Apparently, the reason why updates won't save is a sequence issue as
found here:
http://railspikes.com/2009/3/6/duplicate-key-violates-unique-constraint
So I suppose I need to do something like this: select
setval('children_id_seq', (select max(id) + 1 from children));
I have two questions as I am not a DBA:
1) When exactly do I do this? Every time I want to insert a child
record?
2) Why doesn't DataMapper handle this? Maybe I am spoiled by using
Hibernate in the Java world, but they handle sequences fairly easily
by using what they call dialects. I assumed the database-specific
DataMapper gems would do something similar. Or maybe they do and I am
just missing it?
Thanks.
On Jan 13, 1:14 pm, Neil Chaudhuri <[email protected]> wrote:
> I have been able to create a 1:M relationship using DataMapper and
> update the child items as well after creation. However, I have been
> unable to add to that collection.
>
> Let's say I have
>
> class Parent
> include DataMapper::Resource
>
> property :id, Serial
> ...
>
> has n, :children
> end
>
> class Child
> include DataMapper::Resource
>
> property :id, Serial
> ...
> belongs_to :parent
> end
>
> Whenever I try to add to the child collection belonging to a certain
> parent instance, I get either DataMapper::UpdateConflictError or
> "DataObjects::IntegrityError: ERROR: duplicate key value violates
> unique constraint "children_pkey" DETAIL: Key (id)=(1) already
> exists.
>
> I have tried a whole host of approaches. The most promising seemed
> parent.children.create(attributes), but that led to the
> IntegrityError. What is the preferred approach for adding a new item
> to the collection?
>
> Thanks.
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