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云开发环境，数据库丢失什么原因，如何恢复

// 云函数入口文件 const cloud = require('wx-server-sdk') const xlsx = require('node-xlsx') cloud.init({   env: cloud.DYNAMIC_CURRENT_ENV }) // 云函数入口函数excel 操作 exports.main = async (event, context) => {   const db = cloud.database()   // console.log("进入云函数",event)   //通过fileId下载云存储里的文件   const excelres  = await cloud.downloadFile({     fileID :  event.fileId   })   const  buffer = excelres.fileContent   const tasks = []  //用来存储所有等添加数据操作   //解析excel文件里等数据   var sheets = xlsx.parse(buffer);//获取到所有sheets   sheets.forEach(function(sheet){     for (var rowId= 0 ; rowId < sheet['data'].length ; rowId++){       var row = sheet['data'][rowId];//第几行数据       console.log("当前行",rowId,row)        if (rowId > 0 && row){         let options = ""         let optionsOrde = ['A','B','C','D','E','F']         let answer = ''         let ishad = ''         //重复的题目不再添加         db.collection('question').where({           title:row[0].trim()         }).count().then((res1)=>{                      console.log(res1)           if(res1.total === 0){             console.log('new',rowId)             //选项 str {{key:A,val=answerA},{key:B,val=answerB}}            for(let i= 1;i <= 5;i++){                 if(row[i]){                    let str =row[i].toString()                    // console.log(typeof(str))                    str = str.replace(/(^\s*)|(\s*$)/g, '')                    options = options + "{\"key\":\""  + optionsOrde[i-1] + "\",\"val\"" + ":" + "\"" + str + "\"}" + ","                }            }                   //在数据库中插入数据            options = options.replace(/(^\s*)|(\s*$)/g, '');             options = options.trim()             answer = answer.trim()             const promise = db.collection('question').add({                 data: {                   title:row[0].trim(),                   options:"{\"optionlist\":[" + options.substring(0,options.length-1) + "]}",                   answer:row[8].trim(),                   type:row[7],                   course:row[6],                   create_date:db.serverDate()                 }             }).then((res) =>{               if(res.data._id){                 tasks.push(promise)               }             }).catch(function(err) {               return err             })           }           return tasks         })         .catch(function(err) {           return err         })                         }     }   });   let result = tasks.reduce((prev,next)=>prev.then(()=>next()),Promise.resolve())   result.then(res1 => {     return res1   })   //return result }