Merge pull request #94 from Giorgi/claude/investigate-deadlock-CT6ly

Add IsDeadlockError

Author: Giorgi

EntityFramework.Exceptions/Tests/OracleTests.cs

@@ -1,4 +1,6 @@
-using System.Threading.Tasks;
+using System.Linq;
+using System.Threading.Tasks;
+using EntityFramework.Exceptions.Common;
 using EntityFramework.Exceptions.Oracle;
 using Microsoft.EntityFrameworkCore;
 using Testcontainers.Oracle;
@@ -12,10 +14,51 @@ public OracleTests(OracleTestContextFixture fixture) : base(fixture.DemoContext)
     {
     }
 
-    [Fact(Skip = "Skipping as oracle can't trigger deadlock.")]
-    public override Task Deadlock()
+    [Fact]
+    public override async Task Deadlock()
     {
-        return Task.CompletedTask;
+        var p1 = DemoContext.Products.Add(new() { Name = "Test1" });
+        var p2 = DemoContext.Products.Add(new() { Name = "Test2" });
+        await DemoContext.SaveChangesAsync();
+
+        var id1 = p1.Entity.Id;
+        var id2 = p2.Entity.Id;
+
+        await using var controlContext = new DemoContext(DemoContext.Options);
+        await using var transaction1 = await DemoContext.Database.BeginTransactionAsync();
+        await using var transaction2 = await controlContext.Database.BeginTransactionAsync();
+
+        // Each transaction locks one row
+        await DemoContext.Products.Where(c => c.Id == id1)
+            .ExecuteUpdateAsync(c => c.SetProperty(p => p.Name, "Test11"));
+        await controlContext.Products.Where(c => c.Id == id2)
+            .ExecuteUpdateAsync(c => c.SetProperty(p => p.Name, "Test21"));
+
+        // Start both cross-updates concurrently to create a deadlock cycle
+        var task1 = Task.Run(() => DemoContext.Products
+            .Where(c => c.Id == id2)
+            .ExecuteUpdateAsync(c => c.SetProperty(p => p.Name, "Test22")));
+        var task2 = Task.Run(() => controlContext.Products
+            .Where(c => c.Id == id1)
+            .ExecuteUpdateAsync(c => c.SetProperty(p => p.Name, "Test12")));
+
+        // Oracle only rolls back the victim's statement, not its transaction,
+        // so the non-victim remains blocked. Use WhenAny to catch the victim first.
+        var completedTask = await Task.WhenAny(task1, task2);
+        await Assert.ThrowsAsync<DeadlockException>(() => completedTask);
+
+        // Roll back the victim's transaction to release its earlier locks
+        // and unblock the other session.
+        if (completedTask == task1)
+        {
+            await transaction1.RollbackAsync();
+            await task2;
+        }
+        else
+        {
+            await transaction2.RollbackAsync();
+            await task1;
+        }
     }
 }