Bug: COALESCE uses only first and second argument

[boukeversteegh]

Summary:

It seems impossible to generate COALESCE(a, b, c, d). Only COALESCE(a, b) will be generated.

Details:

I have a custom localization function that is defined as such:

modelBuilder
            .HasDbFunction(
                typeof(MyDbContext)
                    .GetMethod(nameof(Localize),
                        new[] { typeof(Dictionary<string, string>), typeof(string[]) })!
            )
            .HasTranslation(args => {
               var languages = ((SqlConstantExpression)args[1]).Value as string[];
               var arguments = MakeLanguageFieldsExpressions(languages);
               return new SqlFunctionExpression(
                    "COALESCE",
                    arguments,
                    false,
                    new bool[arguments.Length],
                    typeof(string),
                    null
                );
           });

Now in a LINQ query, I can call Items.select(item => new LocalizedItem { title = Localize(item, new [] {"en", "de"} ) } , and the query will be translated to (details omitted):

SELECT COALESCE(e."Title"#>>'{en,value}', e."Title"#>>'{de,value}') AS "Title"

This works great, however this only works with 2 coalescing arguments. Anything after the 2nd argument is never generated into SQL.

How can I work around this limitation?

[boukeversteegh]

Apparently this is fixed in EF Core 7.

Solved using EF Core 7 with Dotnet 6.

[boukeversteegh]

dotnet/efcore#26419

dotnet/efcore#26344