mongodb常用查询语句

先将数据放入内存在排序(增大内存)
db.adminCommand({setParameter:1, internalQueryExecMaxBlockingSortBytes:335544320}) 

db.article_urls.count({"contentStatus":{$in:[-1,1,2,3,4]}})

db.article_urls.count({"contentStatus":0})

//contentStatus字段不存在的记录数
db.article_urls.count({"contentStatus":{$exists:false}})

//删除mid字段
db.wechat_article_content.update({},{$unset:{"mid":""}},false,true)

//将appMsgId字段修改为mid
db.wechat_article_content.update({}, {$rename : {"appMsgId" : "mid"}}, false, true)

//重命名
db.article_dynamic_data.update({},{$rename:{"likeAauthorImgs":"likeAuthorImgs"}},false,true);


//article_urls中contentStatus字段不存在的脏数据 
db.article_urls.updateMany({"contentStatus":{$exists:false}},{$set:{"contentStatus":NumberInt(0)}})

//创建索引
db.wechat_article_content.createIndex({"fetchTime":-1});
db.wechat_article_content.createIndex({"fetchTime":1});

db.TEST.totalIndexSize()

db.wechat_article_content.getIndexes()


db.wechat_article_comment.aggregate([
{$lookup:{from:'wechat_article_content',
  localField:'articleId',
  foreignField:'_id',
  as:'article'
  }},
  {$match:{"_id":"210514751111823373"}},
  {$project:{"_id":1,"nickName":1,"content":1,"article.title":1}}
  
])

{ 
    "_id" : "210514751111823373", 
    "nickName" : "苟小薇", 
    "content" : "现在的银行员工确实是在全意全意为客户着想", 
    "article" : [
        {
            "title" : "机警的银行柜员"
        }
    ]
}