Add a way for providers to filter out non-identity conditions.

src/EFCore.Relational/Update/UpdateSqlGenerator.cs

@@ -6,6 +6,7 @@
 using System.Linq;
 using System.Text;
 using Microsoft.EntityFrameworkCore.Diagnostics;
+using Microsoft.EntityFrameworkCore.Metadata;
 using Microsoft.EntityFrameworkCore.Storage;
 using Microsoft.EntityFrameworkCore.Utilities;
 using Microsoft.Extensions.DependencyInjection;
@@ -499,19 +500,32 @@ protected virtual void AppendWhereAffectedClause(
                         {
                             if (v.IsKey)
                             {
-                                if (v.IsRead)
-                                {
-                                    AppendIdentityWhereCondition(sb, v);
-                                }
-                                else
+                                if (!v.IsRead)
                                 {
                                     AppendWhereCondition(sb, v, v.UseOriginalValueParameter);
+                                    return true;
                                 }
                             }
+
+                            if (IsIdentityOperation(v))
+                            {
+                                AppendIdentityWhereCondition(sb, v);
+                                return true;
+                            }
+
+                            return false;
                         }, " AND ");
             }
         }
 
+        /// <summary>
+        ///     Returns a value indicating whether the given modification represents an auto-incrementing column.
+        /// </summary>
+        /// <param name="modification"> The column modification. </param>
+        /// <returns> <see langword="true" /> if the given modification represents an auto-incrementing column. </returns>
+        protected virtual bool IsIdentityOperation(IColumnModification modification)
+            => modification.IsKey && modification.IsRead;
+
         /// <summary>
         ///     Appends a <c>WHERE</c> condition checking rows affected.
         /// </summary>

src/EFCore.SqlServer/Update/Internal/SqlServerUpdateSqlGenerator.cs

@@ -295,10 +295,10 @@ private void AppendMergeCommandHeader(
                 .Append('(')
                 .AppendJoin(
                     writeOperations,
-                    toInsertTableAlias,
-                    SqlGenerationHelper,
-                    (sb, o, alias, helper) =>
+                    (toInsertTableAlias, SqlGenerationHelper),
+                    static (sb, o, state) =>
                     {
+                        var (alias, helper) = state;
                         sb.Append(alias).Append('.');
                         helper.DelimitIdentifier(sb, o.ColumnName);
                     })

src/Shared/StringBuilderExtensions.cs

@@ -45,20 +45,21 @@ public static StringBuilder AppendJoin<T>(
             return stringBuilder;
         }
 
-        public static StringBuilder AppendJoin<T, TParam>(
+        public static StringBuilder AppendJoin<T>(
             this StringBuilder stringBuilder,
             IEnumerable<T> values,
-            TParam param,
-            Action<StringBuilder, T, TParam> joinAction,
+            Func<StringBuilder, T, bool> joinFunc,
             string separator = ", ")
         {
             var appended = false;
 
             foreach (var value in values)
             {
-                joinAction(stringBuilder, value, param);
-                stringBuilder.Append(separator);
-                appended = true;
+                if (joinFunc(stringBuilder, value))
+                {
+                    stringBuilder.Append(separator);
+                    appended = true;
+                }
             }
 
             if (appended)
@@ -69,19 +70,18 @@ public static StringBuilder AppendJoin<T, TParam>(
             return stringBuilder;
         }
 
-        public static StringBuilder AppendJoin<T, TParam1, TParam2>(
+        public static StringBuilder AppendJoin<T, TParam>(
             this StringBuilder stringBuilder,
             IEnumerable<T> values,
-            TParam1 param1,
-            TParam2 param2,
-            Action<StringBuilder, T, TParam1, TParam2> joinAction,
+            TParam param,
+            Action<StringBuilder, T, TParam> joinAction,
             string separator = ", ")
         {
             var appended = false;
 
             foreach (var value in values)
             {
-                joinAction(stringBuilder, value, param1, param2);
+                joinAction(stringBuilder, value, param);
                 stringBuilder.Append(separator);
                 appended = true;
             }