Re: Re: [sqlalchemy] Re: Composite Pattern
OK. I've found the bug. In my UnionCalendar, I called the children,
calendars, which didn't match the name in the mappers.
It works, and here is a one file cut down version
from sqlalchemy import create_engine
from sqlalchemy import Table, Integer, Column, Boolean, String, MetaData,
ForeignKey
from sqlalchemy.orm import mapper, sessionmaker, relationship
class Entity (object):
pass
class Calendar (Entity):
'''
Calendar to contain holiday dates
'''
def __init__ (self, code, name):
self.code = code
self.name = name
def isholiday (self, when):
'''
Is when a holiday in the calendar?
'''
pass
class SimpleCalendar (Calendar):
'''
Calendar with name 'name'
'''
def isholiday (self, when):
return False
def __repr__ (self):
res = %s('%s', %s, %s, %s, %s, %s, %s, %s, '%s')\n % \
(
self.__class__.__name__,
self.code,
self.name
)
return res
class UnionCalendar (Calendar):
'''
A union of more than two calendars
'''
def __init__ (self, cals):
Calendar.__init__(self, .join ([cal.code for cal in cals]), - .join
([cal.name for cal in cals]))
self.children = cals
def isholiday (self, when):
for cal in self.children:
if cal.isholiday (when):
return True
return False
def __repr__ (self):
return UnionCalendar (%s)\n % , .join ([cal.code for cal in
self.children])
engine = create_engine('sqlite:///:memory:', echo=True)
metadata = MetaData()
Session = sessionmaker(bind=engine)
session = Session()
calendars_table = Table \
(
'calendars',
metadata,
Column ('id', Integer, primary_key=True),
Column ('code', String, nullable=False, unique=True),
Column ('name', String),
Column ('calendar_type', String (20), nullable=False)
)
calendar_children_table = Table \
(
'calendar_children',
metadata,
Column ('parent_id', Integer, ForeignKey ('calendars.id')),
Column ('child_id', Integer, ForeignKey ('calendars.id'))
)
calendar_mapper = \
mapper \
(
Calendar,
calendars_table,
polymorphic_on=calendars_table.c.calendar_type,
polymorphic_identity=calendar
)
simple_calendar_mapper = \
mapper \
(
SimpleCalendar,
inherits=calendar_mapper,
polymorphic_identity='simple'
)
union_calendar_mapper = \
mapper \
(
UnionCalendar,
inherits=calendar_mapper,
polymorphic_identity='union',
properties = \
{
'children':relationship \
(
Calendar,
secondary=calendar_children_table,
primaryjoin = calendar_children_table.c.parent_id == calendars_table.c.id,
secondaryjoin = calendar_children_table.c.child_id == calendars_table.c.id
)
}
)
metadata.create_all (engine)
ny = SimpleCalendar(code='NY',name='New York')
lon = SimpleCalendar(code='LON',name='London')
session.add (ny)
session.add (lon)
session.commit()
uc = UnionCalendar ([ny, lon])
print uc
print 'add'
session.add (uc)
session.flush()
session.commit()
print 'done'
for c in uc.children:
print c.code
Thanks for your help Michael.
If you need a generic example for the docs, I'll write it up.
On , Michael Bayer mike...@zzzcomputing.com wrote:
On Mar 31, 2011, at 6:26 AM, Nick Leaton wrote:
OK, still one problem. It's not saving the association object.
