Query: EntityEqualityRewritingExpressionVisitor doesn't work with object.Equals method

[maumar]

from c1 in ctx.Customers
from c2 in ctx.Customers
where c1.CustomerID == "ALFKI"
where c1 == c2
select c1.CustomerID

works fine (returns 1 result), however:

from c1 in ctx.Customers
from c2 in ctx.Customers
where c1.CustomerID == "ALFKI"
where c1.Equals(c2)
select c1.CustomerID

doesn't return any results, basically we perform client eval here and do reference comparison between c1 and c2. This works ok for collections (apart from the predicate being executed on the client), but returns unexpected results if we compare collections:

from c1 in ctx.Customers
from c2 in ctx.Customers
where c1.CustomerID == "ALFKI"
where c1Orders.Equals(c2.Orders)
select c1.CustomerID

The query above returns no results.

We should handle this case also, for the most part should be a matter of translating it to c1 == c2 and revisiting. Just need to detect a case when types are not matching - in case of binary expression, compiler handles that for us, but Equals method is loosely typed

[smitpatel]

Interesting, shouldn't c1 & c2 should resolve to single tracked reference in the context?

[maumar]

It actually works for entities, but not for entity collections (updated the original description)

This is probably because we materialize both collections with MaterializeCollectionNavigation, creating new instances every time. Here is the query plan:

(QueryContext queryContext) => IEnumerable<<>f__AnonymousType68<string, string>> _InterceptExceptions(
    source: IEnumerable<<>f__AnonymousType68<string, string>> _Select(
        source: IEnumerable<TransparentIdentifier<ValueBuffer, ValueBuffer>> _Where(
            source: IEnumerable<TransparentIdentifier<ValueBuffer, ValueBuffer>> _ShapedQuery(
                queryContext: queryContext, 
                shaperCommandContext: SelectExpression: 
                    SELECT [c1].[CustomerID] AS [Id1], [c2].[CustomerID] AS [Id2]
                    FROM [Customers] AS [c1]
                    CROSS JOIN [Customers] AS [c2]
                    WHERE ([c1].[CustomerID] = N'ALFKI') AND ([c2].[CustomerID] = N'ALFKI'), 
                shaper: TypedCompositeShaper<ValueBufferShaper, ValueBuffer, ValueBufferShaper, ValueBuffer, TransparentIdentifier<ValueBuffer, ValueBuffer>>), 
            predicate: (TransparentIdentifier<ValueBuffer, ValueBuffer> t0) => bool ICollection<Order> MaterializeCollectionNavigation(
                navigation: Customer.Orders, 
                elements: IEnumerable<Order> _InjectParameters(
                    queryContext: queryContext, 
                    source: IEnumerable<Order> _ShapedQuery(
                        queryContext: queryContext, 
                        shaperCommandContext: SelectExpression: 
                            SELECT [o].[OrderID], [o].[CustomerID], [o].[EmployeeID], [o].[OrderDate]
                            FROM [Orders] AS [o]
                            WHERE @_outer_CustomerID = [o].[CustomerID], 
                        shaper: BufferedEntityShaper<Order>), 
                    parameterNames: new string[]{ "_outer_CustomerID" }, 
                    parameterValues: new object[]{ string TryReadValue(t0.Outer, 0, Customer.CustomerID) })).Equals(ICollection<Order> MaterializeCollectionNavigation(
                    navigation: Customer.Orders, 
                    elements: IEnumerable<Order> _InjectParameters(
                        queryContext: queryContext, 
                        source: IEnumerable<Order> _ShapedQuery(
                            queryContext: queryContext, 
                            shaperCommandContext: SelectExpression: 
                                SELECT [o0].[OrderID], [o0].[CustomerID], [o0].[EmployeeID], [o0].[OrderDate]
                                FROM [Orders] AS [o0]
                                WHERE @_outer_CustomerID1 = [o0].[CustomerID], 
                            shaper: BufferedEntityShaper<Order>), 
                        parameterNames: new string[]{ "_outer_CustomerID1" }, 
                        parameterValues: new object[]{ string TryReadValue(t0.Inner, 1, Customer.CustomerID) })))), 
        selector: (TransparentIdentifier<ValueBuffer, ValueBuffer> t0) => new <>f__AnonymousType68<string, string>(
            string TryReadValue(t0.Outer, 0, Customer.CustomerID), 
            string TryReadValue(t0.Inner, 1, Customer.CustomerID)
        )), 
    contextType: Specification.Tests.TestModels.Northwind.NorthwindContext, 
    logger: DiagnosticsLogger<Query>, 
    queryContext: queryContext)

@anpete @divega - thoughts?

[anpete]

Looks like same issue as #7569. MaterializeCollectionNavigation is by-passing everything 🐛

[maumar]

Fixed in c4129dc