错误案例 Duplicate_idValues 如果_id值不是全局唯一的,则重新分片操作会失败,以避免损坏集合数据。重复的_id值也会阻止成功的数据段迁移。如果您的文档具有重复的_id值,请将每个文档中的数据复制到新文档中,然后删除重复的文档。
sparse and unique Properties An index that is both sparse and unique prevents collection from having documents with duplicate values for a field but allows multiple documents that omit the key.例子 在A集合上创建稀疏索引 Consider a collection scores that contains the following documents: { "_id" ...
db.students.find({"age":19}).explain();{"queryPlanner":{"plannerVersion":1,"namespace":"mldn.students","indexFilterSet":false,"parsedQuery":{"age":{"$eq":19}},"winningPlan":{"stage":"FETCH","inputStage":{"stage":"IXSCAN","keyPattern":{"age":-1},"indexName":"age_-1","i...
//创建唯一索引:如果数据重复将会报错 //com.mongodb.MongoException$DuplicateKey: E11000 duplicate key error index: sample.user.$age_name_index dup key collection.ensureIndex(new BasicDBObject("age", -1).append("username", 1), "age_name_index", true); //根据索引名称删除 collection.dropIndex...
说明: 若插入的数据主键已经存在,则会抛 org.springframework.dao.DuplicateKeyException 异常,提示主键重复,不保存当前数据。 案例: 如向集合user_demo中插入一条数据: db.user_demo.insert({"name":"zhangsan","age":18})# 相当于sql中的insert into user_demo(name, age) values("zhangsan",18); ...
When sorting on a field which contains duplicate values, documents containing those values may be returned in any order. If consistent sort order is desired, include at least one field in your sort that contains unique values. The easiest way to guarantee this is to include the _id field in...
db.movie.find() > db.movie.insert({"_id":08001,"name":"lisi"}) WriteResult({ "nInserted" : 0, "writeError" : { "code" : 11000, "errmsg" : "E11000 duplicate key error collection: mydb.movie index: _id_ dup key: { : 8001.0 }" ...
1、用deb安装的,会在 /etc 目录下 创建mongodb.conf (若没自动创建,可以自己创建),这是默认的配置文件,可以配置默认的 dbpath 路径等。 2、若是用的解压版,则即使在 /etc 目录创建 mongodb.conf 文件也无效,只有在命令行用--dbpath/Volumes/Data/mongodb指定。或者用-f/path/to/mongodb.conf 指定配置文件...
insert(): 若插入的数据主键已经存在,则会抛 org.springframework.dao.DuplicateKeyException 异常,提示主键重复,不保存当前数据。 3.2 版本之后新增了 db.collection.insertOne() 和 db.collection.insertMany()。 db.collection.insertOne() 用于向集合插入一个新文档,语法格式如下: ...
//com.mongodb.MongoException$DuplicateKey: E11000 duplicate key error index: sample.user.$age_name_index dup key collection.ensureIndex(new BasicDBObject("age", -1).append("username", 1), "age_name_index", true); //根据索引名称删除 ...