Added better Insert skip check.

Author: sdanyliv

Source/LinqToDB.EntityFrameworkCore/EFCoreMetadataReader.cs

@@ -259,6 +259,17 @@ public T[] GetAttributes<T>(Type type, MemberInfo memberInfo, bool inherit = tru
 							}
 						}
 
+						var behaviour = prop.BeforeSaveBehavior;
+						var skipOnInsert = prop.ValueGenerated.HasFlag(ValueGenerated.OnAdd);
+
+						if (skipOnInsert)
+						{
+							skipOnInsert = isIdentity || behaviour != PropertySaveBehavior.Save;
+						}
+
+						var skipOnUpdate = behaviour != PropertySaveBehavior.Save ||
+						                   prop.ValueGenerated.HasFlag(ValueGenerated.OnUpdate);
+
 						return new T[]
 						{
 							(T)(Attribute)new ColumnAttribute
@@ -271,7 +282,9 @@ public T[] GetAttributes<T>(Type type, MemberInfo memberInfo, bool inherit = tru
 								IsPrimaryKey    = isPrimaryKey,
 								PrimaryKeyOrder = primaryKeyOrder,
 								IsIdentity      = isIdentity,
-								IsDiscriminator = discriminator == prop
+								IsDiscriminator = discriminator == prop,
+								SkipOnInsert    = skipOnInsert,
+								SkipOnUpdate    = skipOnUpdate
 							}
 						};
 					}

Tests/LinqToDB.EntityFrameworkCore.PostgreSQL.Tests/Models/NpgSqlEntities/EntityWithXmin.cs

@@ -0,0 +1,14 @@
+using System;
+using System.ComponentModel.DataAnnotations;
+
+namespace LinqToDB.EntityFrameworkCore.PostgreSQL.Tests.Models.NpgSqlEntities
+{
+	public class EntityWithXmin
+	{
+		[Key]
+		public int Id { get; set; }
+
+		public uint xmin { get; set; }
+		public string Value { get; set; } = null!;
+	}
+}

Tests/LinqToDB.EntityFrameworkCore.PostgreSQL.Tests/Models/NpgSqlEntities/NpgSqlEnititesContext.cs

@@ -26,10 +26,17 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
 			modelBuilder.Entity<EntityWithArrays>(entity =>
 			{
 			});
+
+			modelBuilder.Entity<EntityWithXmin>(entity =>
+			{
+				entity.ForNpgsqlUseXminAsConcurrencyToken();
+			});
+
 		}
 
 		public virtual DbSet<Event> Events { get; set; } = null!;
 		public virtual DbSet<EntityWithArrays> EntityWithArrays { get; set; } = null!;
+		public virtual DbSet<EntityWithXmin> EntityWithXmin { get; set; } = null!;
 
 	}
 }