func removeOnUpdateNowFlag(c *column.Col) {
	// For timestamp Col, if it is set null or default value,
	// OnUpdateNowFlag should be removed.
	if mysql.HasTimestampFlag(c.Flag) {
		c.Flag &= ^uint(mysql.OnUpdateNowFlag)
	}
}

func setNoDefaultValueFlag(c *column.Col, hasDefaultValue bool) {
	if hasDefaultValue {
		return
	}

	if !mysql.HasNotNullFlag(c.Flag) {
		return
	}

	// Check if it is an `AUTO_INCREMENT` field or `TIMESTAMP` field.
	if !mysql.HasAutoIncrementFlag(c.Flag) && !mysql.HasTimestampFlag(c.Flag) {
		c.Flag |= mysql.NoDefaultValueFlag
	}
}

func setTimestampDefaultValue(c *column.Col, hasDefaultValue bool, setOnUpdateNow bool) {
	if hasDefaultValue {
		return
	}

	// For timestamp Col, if is not set default value or not set null, use current timestamp.
	if mysql.HasTimestampFlag(c.Flag) && mysql.HasNotNullFlag(c.Flag) {
		if setOnUpdateNow {
			c.DefaultValue = expressions.ZeroTimestamp
		} else {
			c.DefaultValue = expressions.CurrentTimestamp
		}
	}
}

func (s *InsertIntoStmt) initDefaultValues(ctx context.Context, t table.Table, cols []*column.Col, row []interface{}, marked map[int]struct{}) error {
	var err error
	var defaultValueCols []*column.Col
	for i, c := range cols {
		if row[i] != nil {
			// Column value is not nil, continue.
			continue
		}

		// If the nil value is evaluated in insert list, we will use nil except auto increment column.
		if _, ok := marked[i]; ok && !mysql.HasAutoIncrementFlag(c.Flag) && !mysql.HasTimestampFlag(c.Flag) {
			continue
		}

		if mysql.HasAutoIncrementFlag(c.Flag) {
			var id int64
			if id, err = t.AllocAutoID(); err != nil {
				return errors.Trace(err)
			}
			row[i] = id
			variable.GetSessionVars(ctx).SetLastInsertID(uint64(id))
		} else {
			var value interface{}
			value, _, err = getDefaultValue(ctx, c)
			if err != nil {
				return errors.Trace(err)
			}

			row[i] = value
		}

		defaultValueCols = append(defaultValueCols, c)
	}

	if err = column.CastValues(ctx, row, defaultValueCols); err != nil {
		return errors.Trace(err)
	}

	return nil
}