Unfortunately, I'm in an environment where people are accident prone / lazy. Numbers in a version table do not imply the schema actually matches the model ;-) then you have an organizational issue, not a software one. If you're using migrations, people shouldn't be touching the database directly.Databases have great, granular security models to ensure that only one user can actually ALTER anything. Schema diffing is the only way I can see to be safe. DB permissions How's Alembic progressing? Some of the stuff in Migrate (like the monkey patching of new bases classes into things like Table and Column) makes my skin crawl, but I didn't see any checkins to Alembic in the last few months... ive got no time to work on it and no need for it at the moment. There are two major 0.7 features that are higher on my radar as well as some major doc rewrites. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] Change echo at will
Is there a way to set 'echo' at any time? Everything I can find sets it when the engine is created and doesn't seem to change it afterward. Thanks, Michael -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] Re: problem with relationships with a postgres schema using declarative mapping
I think where I'm getting bogged down with the case I have (most
likely because I'm new to relational mapping of db tables anyway) is
how I get data into the intermediate table. What I'm doing here is
setting up a dependency graph where that entityConnections table
needs to have data explicitly added to it without necessarily having
the relational objects for the entity table around. Its
relationship with the Entity object is simply to ask what the
upstream and downstream dependencies are. Maybe the association
object pattern is the way to go with it.
thanks,
nigel
On Aug 25, 6:12 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Aug 25, 2010, at 7:43 PM, Nigel wrote:
Thanks very much for the quick reply. The second suggested worked
nicely. I guess this explains why I was having such a hard time
tracking down a similar situation online!
Maybe I can sneak a second question in here which is to ask why the
many - many connection table can not be created using the declarative
method? Would it be normal to create the mapping for that table after
it has been created in order to get a relational object?
A declarative mapping defines a Table, a user-defined class, and a mapper
associating the two all at once. In the case of secondary, that is a Table
that is referenced by a relationship() as an intermediary table to satisfy
the linkage between two mappers, but is not mapped itself, has no
corresponding user defined class, and is not subject to the same persistence
methods as that of mapped classes.
There is another pattern called the association object pattern, which
removes the secondary argument and explicitly maps the intermediary table,
and then specifies a relationship() from parent to intermediary class, then
another from intermediary to child class. This is a very common pattern and
is used when additional meaningful information is present on the intermediary
table, and there is also a helper called the associationproxy which can
allow such a configuration to act like a many-to-many when that's all that's
needed.
Both patterns can also be combined. Doing so is not really necessary as the
associationproxy is a cleaner solution, but the secondary method offers a
slight performance gain when loading related rows. If the two patterns are
combined, you'd usually want to add viewonly=True to the relationship()
that references the Table via secondary. If this is not done, a mutation
to the secondary relationship that is mirrored by mutations to the
association relationship can cause conflicting instructions during a flush.
Thanks again,
nigel
On Aug 25, 4:20 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Aug 25, 2010, at 4:57 PM, Nigel wrote:
Hi all,
I'm having some trouble with using a schema with a many-to-many
declarative mapping. The error i'm getting is as follows:
sqlalchemy.exc.InvalidRequestError: One or more mappers failed to
compile. Exception was probably suppressed within a hasattr() call.
Message was: One or more mappers failed to compile. Exception was
probably suppressed within a hasattr() call. Message was: When
compiling mapper Mapper|Entity|entity, expression 'Entity.id ==
entityConnections.c.masterId' failed to locate a name (name
'entityConnections' is not defined). If this is a class name,
consider adding this relationship() to the class '__main__.Entity'
class after both dependent classes have been defined.
Here is a bit of code that will fail. Please excuse the word wrapping:
Base = declarative_base( bind = engine )
entityConnection = Table( 'entityConnections', Base.metadata,
Column( 'masterId', Integer,
ForeignKey( 'relationalSchema.entity.id' ), primary_key = True ),
Column( 'slaveId', Integer,
ForeignKey( 'relationalSchema.entity.id' ), primary_key = True ),
schema = 'relationalSchema' )
class Entity( Base ):
__tablename__ = 'entity'
__table_args__ = { 'schema':'relationalSchema' }
id = Column( Integer, primary_key = True )
entityType = Column(String)
connections = relationship( 'Entity', secondary = entityConnection,
primaryjoin = Entity.id == entityConnections.c.masterId,
secondaryjoin = Entity.id == entityConnections.c.slaveId,backref =
'entity' )
def __init__(self, entityType ):
self.entityType = entityType
def __repr__(self):
return Entity('%s') % ( self.entityType )
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind=engine)
session = Session()
session.add( Entity( 'test' ) )
If I remove the references to the schema the code runs fine. Adding
the schema to the primaryjoin and secondaryjoin just changes the error
so it must be something else. Any ideas what I'm doing wrong here?
