Query: Null TypeMapping in Sql Tree

See original GitHub issue

When using .Select to project into custom types you can run into this error when using the conditional operator. I’ve included a SSCE below, but the gist is this code here:

db.FirstEntities
    .Select(x => new FirstEntityModel
    {
        Id = x.Id,
        ThirdEntityId = x.ThirdEntity == null ? null : (int?)x.ThirdEntity.Id,
        SecondEntity = x.SecondEntity == null ? null : new SecondEntityModel()
    })
    .ToArray();

Interestingly, if I remove either the ThirdEntityId assignment or the SecondEntity assignment, there are no problems.

The full exception is:

System.InvalidOperationException
  HResult=0x80131509
  Message=The binary operator NotEqual is not defined for the types 'Microsoft.EntityFrameworkCore.Storage.ValueBuffer' and 'Microsoft.EntityFrameworkCore.Storage.ValueBuffer'.
  Source=System.Linq.Expressions
  StackTrace:
   at System.Linq.Expressions.Expression.GetEqualityComparisonOperator(ExpressionType binaryType, String opName, Expression left, Expression right, Boolean liftToNull)
   at System.Linq.Expressions.Expression.NotEqual(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at System.Linq.Expressions.Expression.NotEqual(Expression left, Expression right)
   at Microsoft.EntityFrameworkCore.Query.Expressions.Internal.NullConditionalExpression.Reduce()
   at System.Linq.Expressions.Expression.ReduceAndCheck()
   at System.Linq.Expressions.Expression.ReduceExtensions()
   at System.Linq.Expressions.Compiler.StackSpiller.RewriteExtensionExpression(Expression expr, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.RewriteExpression(Expression node, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.MemberAssignmentRewriter..ctor(MemberAssignment binding, StackSpiller spiller, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.BindingRewriter.Create(MemberBinding binding, StackSpiller spiller, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.RewriteMemberInitExpression(Expression expr, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.RewriteExpression(Expression node, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.RewriteExpressionFreeTemps(Expression expression, Stack stack)
   at System.Linq.Expressions.Compiler.StackSpiller.Rewrite[T](Expression`1 lambda)
   at System.Linq.Expressions.Expression`1.Accept(StackSpiller spiller)
   at System.Linq.Expressions.Compiler.LambdaCompiler.Compile(LambdaExpression lambda)
   at System.Linq.Expressions.LambdaExpression.Compile()
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.ProjectionShaper.Create(Shaper originalShaper, LambdaExpression materializer)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.VisitSelectClause(SelectClause selectClause, QueryModel queryModel)
   at Remotion.Linq.Clauses.SelectClause.Accept(IQueryModelVisitor visitor, QueryModel queryModel)
   at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.VisitQueryModel(QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.VisitQueryModel(QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateQueryExecutor[TResult](QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](QueryModel queryModel)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](Expression query, IQueryModelGenerator queryModelGenerator, IDatabase database, IDiagnosticsLogger`1 logger, Type contextType)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass13_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Remotion.Linq.QueryableBase`1.GetEnumerator()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at ConsoleApp2.Program.Main(String[] args) in C:\Users\Kirk\Documents\Visual Studio 2017\Projects\ConsoleApp2\ConsoleApp2\Program.cs:line 20

The full repro is to create a new .NET Core Console program, add Microsoft.EntityFrameworkCore and Microsoft.EntityFrameworkCore.Sqlite and make this your main Program.cs file:

using System;
using System.Linq;
using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            var connection = new SqliteConnection("DataSource=:memory:");
            connection.Open();
            var options = new DbContextOptionsBuilder<TestDb>()
                .UseSqlite(connection)
                .Options;
            var db = new TestDb(options);
            db.Database.EnsureCreated();

            db.FirstEntities
                .Select(x => new FirstEntityModel
                {
                    Id = x.Id,
                    ThirdEntityId = x.ThirdEntity == null ? null : (int?)x.ThirdEntity.Id,
                    SecondEntity = x.SecondEntity == null ? null : new SecondEntityModel()
                })
                .ToArray();
        }
    }

    public class TestDb : DbContext
    {
        public DbSet<FirstEntity> FirstEntities { get; set; }
        public DbSet<SecondEntity> SecondEntities { get; set; }
        public DbSet<ThirdEntity> ThirdEntities { get; set; }

        public TestDb(DbContextOptions options) : base(options)
        {
        }
    }

    public class FirstEntity
    {
        public int Id { get; set; }
        public int? OtherId { get; set; }
        public int? SecondEntityId { get; set; }

        public ThirdEntity ThirdEntity { get; set; }
        public SecondEntity SecondEntity { get; set; }
    }

    public class SecondEntity
    {
        public int Id { get; set; }
        public int? OtherId { get; set; }
    }

    public class ThirdEntity
    {
        public int Id { get; set; }
        public int? FirstEntityId { get; set; }

        public FirstEntity FirstEntity { get; set; }
    }

    public class FirstEntityModel
    {
        public int Id { get; set; }
        public int? ThirdEntityId { get; set; }
        public SecondEntityModel SecondEntity { get; set; }
    }

    public class SecondEntityModel
    {
        public int Id { get; set; }
    }
}

Further technical details

EF Core version: 2.1.4 EF Core Sqlite version: 2.1.4 Database Provider: Microsoft.EntityFrameworkCore.Sqlite Operating system: Windows 10 IDE: Visual Studio 2017 15.8.8

Issue Analytics

State:
Created 5 years ago
Comments:9 (3 by maintainers)

Top GitHub Comments

1reaction

divegacommented, Nov 2, 2018

Sorry for the dup! 😃

No worries @kswoll. We decided to use your issue to track this. Thanks for posting the workarounds.

0reactions

CliffordSpainhourcommented, Jun 12, 2020

I found a work around, but I don’t necessary like the solution. I’m not sure how this will affect performance.

In the Source Url Entity Class, I now always initialize the price as an empty POCO

    public class SiteProductSourceUrlEntity
    {
        public SiteProductSourceUrlEntity()
        {
            Price = new SiteProductPriceEntity();
        }

        public int Id { get; set; }
        public string Value { get; set; }
        
        public virtual SiteProductPriceEntity Price { get; set; }
        public int? VariationId { get; set; }
        public virtual SiteProductVariationEntity Variation { get; set; }
        public int SiteProductId { get; set; }
        public virtual SiteProductEntity SiteProduct { get; set; }
    }

I then changed the query to check with the price id instead of the price reference

var result = await context.SiteProducts.Where(x => x.Id == siteProductId).Select(p => new SiteProductModel
            {
                SourceUrls = p.SourceUrls.Select(e =>
                  new ProductSourceUrlModel
                  {
                      Id = e.Id,
                      Url = e.Value,
                      Price = e.Price.Id > 0 ? new ProductPriceModel
                      {
                          Id = e.Price.SiteProductSourceUrlId,
                          AmountMax = e.Price.AmountMax,
                          AmountMin = e.Price.AmountMin,
                          Currency = e.Price.Currency,
                          IsSale = e.Price.IsSale,
                          LastSeen = e.Price.LastSeen,
                          Merchant = e.Price.Merchant,
                          SourceUrl = e.Value,
                          Availability = e.Price.Availability
                      } : null,

                  }),
            }).FirstOrDefaultAsync();

Although this works, doing it this way has other negative affects. For example, I have to set any empty prices back to null in other queries using eager loading, otherwise it will try to save an empty price when persisting.

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