autogenerated keys for entities with multipart keys - breeze

Question

I was trying to create a new object with multicolumn primary key formed by a foreign key and a self-generated field and I found this error:
Ids can not be autogenerated for entities with multipart keys.
For now, and although not the most appropriate, I will change the key but the question is:
Are you planning support multicolumn primary key autogenerated soon?
I will add the request to uservoice too.
A greeting.
Edit to explain the use case:
Hello,
True, it may not make sense to have a primary key composed by a foreign key and a self-generated field.
My idea was to build a table like this:
ParentID ChildID Data
1 1 Some Data...
1 2 Some Data...
2 1 Some Data...
2 2 Some Data...
As a first step I did a table like this:
ParentID ChildID Data
1 1 Some Data...
1 2 Some Data...
2 3 Some Data...
2 4 Some Data...
Where ChildID was a self-generated field.
So you can ignore my question.
A greeting.

Answer 1

I've had the same problem but I have successfully solved it without changing the Primary Key (PK).
My PK had 2 columns
ProductId (identity)
TenantId (multitenant application)
so the first problem was Breeze couldn't generate new PK when the new item was added to the EntityManager. And I have defined custom entity initialization function:
var manager = new breeze.EntityManager(breezeServiceUrl);
var store = manager.metadataStore;
function itemInitializer(item) {
if (item.ProductId() == 0) {
item.ProductId(/*Some counter value*/);
}
if (item.TenantId() == 0) {
item.TenantId(TenantId);
}
if (item.isBeingEdited === undefined) {
item.isBeingEdited = ko.observable(false);
}
};
store.registerEntityTypeCtor("ProductItem", function() {/*Leave empty to use default constructor*/}, itemInitializer);
The second problem is that Breeze couldn't update the ProductId with the real value from EntityFramework because it gets the entity by PK and the returned value had only ProductId. So you need to override the function:
var entityType = store.getEntityType("ProductItem");
var entityGroup = manager.findEntityGroup(entityType);
entityGroup._fixupKey = function (tempValue, realValue) {
var ix = this._indexMap[tempValue + ":::" + TenantId]; //Changed line
if (ix === undefined) {
throw new Error("Internal Error in key fixup - unable to locate entity");
}
var entity = this._entities[ix];
var keyPropName = entity.entityType.keyProperties[0].name;
entity.setProperty(keyPropName, realValue);
delete entity.entityAspect.hasTempKey;
delete this._indexMap[tempValue];
this._indexMap[realValue] = ix;
};
If you have any other questions about multipart keys, you can read it in the blog.

Answer 2

This feature is not currently on the roadmap, but I want to better understand your use case for this. As you already know, Breeze supports auto-generated keys, and Breeze supports multi-part keys, but what scenarios do you find using both at the same time to be helpful?
Thanks!

Answer 3

Actually having a multipart key where part of the key is autogenerated is actually pretty common. This usually occurs with legacy databases where the primary key consists of a foreign key property and a 'autogenerated' sequence number property. Usually this autogenerated key is not globally unique by itself, but only in conjunction with the foreign key property. Think of an orderDetail with a foreign key of "OrderId, SequenceNumber".
What doesn't seem to make as much sense is when the primary key consists of more than one autogenerated property.
In Breeze the autogenerated keys are intended to be globally unique. Whereas, in the multipart key mentioned above the SequenceNumber would not be globally unique ( and if it were then why not make it the primary key all by itself).
Does this make sense?