Here is the code
===
from sqlalchemy import create_engine
from sqlalchemy import Table, Integer, Column, Boolean, String,
MetaData, ForeignKey
from sqlalchemy.orm import mapper, sessionmaker, relationship
from Entities.Calendar import Calendar
from Entities.SimpleCalendar import SimpleCalendar
from Entities.UnionCalendar import UnionCalendar
from Entities.Holiday import Holiday
from Entities.SimpleHoliday import SimpleHoliday
from Entities.RepeatingHoliday import RepeatingHoliday
ny = SimpleCalendar(code='NY',name='New
York',holidays=[SimpleHoliday(New Year, 2011,1,1)])
lon =
SimpleCalendar(code='LON',name='London',holidays=[SimpleHoliday(New
Year, 2011,1,1),RepeatingHoliday('MayDay',5,1)])
session.add (ny)
session.add (lon)
session.commit()
uc = UnionCalendar ([ny, lon])
print uc
print 'add'
session.add (uc)
session.flush()
So I'd need to see where you are populating children. I don't see that
in the example here (if it is happening, I assume the constructor of
UnionCalendar is doing it somehow) so that would be why nothing gets put
into calendar_children.
if you inline the classes themselves into the test then you'd have an
example others can reproduce.
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For
[sqlalchemy] Composite Pattern
I'm trying to implement a Composite Pattern,
http://en.wikipedia.org/wiki/Composite_pattern
In this case its to represent some holiday calendars. I need to
implement a union calendar that is a collection of other calendars.
So a straightforward hierarchy. Calendar, abstract as the top level
class. SimpleCalendar that inherits from Calendar. Then a union
calendar that inherits from Calendar, but I need to implement
children, a collection of calendars.
So its a self referential hierarchy. The point to note is that one
calendar can appear in more than one union calendar, so its a self
referential many to many. Its certain I need an association table as a
result.
I'm not quite sure how to configure this.
I'm trying something along these lines
calendars_table = Table \
(
'calendars',
metadata,
Column ('id', Integer, primary_key=True),
Column ('code', String, nullable=False, unique=True),
Column ('name', String),
Column ('calendar_type', String (20), nullable=False),
Column ('monday', Boolean),
Column ('tuesday', Boolean),
Column ('wednesday', Boolean),
Column ('thurday', Boolean),
Column ('friday', Boolean),
Column ('saturday', Boolean),
Column ('sunday', Boolean)
)
calendar_children_table = Table \
(
'calendar_children',
metadata,
Column ('parent_id', Integer, ForeignKey ('calendars.id')),
Column ('child_id', Integer, ForeignKey ('calendars.id'))
)
calendar_mapper = mapper (Calendar, calendars_table,
polymorphic_on=calendars_table.c.calendar_type,
polymorphic_identity=calendar)
simple_calendar_mapper = mapper (SimpleCalendar,
inherits=calendar_mapper,
polymorphic_identity='simple',properties={'holidays':relationship(Holiday,
backref='calendar')})
union_calendar_mapper = mapper (UnionCalendar,
inherits=calendar_mapper, polymorphic_identity='union')
holidays_table = Table \
(
'holidays',
metadata,
Column ('id', Integer, primary_key=True),
Column ('holiday_type',String(20), nullable=False),
Column ('calendar_id', Integer, ForeignKey ('calendars.id')),
Column ('description', String ),
Column ('year',Integer),
Column ('month', Integer),
Column ('day', Integer)
)
holiday_mapper = mapper (Holiday, holidays_table,
polymorphic_on=holidays_table.c.holiday_type,
polymorphic_identity='holiday')
repeating_holiday_mapper = mapper (RepeatingHoliday,
inherits=holiday_mapper, polymorphic_identity='repeating')
simple_holiday_mapper= mapper (SimpleHoliday,
inherits=holiday_mapper, polymorphic_identity='simple')
However, I'm not sure how to map the relationships with the
association table.
Points that I think are relevant are
1. It's only the UnionCalendar that has children.
2. Deleting a UnionCalendar should delete the entries in the
association table, but not the children calendars.
3. Navigation is really only needed from the parent UnionCalendar to
the underlying children calendars. However, having a collection back
the other way might have some uses.
4. For SimpleCalender to its Holidays, I haven't yet implemented the
cascaded delete, but I know how to do this.
Thanks
Nick
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[sqlalchemy] Re: Composite Pattern
Thanks - I'll try and test tonight.
