Hey Mike,
Speaking from a debugging point of view, it might be useful if error messages
get more text then just "it failed, and died". Even if you just attached your
paragraph at the bottom starting "So when the..." either to the error itself
(always useful!) or somewhere in the docs (which, docstrings or no, don't have
any instances of 'syncrule' in them) it would put that snippet in the first
couple of places someone encountering the error is going to look. So maybe a
"Error Messages" section at the end of the docs?
-G
On Sunday, April 23, 2006, 9:42:49 PM, you wrote:
> a syncrule is an object generated internally when you associate one
> Mapper with another Mapper via a relation(), which is actually an
> object called a PropertyLoader.
> so lets use the Users/Address example. say we have classes User and
> Address. the join condition is
> users.c.user_id==addresses.c.user_id . When you attach the Address
> to the User and do a save, the "user_id" property of the User object
> is copied to the Address object. That is done by a syncrule. The
> syncrule is generated at mapper construction time by looking at the
> tables inside of "users.c.user_id==addresses.c.user_id", i.e. "users"
> and "addresses", matching those up to the mappers for the User and
> Address classes, and correlating the "user_id" column to the
> appropriate attribute in the User and Address class. the SyncRule
> then has an execute() method that is called at save time, which
> copies a single attribute from source to destination, in this case
> copying the "user_id" attribute from a User object to an Address object.
> So when the relation system has that error with "no syncrules
> generated", its a sign that the join conditions of the relationship
> do not correspond to the tables represented by the mappers.
> the code for this is pretty well isolated and docstring'ed in the
> module sqlalchemy.mapping.sync, containing the two objects
> ClauseSynchronizer and SyncRule.
> On Apr 23, 2006, at 1:50 PM, Gambit wrote:
>> Hey All,
>>
>> For the line:
>> Customer.mapper.add_property('checkout_history', relation
>> (CheckoutEntry.mapper, t_customer_tours,
>> primaryjoin=Customer.c.cust_id==CustomerTour.c.cust_id,
>> secondaryjoin=and_(CustomerTour.c.start_date <=
>> CheckoutEntry.c.ts_checkout,
>>
>>
>> CoreDb.CustomerTour.c.finish_date >= CheckoutEntry.c.ts_checkout)))
>> it generates the following error:
>>
>> ArgumentError: No syncrules generated for join criterion
>> customer_tours.start_date <= checkout_trail.ts_checkout AND
>> customer_tours.finish_date >= checkout_trail.ts_checkout
>>
>> It turns out that that property is, well, not what I wanted in the
>> first place
>> (there's no explicit 1:1 relationship between Customer and
>> CustomerTour,
>> amongst other things) but I am pretty curious what a syncrule is,
>> what causes
>> it to be generated (or not generated), and, if I encounter it
>> again, what
>> should I look for?
>>
>> I'm sure it must make sense to /someone/, but as a user I'm left
>> scratching my
>> head :)
>>
>> Cheers,
>> -G
>>
>>
>>
>>
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