[sqlalchemy] Many to Many and Unique Object question
I've got a many to many relationship with the association table. The issue
I am running into is that a given pesticide entry may have a pest or pests
already in the pest table. I don't want to add the pest since it will be a
duplicate, however I still want the association of that pest to the
pesticide done.
I've looked at the Unique Object wiki, however I am not sure that solves my
issue. Is there a way that SQLAlchemy can handle this, or do I need to
manually build the entries in the PestToPesticide association table?
Thanks!
Dan
PestToPesticide = Table('pest_to_pesticide', Base.metadata,
Column('pesticide_id', Integer,
ForeignKey('pesticide.row_id')),
Column('pest_id', Integer,
ForeignKey('pest.row_id'))
)
class Pesticide(Base):
__tablename__ = 'pesticide'
row_id =
Column(Integer,primary_key=True)
name = Column(String(64), unique=True)
pestList =relationship(Pest,
secondary=PestToPesticide, backref=pesticide)
class Pest(object):
row_id =
Column(Integer,primary_key=True)
name = Column(String(), unique=True)
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Re: [sqlalchemy] Many to Many and Unique Object question
pesttopesticide is maintained by relationship() as the secondary table, but
the expectation is that rows in this table will be unique. if you are
appending duplicate entries to pestList or pesticide you may want to use
collection_class=set to maintain uniqueness in the collection.
On Apr 24, 2013, at 12:51 PM, dan d...@inlet.geol.sc.edu wrote:
I've got a many to many relationship with the association table. The issue I
am running into is that a given pesticide entry may have a pest or pests
already in the pest table. I don't want to add the pest since it will be a
duplicate, however I still want the association of that pest to the pesticide
done.
I've looked at the Unique Object wiki, however I am not sure that solves my
issue. Is there a way that SQLAlchemy can handle this, or do I need to
manually build the entries in the PestToPesticide association table?
Thanks!
Dan
PestToPesticide = Table('pest_to_pesticide', Base.metadata,
Column('pesticide_id', Integer,
ForeignKey('pesticide.row_id')),
Column('pest_id', Integer,
ForeignKey('pest.row_id'))
)
class Pesticide(Base):
__tablename__ = 'pesticide'
row_id = Column(Integer,primary_key=True)
name = Column(String(64), unique=True)
pestList =relationship(Pest, secondary=PestToPesticide,
backref=pesticide)
class Pest(object):
row_id = Column(Integer,primary_key=True)
name = Column(String(), unique=True)
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Re: [sqlalchemy] Many to Many and Unique Object question
Using the collection_class=set is only going to work if I try to add the
same pest multiple times into pestList isn't it?
My situation is more along the lines that the pest table already has the
pest, and the pesticide I want to add also will have that pest, so I want
the entries in the pest_to_pesticide created. What currently happens is an
IntegrityError is thrown complaining that there is a duplicate pest entry.
On Wednesday, April 24, 2013 1:24:59 PM UTC-4, Michael Bayer wrote:
pesttopesticide is maintained by relationship() as the secondary table,
but the expectation is that rows in this table will be unique. if you are
appending duplicate entries to pestList or pesticide you may want to
use collection_class=set to maintain uniqueness in the collection.
On Apr 24, 2013, at 12:51 PM, dan d...@inlet.geol.sc.edu javascript:
wrote:
I've got a many to many relationship with the association table. The issue
I am running into is that a given pesticide entry may have a pest or pests
already in the pest table. I don't want to add the pest since it will be a
duplicate, however I still want the association of that pest to the
pesticide done.
I've looked at the Unique Object wiki, however I am not sure that solves
my issue. Is there a way that SQLAlchemy can handle this, or do I need to
manually build the entries in the PestToPesticide association table?
Thanks!
Dan
PestToPesticide = Table('pest_to_pesticide', Base.metadata,
Column('pesticide_id', Integer,
ForeignKey('pesticide.row_id')),
Column('pest_id', Integer,
ForeignKey('pest.row_id'))
)
class Pesticide(Base):
__tablename__ = 'pesticide'
row_id =
Column(Integer,primary_key=True)
name = Column(String(64), unique=True)
pestList =relationship(Pest,
secondary=PestToPesticide, backref=pesticide)
class Pest(object):
row_id =
Column(Integer,primary_key=True)
name = Column(String(), unique=True)
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Re: [sqlalchemy] Many to Many and Unique Object question
On Apr 24, 2013, at 1:38 PM, dan d...@inlet.geol.sc.edu wrote:
Using the collection_class=set is only going to work if I try to add the same
pest multiple times into pestList isn't it?
