EF 9 much slower than EF 8

[f0ppa21]

File a bug

EF 9 is much slower in our project on queries that results in a large/complex data-model.
When returning 2700 records in the example below the operation takes more than double the time in EF 9 compared to EF 8:
2.8 sec vs. 1.2 sec
With more returned records this difference also gets exponentially worse.

The generated Sql-query (using split query) itself is not slower (has checked with SQL Profiler), it seems that the ToListAsync-operation is much slower than in EF 8?!

We have now reverted to use EF 8 with .NET 9, but are hoping you can fix this in upcoming EF-patches!

Include your code

var drivningsenheter = await _context.Drivningsenheter
.Include(d => d.Taxeringsvolymer)
.Include(d => d.SchemalagdaDrivningar).ThenInclude(p => p.Lag)
.Include(d => d.SchemalagdaDrivningar).ThenInclude(p => p.Produktionsledare)
.Include(d => d.SchemalagdaDrivningar).ThenInclude(p => p.Produktionsomrade)
.Include(d => d.SchemalagdaDrivningar).ThenInclude(p => p.SchemalagdaVolymer).ThenInclude(p => p.DestineringSortiment).ThenInclude(s => s.ProduceratHandelssortiment)
.Include(d => d.SchemalagdaDrivningar).ThenInclude(p => p.SchemalagdaVolymer).ThenInclude(p => p.DestineringMottagningsplats).ThenInclude(s => s.Mottagningsplats)
.Include(d => d.Viapunkt).ThenInclude(v => v!.Viapunktkluster).ThenInclude(v => v!.Standarddestineringar).ThenInclude(v => v.DestineringMottagningsplats).ThenInclude(s => s.Mottagningsplats)
.Include(d => d.Viapunkt).ThenInclude(v => v!.Viapunktkluster).ThenInclude(v => v!.Standarddestineringar).ThenInclude(v => v.DestineringSortiment).ThenInclude(s => s.ProduceratHandelssortiment)
.Include(d => d.Avlaggskvantiteter).ThenInclude(a => a.Avlagg)
.Include(d => d.Flodesomrade)
.Include(d => d.Ursprung)
.Include(d => d.Huggningsform)
.Include(d => d.Terrangbarighet)
.Include(d => d.Vagbarighet)
.Include(d => d.Arstid)
.Include(d => d.Traktplaneringsmetod)
.Include(d => d.Kommentarer)
.Include(d => d.Kommun)
.Include(d => d.LokaltTeam)
.Where(d => request.Flodesomraden.Contains(d.FlodesomradeId) && !d.Fardig)
.AsNoTracking()
.ToListAsync(cancellationToken);

Include stack traces

Include verbose output

Include provider and version information

EF Core version: 9.0.0
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 9.0
Operating system:
IDE: Visual Studio 2022 17.12.2

[ajcvickers]

Duplicate of #35053