CREATE TABLE `label` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT 'id',
  `name` varchar(190) COLLATE utf8mb4_unicode_ci DEFAULT 'label name',
  PRIMARY KEY (`id`),
  UNIQUE KEY `uniq_n` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=7050965 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='label'

const (
   // 最大字符長(zhǎng)度
   LabelNameLengthLimit = 190
)
func GetOrCreateLabel(ctx context.Context, name string) (label dao.Label, err error) {
   var err error
   // 依據(jù)name查詢label信息
   label, err = db_reader.GetLabel(name)
   // 沒(méi)有找到對(duì)應(yīng)的label信息，且字符串長(zhǎng)度超過(guò)190，則切片后再次查詢
   if IsRecordNotFoundError(err) && len(name) > LabelNameLengthLimit {
      label, err = db_reader.GetLabel(name[:LabelNameLengthLimit])
   }
   // 還是報(bào)錯(cuò)，則嘗試創(chuàng)建label信息
   if err != nil {
      label.Name = name
      err = db_writer.CreateLabel(ctx, &label)
      // 報(bào)唯一鍵沖突錯(cuò)誤，可能是由于并發(fā)創(chuàng)建導(dǎo)致的問(wèn)題，再次兜底進(jìn)行查詢
      if IsKeyConflict(err) {
         label, err = db_reader.GetLabel(ctx, name)
         if err != nil {
            return label, err
         }
      }
      if err != nil {
         return label, err
      }
   }
   return label, nil
}

labelName := "? 2015 Charanga Sí o Ké - Chema Mu?oz, Perfecto Artola, Pablo Guerrero, Antonio Flores, Los Gipsy King, Chambao, Adele, La Pegatina, El Chaval de la Peca, Los Manolos ? 2015 Charanga Sí o Ké - Sones de Rumba"

var err error
// 依據(jù)name查詢label信息
label, err = db_reader.GetLabel(name)
// 沒(méi)有找到對(duì)應(yīng)的label信息，且字符串長(zhǎng)度超過(guò)190，則切片后再次查詢
if IsRecordNotFoundError(err) && len(name) > LabelNameLengthLimit {
   label, err = db_reader.GetLabel(name[:LabelNameLengthLimit])
}

err = db_writer.CreateLabel(ctx, &label)
// 報(bào)唯一鍵沖突錯(cuò)誤，可能是由于并發(fā)創(chuàng)建導(dǎo)致的問(wèn)題，再次兜底進(jìn)行查詢
if IsKeyConflict(err) {
   label, err = db_reader.GetLabel(ctx, name)
   if err != nil {
      return label, err
   }
}

// StringHeader is the runtime representation of a string.
// It cannot be used safely or portably and its representation may
// change in a later release.
// Moreover, the Data field is not sufficient to guarantee the data
// it references will not be garbage collected, so programs must keep
// a separate, correctly typed pointer to the underlying data.
type StringHeader struct {
   Data uintptr
   Len  int
}

labelName := "? 2015 Charanga Sí o Ké - Chema Mu?oz, Perfecto Artola, Pablo Guerrero, Antonio Flores, Los Gipsy King, Chambao, Adele, La Pegatina, El Chaval de la Peca, Los Manolos ? 2015 Charanga Sí o Ké - Sones de Rumba"
fmt.Println("原字符串內(nèi)容：", labelName)
fmt.Println("字節(jié)長(zhǎng)度：", len(labelName))
fmt.Println("按照字節(jié)截取內(nèi)容：", labelName[:LabelNameLengthLimit])
fmt.Println("字符長(zhǎng)度：", len([]rune(labelName)))
fmt.Println("按照字符截取內(nèi)容：", string([]rune(labelName)[:LabelNameLengthLimit]))

const (
   // 最大字符長(zhǎng)度
   LabelNameLengthLimit = 190
)
func GetOrCreateLabel(ctx context.Context, name string) (label dao.Label, err error) {
   if rs := []rune(name); len(rs) > LabelNameLengthLimit {
      name = string(rs[:LabelNameLengthLimit])
   }
   var err error
   // 依據(jù)name查詢label信息
   label, err = db_reader.GetLabel(name)
   // 還是報(bào)錯(cuò)，則嘗試創(chuàng)建label信息
   if err != nil {
      label.Name = name
      err = db_writer.CreateLabel(ctx, &label)
      // 報(bào)唯一鍵沖突錯(cuò)誤，可能是由于并發(fā)創(chuàng)建導(dǎo)致的問(wèn)題，再次兜底進(jìn)行查詢
      if IsKeyConflict(err) {
         label, err = db_reader.GetLabel(ctx, name)
         if err != nil {
            return label, err
         }
      }
      if err != nil {
         return label, err
      }
   }
   return label, nil
}