Fix for Select() + paging in LINQ. Closes GH-3337

src/LinqTests/Bugs/Bug_3337_select_page.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using Marten;
+using Marten.Pagination;
+using Marten.Testing.Documents;
+using Marten.Testing.Harness;
+using Shouldly;
+using Xunit.Abstractions;
+
+namespace LinqTests.Bugs;
+
+public class Bug_3337_select_page : BugIntegrationContext
+{
+    private readonly ITestOutputHelper _output;
+
+    public Bug_3337_select_page(ITestOutputHelper output)
+    {
+        _output = output;
+    }
+
+    [Fact]
+    public async Task try_it_out()
+    {
+        await theStore.BulkInsertAsync(Target.GenerateRandomData(1000).ToArray());
+
+        theSession.Logger = new TestOutputMartenLogger(_output);
+        var results = await theSession.Query<Target>().Where(x => x.Inner != null)
+            .Select(x => new SelectedGuy() { Id = x.Id, Number = x.Inner.Number, Text = x.String })
+            .Take(5).Stats(out var statistics).ToListAsync();
+            //.ToPagedListAsync(1, 5);
+
+        foreach (var result in results)
+        {
+            result.Number.ShouldNotBe(0);
+            result.Id.ShouldNotBe(Guid.Empty);
+            result.Text.ShouldNotBeNull();
+        }
+    }
+}
+
+public class SelectedGuy
+{
+    public int Number { get; set; }
+    public Guid Id { get; set; }
+    public string Text { get; set; }
+}

src/Marten/Linq/SqlGeneration/SelectDataSelectClause.cs

@@ -48,7 +48,13 @@ public void Apply(ICommandBuilder sql)
 
     public string[] SelectFields()
     {
-        return new[] { "data" };
+        // Fix for GH-3337
+        var builder = new CommandBuilder();
+        Selector.Apply(builder);
+
+        var fieldName = builder.Compile().CommandText;
+
+        return new[] { fieldName };
     }
 
     public ISelector BuildSelector(IMartenSession session)