On Mar 24, 4:29 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Mar 24, 2011, at 4:40 AM, Nickle wrote:
I'm trying to implement a Composite
Pattern,http://en.wikipedia.org/wiki/Composite_pattern
In this case its to represent some holiday calendars. I need to
implement a union calendar that is a collection of other calendars.
So a straightforward hierarchy. Calendar, abstract as the top level
class. SimpleCalendar that inherits from Calendar. Then a union
calendar that inherits from Calendar, but I need to implement
children, a collection of calendars.
So its a self referential hierarchy. The point to note is that one
calendar can appear in more than one union calendar, so its a self
referential many to many. Its certain I need an association table as a
result.
I'm not quite sure how to configure this.
I'm trying something along these lines
calendars_table = Table \
(
'calendars',
metadata,
Column ('id', Integer, primary_key=True),
Column ('code', String, nullable=False, unique=True),
Column ('name', String),
Column ('calendar_type', String (20), nullable=False),
Column ('monday', Boolean),
Column ('tuesday', Boolean),
Column ('wednesday', Boolean),
Column ('thurday', Boolean),
Column ('friday', Boolean),
Column ('saturday', Boolean),
Column ('sunday', Boolean)
)
calendar_children_table = Table \
(
'calendar_children',
metadata,
Column ('parent_id', Integer, ForeignKey ('calendars.id')),
Column ('child_id', Integer, ForeignKey ('calendars.id'))
)
calendar_mapper = mapper (Calendar, calendars_table,
polymorphic_on=calendars_table.c.calendar_type,
polymorphic_identity=calendar)
simple_calendar_mapper = mapper (SimpleCalendar,
inherits=calendar_mapper,
polymorphic_identity='simple',properties={'holidays':relationship(Holiday,
backref='calendar')})
union_calendar_mapper = mapper (UnionCalendar,
inherits=calendar_mapper, polymorphic_identity='union')
holidays_table = Table \
(
'holidays',
metadata,
Column ('id', Integer, primary_key=True),
Column ('holiday_type', String(20), nullable=False),
Column ('calendar_id', Integer, ForeignKey ('calendars.id')),
Column ('description', String ),
Column ('year', Integer),
Column ('month', Integer),
Column ('day', Integer)
)
holiday_mapper = mapper (Holiday, holidays_table,
polymorphic_on=holidays_table.c.holiday_type,
polymorphic_identity='holiday')
repeating_holiday_mapper = mapper (RepeatingHoliday,
inherits=holiday_mapper, polymorphic_identity='repeating')
simple_holiday_mapper = mapper (SimpleHoliday,
inherits=holiday_mapper, polymorphic_identity='simple')
However, I'm not sure how to map the relationships with the
association table.
Points that I think are relevant are
1. It's only the UnionCalendar that has children.
apply a relatlonship() to the UnionCalendar mapping, the target class is
Calendar, secondary is calendar_children_table.
2. Deleting a UnionCalendar should delete the entries in the
association table, but not the children calendars.
This is a given when using secondary with relationship. Severing the link
between parent and child corresponds to a deletion of the row in secondary.
3. Navigation is really only needed from the parent UnionCalendar to
the underlying children calendars. However, having a collection back
the other way might have some uses.
just add backref='parent_containers' or similar to the relationship().
4. For SimpleCalender to its Holidays, I haven't yet implemented the
cascaded delete, but I know how to do this.
Thanks
Nick
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[sqlalchemy] Re: Composite Pattern
Doesn't quite work.
What I think is the problem is that when using secondary on the
association table, there are two foreign keys both referencing a
calendar. It doesn't know which to pick.
union mapper looks like this
union_calendar_mapper = \
mapper \
(
UnionCalendar,
inherits=calendar_mapper,
polymorphic_identity='union',
properties =
{
'children':relationship(Calendar,
secondary='calendar_children_table')
}
)
On Mar 24, 4:29 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Mar 24, 2011, at 4:40 AM, Nickle wrote:
I'm trying to implement a Composite
Pattern,http://en.wikipedia.org/wiki/Composite_pattern
In this case its to represent some holiday calendars. I need to
implement a union calendar that is a collection of other calendars.
