HasDbFunction to an otherwise unmapped entity causes strange migration behavior

[julielerman]

File a bug

Apologies for my inability to describe this better in the title.

I have a class that I'm using to map to a TVF. It is configured as a keyless entity. It is not used for any other purpose and I do not need to map it to a table or view.

I initially migrated the model including seed data and then created the database from that migration.

Then I manually added a Table-Valued Function to the database. Running my demo, the mappings for the TVF work as expected and I can use them in queries.

The issue is related to migrating this model. I wanted to have a clean slate and include the functions in their own migration file.

Therefore, I deleted the migrations folder completely and then ran add-migration init. The resulting migration looked great. The class that the TVF was mapping to was not being picked up for table creation.

Next I needed an empty migration for the sake of providing the SQL to create the function. When I ran add-migration a second time, rather than empty UP and DOWN methods, migrations added "DROP TABLE" in UP and "CREATE TABLE" in DOWN for the table that was inferred by the class I defined for the mapping.

What I expected of course was an empty migration file.

Include your code

Here is the second migration file. The rest of the repo is on github at: https://github.com/julielerman/MappingDemo/tree/tvfonly

public partial class init2 : Migration
 {
     protected override void Up(MigrationBuilder migrationBuilder)
     {
         migrationBuilder.DropTable(
             name: "CustWithTotalClass");
     }

     protected override void Down(MigrationBuilder migrationBuilder)
     {
         migrationBuilder.CreateTable(
             name: "CustWithTotalClass",
             columns: table => new
             {
                 Name = table.Column<string>(type: "nvarchar(max)", nullable: true),
                 TotalSpent = table.Column<int>(type: "int", nullable: false)
             },
             constraints: table =>
             {
             });
     }
 }

I have experimented with this problem numerous times always with the same result. To be clear, I am literally running add-migration twice in a row without making any changes.

Thanks for either pointing out what I have done wrong (and sorry for wasting your time in addition to my own :( ) or confirming that there ism, indeed, something fishy going on here.

Include provider and version information

EF Core version: 5.0.7
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 5.0
Operating system: Windows 10
IDE: Visual Studio 2019 16.10.2

[AndriySvyryd]

This is "fixed" in 6.0 via #25034 as HasDbFunction no longer removes the table mapping. However we should consider patching it in 5.0.x

@julielerman I can't access the repro repo.

[julielerman]

THanks. Definitely aware of the table mapping removal issue and needing to explicitly re-map the table if your hasdbfunction is pointing to an existing one. (n my case I did NOT want a table anyway. But I did not realize that what I was seeing was related. But WHY is this showing up in a SECOND migration? Well if that's all part of the problem in #25034 then I won't worry about it. However perhaps this additional side effect should be documented as well. What do you think?

Also [facepalm], repo defaulted to private when I uploaded it from VS and I forgot to change it. It's public now.