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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>
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