So a straightforward hierarchy. Calendar, abstract as the top level
class. SimpleCalendar that inherits from Calendar. Then a union
calendar that inherits from Calendar, but I need to implement
children, a collection of calendars.
So its a self referential hierarchy. The point to note is that one
calendar can appear in more than one union calendar, so its a self
referential many to many. Its certain I need an association table as a
result.
I'm not quite sure how to configure this.
I'm trying something along these lines
calendars_table = Table \
(
'calendars',
metadata,
Column ('id', Integer, primary_key=True),
Column ('code', String, nullable=False, unique=True),
Column ('name', String),
Column ('calendar_type', String (20), nullable=False),
Column ('monday', Boolean),
Column ('tuesday', Boolean),
Column ('wednesday', Boolean),
Column ('thurday', Boolean),
Column ('friday', Boolean),
Column ('saturday', Boolean),
Column ('sunday', Boolean)
)
calendar_children_table = Table \
(
'calendar_children',
metadata,
Column ('parent_id', Integer, ForeignKey ('calendars.id')),
Column ('child_id', Integer, ForeignKey ('calendars.id'))
)
calendar_mapper = mapper (Calendar, calendars_table,
polymorphic_on=calendars_table.c.calendar_type,
polymorphic_identity=calendar)
simple_calendar_mapper = mapper (SimpleCalendar,
inherits=calendar_mapper,
polymorphic_identity='simple',properties={'holidays':relationship(Holiday,
backref='calendar')})
union_calendar_mapper = mapper (UnionCalendar,
inherits=calendar_mapper, polymorphic_identity='union')
holidays_table = Table \
(
'holidays',
metadata,
Column ('id', Integer, primary_key=True),
Column ('holiday_type', String(20), nullable=False),
Column ('calendar_id', Integer, ForeignKey ('calendars.id')),
Column ('description', String ),
Column ('year', Integer),
Column ('month', Integer),
Column ('day', Integer)
)
holiday_mapper = mapper (Holiday, holidays_table,
polymorphic_on=holidays_table.c.holiday_type,
polymorphic_identity='holiday')
repeating_holiday_mapper = mapper (RepeatingHoliday,
inherits=holiday_mapper, polymorphic_identity='repeating')
simple_holiday_mapper = mapper (SimpleHoliday,
inherits=holiday_mapper, polymorphic_identity='simple')
However, I'm not sure how to map the relationships with the
association table.
Points that I think are relevant are
1. It's only the UnionCalendar that has children.
apply a relatlonship() to the UnionCalendar mapping, the target class is
Calendar, secondary is calendar_children_table.
2. Deleting a UnionCalendar should delete the entries in the
association table, but not the children calendars.
This is a given when using secondary with relationship. Severing the link
between parent and child corresponds to a deletion of the row in secondary.
3. Navigation is really only needed from the parent UnionCalendar to
the underlying children calendars. However, having a collection back
the other way might have some uses.
just add backref='parent_containers' or similar to the relationship().
4. For SimpleCalender to its Holidays, I haven't yet implemented the
cascaded delete, but I know how to do this.
Thanks
Nick
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[sqlalchemy] Re: Composite Pattern
Thanks - sort knew what was needed - didn't know how to express it.
Nick
On Mar 24, 10:20 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Mar 24, 2011, at 5:08 PM, Nickle wrote:
Doesn't quite work.
What I think is the problem is that when using secondary on the
association table, there are two foreign keys both referencing a
calendar. It doesn't know which to pick.
union mapper looks like this
union_calendar_mapper = \
mapper \
(
UnionCalendar,
inherits=calendar_mapper,
polymorphic_identity='union',
properties =
{
'children':relationship(Calendar,
secondary='calendar_children_table')
}
)
oh thats correct, so primaryjoin and secondaryjoin clear that up, also
you pass the Table object itself to secondary without the string:
relationship(Calendar, secondary=calendar_children_table,
primaryjoin=calendar_children_table.c.parent_id=calendars_table.c.id,
secondaryjoin=calendar_children_table.c.child_id=calendars_table.c.id
)
so it knows UnionCalendar id 12 linked to Calendar id 17, put the 12 in
parent_id, put the 17 in child_id. Similarly it knows which side is
which inside a query(UnionCalendar).join(children).
