NavigationExpandingExpressionVisitor moves Select() behind DefaultIfEmpty() #36208
Description
Question
Hello,
I am currently writing an EntityFramework Provider. While translating the expression produced by NorthwindSelectQueryTestBase.SelectMany_correlated_with_outer_3, I noticed that the NavigationExpandingExpressionVisitor moves the .Select(o => c.City) behind the .DefaultIfEmpty().
I'm probably missing something, but this seems wrong, as
Enumerable.Empty().DefaultIfEmpty().Select(x => "foo")
is not the same as
Enumerable.Empty().Select(x => "foo").DefaultIfEmpty()
So now I'm left wondering how to handle this, because there are valid uses for both cases. Once the NavigationExpandingExpressionVisitor transforms the expression however I can no longer distinguish between these cases.
I would be very thankful if you could give me some pointers on what the actual behaviour should be.
Best Regards
Your code
NorthwindSelectQueryTestBase.SelectMany_correlated_with_outer_3:
from c in ss.Set<Customer>()
from o in ss.Set<Order>().Where(o => c.CustomerID == o.CustomerID).Select(o => c.City).DefaultIfEmpty()
select new { c, o }
Here's what the query looks like just before and after the call to the NavigationExpandingExpressionVisitor in QueryTranslationPreprocessor.cs Process(Expression query)
Before NavigationExpandingExpressionVisitor:
[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression]
.SelectMany(c =>
[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression]
.Where(o => (c.CustomerID == o.CustomerID))
.Select(o => c.City)
.DefaultIfEmpty(),
(c, o) => new <>f__AnonymousType0`2(c = c, o = o)
)
After NavigationExpandingExpressionVisitor:
[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression]
.SelectMany(c =>
[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression]
.Where(o => (c.CustomerID == o.CustomerID))
.DefaultIfEmpty()
.Select(o => c.City),
(c, c) => new TransparentIdentifier`2(Outer = c, Inner = c))
.Select(ti => new <>f__AnonymousType0`2(c = ti.Outer, o = ti.Inner))Stack traces
Verbose output
EF Core version
9.0.0
Database provider
No response
Target framework
.NET 9.0
Operating system
No response
IDE
No response