I'm a rank newbie with sqlalchemy so it's probably a pretty easy thing
to fix!
er OK you're actually doing something that has not
Re: [sqlalchemy] Change echo at will
On Thu, Aug 26, 2010 at 4:21 PM, Michael Hipp mich...@hipp.com wrote: Is there a way to set 'echo' at any time? Everything I can find sets it when the engine is created and doesn't seem to change it afterward. Thanks, Michael You can assign the engine.echo property to True or False any time after creating the engine. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] how to do housekeeping jobs before using sqlalchemy and coworking with python sqlite3 and sqlalchemy ?
On Wed, Aug 25, 2010 at 1:30 PM, keekychen.shared
keekychen.sha...@gmail.com wrote:
How to test if an existing database file is a valid sqlite3 format
file before using sqlalchemy?
Here is function we use
import os, os.path as osp
try:
from pysqlite2 import dbapi2 as sqlite
except:
import sqlite3 as sqlite
def isSQLite(filename):
True if filename is a SQLite database
File is database if: (1) file exists, (2) length is non-zero,
(3) can connect, (4) has sqlite_master table
# validate file exists
if not osp.isfile(filename):
return False
# is not an empty file
if not os.stat(filename).st_size:
return False
# can open a connection
try:
conn = sqlite.connect(filename)
except:
return False
# has sqlite_master
try:
result = conn.execute('pragma table_info(sqlite_master)').fetchall()
if len(result) == 0:
conn.close()
return False
except:
conn.close()
return False
# looks like a good database
conn.close()
return True
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[sqlalchemy] self referencing column
I've been looking through the documentation and I could have sworn I
saw it before but It seem I can't find it once more...
I'm looking for how to set up a self referencing column like in this
pseudo scenerio:
class Action(DeclarativeBase):
__tablename__ = 'action'
id = Column(Integer, autoincrement=True, primary_key=True)
onsuccess = Column(Integer, ForeignKey=('action.id')
I would want to have an id of an action upon the success of an
action...
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[sqlalchemy] Re: self referencing column
I'm guessing that the answer would be as at:
http://www.sqlalchemy.org/trac/wiki/UsageRecipes/DeclarativeSelfReferencingTable
?
On Aug 26, 8:02 pm, waugust waugustyn...@gmail.com wrote:
I've been looking through the documentation and I could have sworn I
saw it before but It seem I can't find it once more...
I'm looking for how to set up a self referencing column like in this
pseudo scenerio:
class Action(DeclarativeBase):
__tablename__ = 'action'
id = Column(Integer, autoincrement=True, primary_key=True)
onsuccess = Column(Integer, ForeignKey=('action.id')
I would want to have an id of an action upon the success of an
action...
--
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Re: [sqlalchemy] Re: self referencing column
This is the documentation for self referential mapper:
http://www.sqlalchemy.org/docs/mappers.html#adjacency-list-relationships
I guess you have found the recipes for doing it the declarative way.
2010/8/26 waugust waugustyn...@gmail.com:
I'm guessing that the answer would be as at:
http://www.sqlalchemy.org/trac/wiki/UsageRecipes/DeclarativeSelfReferencingTable
?
On Aug 26, 8:02 pm, waugust waugustyn...@gmail.com wrote:
I've been looking through the documentation and I could have sworn I
saw it before but It seem I can't find it once more...
I'm looking for how to set up a self referencing column like in this
pseudo scenerio:
class Action(DeclarativeBase):
__tablename__ = 'action'
id = Column(Integer, autoincrement=True, primary_key=True)
onsuccess = Column(Integer, ForeignKey=('action.id')
I would want to have an id of an action upon the success of an
action...
--
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--
Alex
twitter.com/alexconrad
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Re: [sqlalchemy] Re: self referencing column
Thanks, though! :)
Don't suppose you would have an idea on how I could store a procedure? :)
the actions to which I'm pertaining I envisioned as controller actions
(Pylons) that I could define an associate with an execution flow... (don't
know if that makes sense)...
I was thinking of just storing the Route url and execute it with app.get or
app.post though idk...
On Thu, Aug 26, 2010 at 10:21 PM, Alexandre Conrad
alexandre.con...@gmail.com wrote:
This is the documentation for self referential mapper:
http://www.sqlalchemy.org/docs/mappers.html#adjacency-list-relationships
I guess you have found the recipes for doing it the declarative way.
2010/8/26 waugust waugustyn...@gmail.com:
I'm guessing that the answer would be as at:
http://www.sqlalchemy.org/trac/wiki/UsageRecipes/DeclarativeSelfReferencingTable
?
On Aug 26, 8:02 pm, waugust waugustyn...@gmail.com wrote:
I've been looking through the documentation and I could have sworn I
saw it before but It seem I can't find it once more...
I'm looking for how to set up a self referencing column like in this
pseudo scenerio:
class Action(DeclarativeBase):
__tablename__ = 'action'
id = Column(Integer, autoincrement=True, primary_key=True)
onsuccess = Column(Integer, ForeignKey=('action.id')
I would want to have an id of an action upon the success of an
action...
--
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Alex
twitter.com/alexconrad
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