On Mar 24, 4:29 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On Mar 24, 2011, at 4:40 AM, Nickle wrote:
I'm trying to implement a Composite
Pattern,http://en.wikipedia.org/wiki/Composite_pattern
In this case its to represent some holiday calendars. I need to
implement a union calendar that is a collection of other calendars.
So a straightforward hierarchy. Calendar, abstract as the top level
class. SimpleCalendar that inherits from Calendar. Then a union
calendar that inherits from Calendar, but I need to implement
children, a collection of calendars.
So its a self referential hierarchy. The point to note is that one
calendar can appear in more than one union calendar, so its a self
referential many to many. Its certain I need an association table as a
result.
I'm not quite sure how to configure this.
I'm trying something along these lines
calendars_table = Table \
(
'calendars',
metadata,
Column ('id', Integer, primary_key=True),
Column ('code', String, nullable=False, unique=True),
Column ('name', String),
Column ('calendar_type', String (20), nullable=False),
Column ('monday', Boolean),
Column ('tuesday', Boolean),
Column ('wednesday', Boolean),
Column ('thurday', Boolean),
Column ('friday', Boolean),
Column ('saturday', Boolean),
Column ('sunday', Boolean)
)
calendar_children_table = Table \
(
'calendar_children',
metadata,
Column ('parent_id', Integer, ForeignKey ('calendars.id')),
Column ('child_id', Integer, ForeignKey ('calendars.id'))
)
calendar_mapper = mapper (Calendar, calendars_table,
polymorphic_on=calendars_table.c.calendar_type,
polymorphic_identity=calendar)
simple_calendar_mapper = mapper (SimpleCalendar,
inherits=calendar_mapper,
polymorphic_identity='simple',properties={'holidays':relationship(Holiday,
backref='calendar')})
union_calendar_mapper = mapper (UnionCalendar,
inherits=calendar_mapper, polymorphic_identity='union')
holidays_table = Table \
(
'holidays',
metadata,
Column ('id', Integer, primary_key=True),
Column ('holiday_type', String(20), nullable=False),
Column ('calendar_id', Integer, ForeignKey ('calendars.id')),
Column ('description', String ),
Column ('year', Integer),
Column ('month', Integer),
Column ('day', Integer)
)
holiday_mapper = mapper (Holiday, holidays_table,
polymorphic_on=holidays_table.c.holiday_type,
polymorphic_identity='holiday')
repeating_holiday_mapper = mapper (RepeatingHoliday,
inherits=holiday_mapper, polymorphic_identity='repeating')
simple_holiday_mapper = mapper (SimpleHoliday,
inherits=holiday_mapper, polymorphic_identity='simple')
However, I'm not sure how to map the relationships with the
association table.
Points that I think are relevant are
1. It's only the UnionCalendar that has children.
apply a relatlonship() to the UnionCalendar mapping, the target class is
Calendar, secondary is calendar_children_table.
2. Deleting a UnionCalendar should delete the entries in the
association table, but not the children calendars.
This is a given when using secondary with relationship. Severing the
link between parent and child corresponds to a deletion of the row in
secondary.
3. Navigation is really only needed from the parent UnionCalendar to
the underlying children calendars. However, having a collection back
the other way might have some uses.
just add backref='parent_containers' or similar
[sqlalchemy] SQLite and Dates
I have the following code. Simple Calendar and list of holidays. If I
try and use a Date and datetime.date I get an error as follows
Traceback (most recent call last):
File H:\workspace\Test\src\stest.py, line 78, in module
lon.holidays = [Holiday(lon,
holiday=datetime.date('2011-01-01'),description='New Year'),
Holiday(lon, holiday=datetime.date('2011-12-25'),description=xmas)]
TypeError: an integer is required
If I change it to use a string/String for the date, its fine.
