C#•12mo ago

Polymorphic query handling in EF Core - Thoughts?

So I'm having to deal a lot with entity polymorphism and querying the db to avoid having to execute multiple separate queries. I'm not sure about best practices here, but i also have to eagerload certain nav props from the derived types. Anyone know a better way than this?

        private async Task<IReadOnlyList<CoreProduct>> GetCoreProducts(IEnumerable<IProductRequest> requests, int internalPropertyId)
        {
            var query = _dbContext.Products.OfType<CoreProduct>().AsSplitQuery();

            foreach(var request in requests.GroupBy(x => x.GetType(), x => x))
            {
                query = request switch
                {
                    IAccommodationRequest => AccommodationQuery(query),
                    // more types here
                    _ => throw new UnreachableException()
                };
            }

            return await query.Where(x => x.InternalPropertyId == internalPropertyId && requests.Select(x => x.ProductId).Contains(x.Id)).ToListAsync();
        }

        private IQueryable<CoreProduct> AccommodationQuery(IQueryable<CoreProduct> query)
            => query = query.OfType<InternalAccommodation>().Include(x => x.PriceDetails);

        private async Task<IReadOnlyList<CoreProduct>> GetCoreProducts(IEnumerable<IProductRequest> requests, int internalPropertyId)
        {
            var query = _dbContext.Products.OfType<CoreProduct>().AsSplitQuery();

            foreach(var request in requests.GroupBy(x => x.GetType(), x => x))
            {
                query = request switch
                {
                    IAccommodationRequest => AccommodationQuery(query),
                    // more types here
                    _ => throw new UnreachableException()
                };
            }

            return await query.Where(x => x.InternalPropertyId == internalPropertyId && requests.Select(x => x.ProductId).Contains(x.Id)).ToListAsync();
        }

        private IQueryable<CoreProduct> AccommodationQuery(IQueryable<CoreProduct> query)
            => query = query.OfType<InternalAccommodation>().Include(x => x.PriceDetails);

9 Replies

FestivalDelGelato•12mo ago

you can use .Include(_ => (_ as InternalAccommodation).PriceDetails)

linqisniceOP•12mo ago

hmm yeah that might be cleaner, but then I have to suppress the null warning on the cast

FestivalDelGelato•12mo ago

yeah the warning is a little bothering

linqisniceOP•12mo ago

could place the switch in its own class and namespace and use pragma warning disable lol

FestivalDelGelato•12mo ago

it doesn't look to me that you really need thet switch i mean it depends on how you want to organize the code

linqisniceOP•12mo ago

ur probably right, at that point its just building the query and it doesn't impact performance either way if none of those requests are materialized if they don't exist

FestivalDelGelato•12mo ago

seems a quite wild query why is not PriceDetails in CoreProduct?

linqisniceOP•12mo ago

beacuse different products have different price details

FestivalDelGelato•12mo ago

and why a single query is trying to extract such heterogeneous objects/relations?

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Polymorphic query handling in EF Core - Thoughts?

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