HierarchyId GetHashCode Method returns a limited set of values #3636
Description
Bug description
Having upgraded my project from .NET Framework to .Net 8, and moving to EFCore, I encountered a drastic downturn in performance of client side queries and dictionaries involving HierarchyId.
On investigation I found that the HierarchyId GetHashCode method is providing hash values of only 0-255 (i.e. it is only using the first byte of the 32-bit integer).
This method refers to the GetHashCode method from Microsoft.SqlServer.Types.SqlHierarchyId, so the problem originates there.
The code snippet demonstrates the values for a small test case (all output values are between 0-255).
Your code
using Microsoft.EntityFrameworkCore;
HierarchyId[] hidArray =
[
HierarchyId.GetRoot()
, HierarchyId.Parse(@"/1/1/")
, HierarchyId.Parse(@"/1/2/3/1/")
, HierarchyId.Parse(@"/2/19/11/108/43/")
, HierarchyId.Parse(@"/44/12.5/721.23/1.1/")
, HierarchyId.Parse(@"/-32/19.1/93485/234/")
, HierarchyId.Parse(@"/407/")
, HierarchyId.Parse(@"/999999/1/1/1/")
, HierarchyId.Parse(@"/12/11/10/9/8/7/6/5/4/3/2/1/")
, HierarchyId.Parse(@"/-121/921873/564/2343/123/56/")
, HierarchyId.Parse(@"/99/98/97/")
, HierarchyId.Parse(@"/13/12/11/10/")
, HierarchyId.Parse(@"/2/4/6/8/")
, HierarchyId.Parse(@"/3/5/7/9/")
];
foreach(HierarchyId hid in hidArray)
{
int hc = hid.GetHashCode();
Console.WriteLine(hc.ToString());
}Stack traces
Verbose output
EF Core version
9.0.9
Database provider
No response
Target framework
No response
Operating system
No response
IDE
No response