Add an optional property parameter to DataLoaders methods.

[orlandommb]

Product

Green Donut

Is your feature request related to a problem?

I don't think its a problem is more of a inconvenience, if an Entity has relationships with more than one Entity, and i want to able to include those entities in my query i have to build one DataLoader for each relationship (im using EF Core) because there's no way to pass the property that i need to query for in the where clause of ef core.

For example, the models Products, Category and Company. Products has a CategoryId and CompanyId foreign keys, and Company and Category models have List Products navigation properties,

If i query for Company and want to include Products in my query i got a build a GroupedDataLoader that searches for products like:

context.Products.Where(p=> keys.Contains( p.CompanyId ))

If i query for Category and want to include Products in my query i got a build a GroupedDataLoader that searches for products like:

context.Products.Where(p=> keys.Contains( p.CategoryId ))

Right now my Products model has relationships with:

1. Company
2. Branch
3. Category
4. SubCategory
5. Unit
6. Tax

this means i have to make one GroupedDataLoader for each, at least thats how i know how to do it right now, don't know if theres a better way to do it.

The solution you'd like

Passing the property as a parameter in some way is the best solution that comes to my mind. I know that HotChocolate its made to work with multiple database providers but maybe with an optional parameter in the LoadBatchAsync method might work, something like Product.CategoryId.

[michaelstaib]

@PascalSenn would the observable cache solve this?

[PascalSenn]

@michaelstaib
Observable cache would not reduce the number of data loaders, but the total number of fetches.

You still need to have a DataLoader from each direction, but once fetched, the order data loaders could subscribe to the cache and also get prefilled.

Meaning, if I load the 2 via the ProductByCompanyIdDataLoader and I get { id: 1, companyId: 2, categoryId: 3}, then a call to ProductByCategoryIdDataLoader with id 3 would already be in the cache.

On another note, the behaviour that @orlandommb describes could theoretically already done with a datalaoder that has a polymorphic key.

public record ProductKey() 
{
     public record CustomerId(Guid CustomerId) : ProductKey
     public record BranchId(Guid CustomerId) : ProductKey
     public record CategoryId(Guid CustomerId) : ProductKey
     ...
}

[PascalSenn]

Thinking about it more, the observable cache would not help at all with GroupedDataLoaders, as there is no way to know if you have fetched all Products of a Category already.