My situation is more along the lines that the pest table already has the
pest, and the pesticide I want to add also will have that pest, so I want the
entries in the pest_to_pesticide created. What currently happens is an
IntegrityError is thrown complaining that there is a duplicate pest entry.
well the issue of the pest_to_pesticide table and the unique entries in Pest
are two separate things. since this is many to many, sure any number of Pests
can be associated with any number of Pesticides, so to achieve this you of
course need to work with an existing Pest entry and associate it as needed.
Typically, if you know what Pest you want to work with, you look it up in the
database, if its not there, you create it. The UniqueObject recipe is one way
to make this more invisible but it isn't a requirement.Just to get things
to work you might want to keep it simple and just do a get_or_create_pest()
function, before turning it into something more transparent.
On Wednesday, April 24, 2013 1:24:59 PM UTC-4, Michael Bayer wrote:
pesttopesticide is maintained by relationship() as the secondary table, but
the expectation is that rows in this table will be unique. if you are
appending duplicate entries to pestList or pesticide you may want to use
collection_class=set to maintain uniqueness in the collection.
On Apr 24, 2013, at 12:51 PM, dan d...@inlet.geol.sc.edu wrote:
I've got a many to many relationship with the association table. The issue I
am running into is that a given pesticide entry may have a pest or pests
already in the pest table. I don't want to add the pest since it will be a
duplicate, however I still want the association of that pest to the
pesticide done.
I've looked at the Unique Object wiki, however I am not sure that solves my
issue. Is there a way that SQLAlchemy can handle this, or do I need to
manually build the entries in the PestToPesticide association table?
Thanks!
Dan
PestToPesticide = Table('pest_to_pesticide', Base.metadata,
Column('pesticide_id', Integer,
ForeignKey('pesticide.row_id')),
Column('pest_id', Integer,
ForeignKey('pest.row_id'))
)
class Pesticide(Base):
__tablename__ = 'pesticide'
row_id = Column(Integer,primary_key=True)
name = Column(String(64), unique=True)
pestList =relationship(Pest, secondary=PestToPesticide,
backref=pesticide)
class Pest(object):
row_id = Column(Integer,primary_key=True)
name = Column(String(), unique=True)
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Re: [sqlalchemy] Many to Many and Unique Object question
Cool, that's what I wanted to know. I didn't want to miss some function
that did this for me if it was there.
Thanks alot for the help!
Dan
On Wednesday, April 24, 2013 1:42:39 PM UTC-4, Michael Bayer wrote:
On Apr 24, 2013, at 1:38 PM, dan d...@inlet.geol.sc.edu javascript:
wrote:
Using the collection_class=set is only going to work if I try to add the
same pest multiple times into pestList isn't it?
My situation is more along the lines that the pest table already has the
pest, and the pesticide I want to add also will have that pest, so I want
the entries in the pest_to_pesticide created. What currently happens is an
IntegrityError is thrown complaining that there is a duplicate pest entry.
well the issue of the pest_to_pesticide table and the unique entries in
Pest are two separate things. since this is many to many, sure any number
of Pests can be associated with any number of Pesticides, so to achieve
this you of course need to work with an existing Pest entry and associate
it as needed. Typically, if you know what Pest you want to work with, you
look it up in the database, if its not there, you create it. The
UniqueObject recipe is one way to make this more invisible but it isn't a
requirement.Just to get things to work you might want to keep it simple
and just do a get_or_create_pest() function, before turning it into
something more transparent.
On Wednesday, April 24, 2013 1:24:59 PM UTC-4, Michael Bayer wrote:
pesttopesticide is maintained by relationship() as the secondary table,
but the expectation is that rows in this table will be unique. if you are
appending duplicate entries to pestList or pesticide you may want to
use collection_class=set to maintain uniqueness in the collection.
On Apr 24, 2013, at 12:51 PM, dan d...@inlet.geol.sc.edu wrote:
I've got a many to many relationship with the association table. The
issue I am running into is that a given pesticide entry may have a pest or
pests already in the pest table. I don't want to add the pest since it will
be a duplicate, however I still want the association of that pest to the
pesticide done.
I've looked at the Unique Object wiki, however I am not sure that solves
my issue. Is there a way that SQLAlchemy can handle this, or do I need to
manually build the entries in the PestToPesticide association table?
Thanks!
Dan
PestToPesticide = Table('pest_to_pesticide', Base.metadata,
Column('pesticide_id', Integer,
ForeignKey('pesticide.row_id')),
Column('pest_id', Integer,
ForeignKey('pest.row_id'))
)
class Pesticide(Base):
__tablename__ = 'pesticide'
row_id =
Column(Integer,primary_key=True)
name = Column(String(64), unique=True)
pestList =relationship(Pest,
secondary=PestToPesticide, backref=pesticide)
class Pest(object):
row_id =
Column(Integer,primary_key=True)
name = Column(String(), unique=True)
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