On Jul 9, 2012, at 4:48 AM, alex bodnaru wrote:
>
> hello michael, friends,
>
> after successfuly fixing the ddl by the append_constraint event, the relations
> that needed the said foreign keys remained orphan, asking for a foreign_keys
> argument and failing to load the remote table:
>
> class Lang(DeclarativeBase):
> lang_code = Column(String(20), primary_key=True)
> lang_name = Column(String(20))
>
> class PageData(DeclarativeBase):
> lang_code = Column(String(20), primary_key=True) # this foreign key is
> being
> successfully appended on before_create.
> lang = relation('Lang', backref='pages',
> primaryjoin=lang_code==Lang.lang_code) #this relationship won't work, since at
> the moment the class is being made, the foreign key is not there yet.
>
> the foreign_keys=Lang.lang_code arg does calm the exception, but doesn't do
> the
> work.
> could i add the relationship to the mapper on the same event?
I would think "foreign_keys" should fix the problem totally, what do you mean
"doesn't do the work"? I'd have to work up a test case, can you just throw
these two classes, the event, and some imports into a file for me ? I can just
run it.
>
> thank in advance,
> alex
>
> On 07/07/2012 05:13 PM, Michael Bayer wrote:
>> sure engine and connection have .dialect.name. Foreign key constraints
>> don't matter on SQLite unless you've actually enabled them, which is rare.
>> I'd still use an event though so at least the behavior is transparent.
>>
>> @event.listens_for(my_table, "before_create")
>> def add_fk(table, conn, **kw):
>> if conn.dialect.name != 'mssql':
>> table.append_constraint(ForeignKeyConstraint(...))
>>
>> tricky though to modify the table metadata within a "create" event in the
>> case that the table is created multiple times in an app. you can put a flag
>> in table.info, like "table.info['added_the_fk'] = True", to keep track of
>> things.
>>
>>
>>
>> On Jul 7, 2012, at 12:59 AM, alex bodnaru wrote:
>>
>>>
>>> hello mike and thanks for your answer.
>>>
>>> no problem with ForeignKeyConstraint, but wouldn't AddConstraint go the
>>> alter
>>> way? in this case, it will be ignored by the sqlite dialect.
>>>
>>> what i was looking for was more like:
>>>
>>> from sqlalchemy... import get_dialect
>>>
>>> ....
>>> fk_parms = dict(.....)
>>> if get_dialect() != 'mssql':
>>> fk_parms.update(onupdate='restrict')
>>> fk = ForeignKey(**fk_parms)
>>>
>>> would the dialect be accessible from the engine, metadata etc?
>>>
>>> thanks in advance,
>>> alex
>>>
>>>
>>> On 07/06/2012 11:39 PM, Michael Bayer wrote:
>>>> you'd use ForeignKeyConstraint along with the AddConstraint directive, and
>>>> limit it per-dialect using create/drop events as documented at
>>>> http://docs.sqlalchemy.org/en/rel_0_7/core/schema.html#controlling-ddl-sequences
>>>> .
>>>>
>>>>
>>>> On Jul 6, 2012, at 1:30 PM, alex bodnaru wrote:
>>>>
>>>>>
>>>>> hello friends,
>>>>>
>>>>> i need to define a foreign key differently for different dialects:
>>>>> ondelete='restrict' for most engines, but nothing (implied and not
>>>>> recognized)
>>>>> for mssql.
>>>>>
>>>>> could you help?
>>>>>
>>>>> thanks in advance,
>>>>> alex
>>>>>
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>>>>
>>>
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