executor: only rebase auto increment ID when needed

executor/write.go

@@ -71,27 +71,27 @@ func updateRecord(ctx sessionctx.Context, h int64, oldData, newData []types.Datu
 				return false, handleChanged, newHandle, errors.Trace(err)
 			}
 		}
-		// Rebase auto increment id if the field is changed.
-		if mysql.HasAutoIncrementFlag(col.Flag) {
-			if newData[i].IsNull() {
-				return false, handleChanged, newHandle, table.ErrColumnCantNull.GenByArgs(col.Name)
-			}
-			val, errTI := newData[i].ToInt64(sc)
-			if errTI != nil {
-				return false, handleChanged, newHandle, errors.Trace(errTI)
-			}
-			err := t.RebaseAutoID(ctx, val, true)
-			if err != nil {
-				return false, handleChanged, newHandle, errors.Trace(err)
-			}
-		}
 		cmp, err := newData[i].CompareDatum(sc, &oldData[i])
 		if err != nil {
 			return false, handleChanged, newHandle, errors.Trace(err)
 		}
 		if cmp != 0 {
 			changed = true
 			modified[i] = true
+			// Rebase auto increment id if the field is changed.
+			if mysql.HasAutoIncrementFlag(col.Flag) {
+				if newData[i].IsNull() {
+					return false, handleChanged, newHandle, table.ErrColumnCantNull.GenByArgs(col.Name)
+				}
+				val, errTI := newData[i].ToInt64(sc)
+				if errTI != nil {
+					return false, handleChanged, newHandle, errors.Trace(errTI)
+				}
+				err := t.RebaseAutoID(ctx, val, true)
+				if err != nil {
+					return false, handleChanged, newHandle, errors.Trace(err)
+				}
+			}
 			if col.IsPKHandleColumn(t.Meta()) {
 				handleChanged = true
 				newHandle = newData[i].GetInt64()

executor/write_test.go

@@ -2021,3 +2021,36 @@ func (s *testSuite) TestReplaceLog(c *C) {
 
 	tk.MustQuery(`admin cleanup index testLog b;`).Check(testkit.Rows("1"))
 }
+
+// For issue 7422.
+// There is no need to do the rebase when updating a record if the auto-increment ID not changed.
+// This could make the auto ID increasing speed slower.
+func (s *testSuite) TestRebaseIfNeeded(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec(`create table t (a int not null primary key auto_increment, b int unique key);`)
+	tk.MustExec(`insert into t (b) values (1);`)
+
+	s.ctx = mock.NewContext()
+	s.ctx.Store = s.store
+	tbl, err := s.domain.InfoSchema().TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
+	c.Assert(err, IsNil)
+	c.Assert(s.ctx.NewTxn(), IsNil)
+	// AddRecord directly here will skip to rebase the auto ID in the insert statement,
+	// which could simulate another TiDB adds a large auto ID.
+	_, err = tbl.AddRecord(s.ctx, types.MakeDatums(30001, 2), false)
+	c.Assert(err, IsNil)
+	c.Assert(s.ctx.Txn().Commit(context.Background()), IsNil)
+
+	tk.MustExec(`update t set b = 3 where a = 30001;`)
+	tk.MustExec(`insert into t (b) values (4);`)
+	tk.MustQuery(`select a from t where b = 4;`).Check(testkit.Rows("2"))
+
+	tk.MustExec(`insert into t set b = 3 on duplicate key update a = a;`)
+	tk.MustExec(`insert into t (b) values (5);`)
+	tk.MustQuery(`select a from t where b = 5;`).Check(testkit.Rows("4"))
+
+	tk.MustExec(`insert into t set b = 3 on duplicate key update a = a + 1;`)
+	tk.MustExec(`insert into t (b) values (6);`)
+	tk.MustQuery(`select a from t where b = 6;`).Check(testkit.Rows("30003"))
+}