I know there is an issue with Date and Sqlite but I can't fix it.
The String version is commented out in the holiday_tables code, and it
works
Any help appreciated
=
from sqlalchemy import create_engine
from sqlalchemy import Table, Column, Date , Integer, String,
MetaData, ForeignKey
from sqlalchemy.orm import relationship, backref
from sqlalchemy.orm import mapper
from sqlalchemy.orm import sessionmaker
import datetime
engine = create_engine('sqlite:///:memory:', echo=True)
Session = sessionmaker()
Session.configure(bind=engine)
session = Session()
metadata = MetaData()
class Calendar (object):
def __init__(self, name, fullname):
self.name = name
self.fullname = fullname
def __repr__(self):
return Calendar('%s','%s') % (self.name, self.fullname)
class Holiday (object):
def __init__(self, holiday, description):
self.holiday = holiday
self.description = description
def __repr__(self):
return Holiday('%s', '%s') % (self.holiday,
self.description)
calendars_table = Table \
(
'calendars',
metadata,
Column('id', Integer, primary_key=True),
Column('name', String),
Column('fullname', String)
)
holidays_table = Table \
(
'holidays',
metadata,
Column('id', Integer, primary_key=True),
#Column('holiday', String, nullable=False),
Column('holiday', Date, nullable=False),
Column('description', String),
Column('calendar_id', Integer, ForeignKey('calendars.id'))
)
metadata.create_all(engine)
mapper \
(
Calendar,
calendars_table,
properties= \
{
'holidays': relationship \
(
Holiday,
backref='calendar',
cascade=all, delete, delete-orphan,
lazy='joined'
)
}
)
mapper(Holiday, holidays_table)
session.commit()
lon = Calendar('LON', 'London')
#lon.holidays = [Holiday(holiday='2011-01-01',description='New Year'),
Holiday(holiday='2011-12-25',description=xmas)]
session.add(lon)
session.commit()
lon.holidays = [Holiday(lon,
holiday=datetime.date('2011-01-01'),description='New Year'),
Holiday(lon, holiday=datetime.date('2011-12-25'),description=xmas)]
session.commit()
lon = session.query(Calendar).filter_by(name='LON').one()
session.delete(lon)
session.commit()
=
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[sqlalchemy] Idempotent updating (Update or insert)
I'm trying to get my head around idempotent updating. ie I'm creating some objects, I want to store them. These objects might or might not be already stored in the database. If they are, I want to update them if necessary (a field has changed), or insert them if they do not exist. What's the preferred approach? Nick -- 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] Relationships in an inheritance heirarchy
I have the following python classes.
class Instrument (object):
def __init__ (self, name):
self.name = name
class Equity (Instrument):
def __init__ (self, name, currency_id):
Instrument.__init__(self, name)
self.currency_id = currency_id
class Currency (Instrument):
pass
Pretty simple cut down example. Equity has a relationship with a
currency
Mapping is as follows
instruments = Table ('instruments', metadata,
Column ('id', Integer, primary_key=True),
Column ('type', String (10), nullable=False),
Column ('name', String(50), nullable=False, unique=True),
Column ('currency_id', Integer, ForeignKey ('instruments.id'))
)
instrument_mapper = mapper (Instrument, instruments,
polymorphic_on=instruments.c.type, polymorphic_identity='instrument')
equity_mapper = mapper (Equity,
inherits=instrument_mapper, polymorphic_identity='equity')
currency_mapper = mapper (Currency,
inherits=instrument_mapper, polymorphic_identity='currency',
properties={'equities': relationship
(Instrument, backref=backref('currency',
remote_side=[instruments.c.id]))}
)
One thing I'm not sure about. The currency mapper should have a
relationship with Currency and not with Instruments. ie. I want to
restrict the relationship to Currencies.
Is there a standard way of going around this?
Nick
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