JavaScript中MongoDB批量更新时无法同步打印控制台消息

批量更新数据库记录时，更新状态消息延迟到全部操作完成后才批量打印，而非逐条按迭代顺序输出。其中console.log('filter & up===> ', filter, upObj, serchKeyVal);能正常逐条打印，但数据库更新的成功/错误消息全部延迟输出。

原代码 #

const updateRecord = async (records, connObj) => {
  try{
    const isExistKey = records.some(obj => obj.hasOwnProperty(config.collectionKey));
    let collKey = config.collectionKey;
    console.log('collection key=========> ', isExistKey);
    if(isExistKey) {
      let updateCount = 1;
      for(let obj of records) {
        if(obj[collKey] && obj[collKey] === '') {
          console.log(`The search key value is missing for row ${updateCount} from the sheet.`);
        }else{
          let serchKeyVal = obj[collKey];
          let filter = {
            [collKey]: obj[collKey]
          }
          delete obj[collKey];
          let flag = Object.values(obj).every((v) => v !== '');
          if(!flag) {
            console.log(`Some of the values are missing for row ${updateCount} from sheet. So could not update.`);
          }else{
            const upObj = obj;
            console.log('filter & up===> ', filter, upObj, serchKeyVal);
            await connObj.collection(config.mongoCollection).updateOne(filter, { $set: upObj }, function (err, data) {
              if(err) {
                console.log(`Record could not updated with for ${serchKeyVal}`);
                console.log('Error while updating record====> ', err);
              }else{
                if(data.result.nModified === 1) {
                  console.log(`Record updated successfully for ${serchKeyVal}`);
                }else{
                  console.log(`No matched record/No new value to update for ${serchKeyVal}`);
                }
              }
            });
          }
        }
        updateCount++;
      }
    }else{
      console.log('The collection key is not found in csv sheet.');
    }
  }catch(error) {
    console.log('Error while updating records ===> ', error);
  }
}

问题原因 #

调用updateOne时传入了回调函数，此时MongoDB驱动会采用回调模式执行，不会返回Promise，导致await关键字无法等待异步操作完成。循环会直接快速遍历所有记录发起更新请求，而所有回调函数会在后续数据库操作完成后集中执行，因此状态消息会批量延迟输出。

解决方法 #

方法1：使用Promise版本的updateOne（推荐） #

移除回调函数，直接await驱动返回的Promise，这样循环会等待当前更新操作完成后再进入下一次迭代，确保消息按顺序输出：

// 替换原updateOne调用部分
const upObj = obj;
console.log('filter & up===> ', filter, upObj, serchKeyVal);
try {
  const data = await connObj.collection(config.mongoCollection).updateOne(filter, { $set: upObj });
  if(data.result.nModified === 1) {
    console.log(`Record updated successfully for ${serchKeyVal}`);
  } else {
    console.log(`No matched record/No new value to update for ${serchKeyVal}`);
  }
} catch (err) {
  console.log(`Record could not updated with for ${serchKeyVal}`);
  console.log('Error while updating record====> ', err);
}

方法2：将回调包装为Promise #

如果需要保留回调逻辑，可以手动将其包装为Promise，让await能够等待操作完成：

// 替换原updateOne调用部分
const upObj = obj;
console.log('filter & up===> ', filter, upObj, serchKeyVal);
await new Promise((resolve, reject) => {
  connObj.collection(config.mongoCollection).updateOne(filter, { $set: upObj }, function (err, data) {
    if(err) {
      console.log(`Record could not updated with for ${serchKeyVal}`);
      console.log('Error while updating record====> ', err);
      reject(err);
    } else {
      if(data.result.nModified === 1) {
        console.log(`Record updated successfully for ${serchKeyVal}`);
      } else {
        console.log(`No matched record/No new value to update for ${serchKeyVal}`);
      }
      resolve(data);
    }
  });
});

修改后，每次迭代都会等待当前数据库更新完成并打印状态后，再处理下一条记录，消息将按迭代顺序逐条输出。

内容的提问来源于stack exchange，提问作者subhra_user