千家信息网

请输入关键字词

热门搜索排行

最新搜索排行

导航： 首页 > 数据库 >

MongoDB中索引怎么用

发表于：2024-11-11 作者：千家信息网编辑
千家信息网最后更新 2024年11月11日，小编给大家分享一下MongoDB中索引怎么用，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！在任何数据库之中，索引都是一种提
千家信息网最后更新 2024年11月11日MongoDB中索引怎么用

小编给大家分享一下MongoDB中索引怎么用，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

在任何数据库之中，索引都是一种提升数据库检索性能的手段。
MongoDB数据库里面依然会存在两种索引创建：一种是自动创建，另外一种是手工创建。

范例：重新准备一个新的简单集合。
db.emp.drop();
db.emp.insert({"name":"赵一","sex":"男","age":30,"sal":1000,"loc":"北京"});
db.emp.insert({"name":"钱二","sex":"女","age":22,"sal":5000,"loc":"上海"});
db.emp.insert({"name":"孙三","sex":"男","age":40,"sal":2000,"loc":"深圳"});
db.emp.insert({"name":"李四","sex":"女","age":30,"sal":7000,"loc":"北京"});
db.emp.insert({"name":"周五","sex":"女","age":30,"sal":6400,"loc":"北京"});
db.emp.insert({"name":"吴六","sex":"男","age":30,"sal":2500,"loc":"重庆"});
db.emp.insert({"name":"郑七","sex":"女","age":50,"sal":4700,"loc":"成都"});
db.emp.insert({"name":"王八","sex":"男","age":35,"sal":8000,"loc":"北京"});

此时在emp的集合上并没有去设置任何的索引，可以通过getIndexes()函数来观察在emp集合中的索引。

范例：查询默认状态下emp集合的索引内容
> db.emp.getIndexes();
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "hr.emp"
}
]

现在发现会存在有一个"_id"列的索引内容。但是如果要想创建自己的索引，则可以使用如下的语法：
索引创建：db.集合名称.createIndex({列:1})
设置的1表示索引按照升序的方式进行排序，如果使用降序则使用"-1"

范例：创建一个索引，在age字段上设置一个降序索引
> db.emp.createIndex({"age":-1})
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
此时并没有设置索引的名字，所以名字是自动命名的。命名的规范："字段名称_索引的排序模式"
> db.emp.getIndexes();
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "hr.emp"
},
{
"v" : 2,
"key" : {
"age" : -1
},
"name" : "age_-1",
"ns" : "hr.emp"
}
]

范例：针对于当前的age字段上的索引做一个分析
> db.emp.find({"age":30}).explain("executionStats");
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "hr.emp",
"indexFilterSet" : false,
"parsedQuery" : {
"age" : {
"$eq" : 30
}
},
"winningPlan" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"age" : -1
},
"indexName" : "age_-1",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
]
}
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 4,
"executionTimeMillis" : 0,
"totalKeysExamined" : 4,
"totalDocsExamined" : 4,
"executionStages" : {
"stage" : "FETCH",
"nReturned" : 4,
"executionTimeMillisEstimate" : 0,
"works" : 5,
"advanced" : 4,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 4,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 4,
"executionTimeMillisEstimate" : 0,
"works" : 5,
"advanced" : 4,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"age" : -1
},
"indexName" : "age_-1",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
]
},
"keysExamined" : 4,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
"serverInfo" : {
"host" : "D2-LZY245",
"port" : 27017,
"version" : "3.4.7",
"gitVersion" : "cf38c1b8a0a8dca4a11737581beafef4fe120bcd"
},
"ok" : 1
}

此时的查询使用了索引的技术，但是下面再来观察一个查询，不使用索引字段

范例：针对于sal字段进行查询
> db.emp.find({"sal":{"$gt":5000}}).explain("executionStats");
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "hr.emp",
"indexFilterSet" : false,
"parsedQuery" : {
"sal" : {
"$gt" : 5000
}
},
"winningPlan" : {
"stage" : "COLLSCAN",
"filter" : {
"sal" : {
"$gt" : 5000
}
},
"direction" : "forward"
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 3,
"executionTimeMillis" : 0,
"totalKeysExamined" : 0,
"totalDocsExamined" : 8,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"sal" : {
"$gt" : 5000
}
},
"nReturned" : 3,
"executionTimeMillisEstimate" : 0,
"works" : 10,
"advanced" : 3,
"needTime" : 6,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 8
}
},
"serverInfo" : {
"host" : "D2-LZY245",
"port" : 27017,
"version" : "3.4.7",
"gitVersion" : "cf38c1b8a0a8dca4a11737581beafef4fe120bcd"
},
"ok" : 1
}
此时在sal字段上并没有设置索引，所以当前的索引形式就变成了全集合扫描的模式。
但是如果说，现在换一种形式，年龄和薪水一起执行查询：
> db.emp.find({"age":30,"sal":7000}).explain("executionStats")
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "hr.emp",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"age" : {
"$eq" : 30
}
},
{
"sal" : {
"$eq" : 7000
}
}
]
},
"winningPlan" : {
"stage" : "FETCH",
"filter" : {
"sal" : {
"$eq" : 7000
}
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"age" : -1
},
"indexName" : "age_-1",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
]
}
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 0,
"totalKeysExamined" : 4,
"totalDocsExamined" : 4,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"sal" : {
"$eq" : 7000
}
},
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 5,
"advanced" : 1,
"needTime" : 3,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 4,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 4,
"executionTimeMillisEstimate" : 0,
"works" : 5,
"advanced" : 4,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"age" : -1
},
"indexName" : "age_-1",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
]
},
"keysExamined" : 4,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
"serverInfo" : {
"host" : "D2-LZY245",
"port" : 27017,
"version" : "3.4.7",
"gitVersion" : "cf38c1b8a0a8dca4a11737581beafef4fe120bcd"
},
"ok" : 1
}
这个时候虽然age字段上面存在索引，由于sal字段上面没有索引，所以依然使用的是全表扫描操作。为了解决此时的问题，可以使用一个复合索引。
> db.emp.createIndex({"age":-1,"sal":-1},{name:"age_-1_sal_-1_index"})
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 2,
"numIndexesAfter" : 3,
"ok" : 1
}

范例：默认使用索引
> db.emp.find({"age":30,"sal":7000}).explain("executionStats")
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "hr.emp",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"age" : {
"$eq" : 30
}
},
{
"sal" : {
"$eq" : 7000
}
}
]
},
"winningPlan" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"age" : -1,
"sal" : -1
},
"indexName" : "age_-1_sal_-1_index",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ],
"sal" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
],
"sal" : [
"[7000.0, 7000.0]"
]
}
}
},
"rejectedPlans" : [
{
"stage" : "FETCH",
"filter" : {
"sal" : {
"$eq" : 7000
}
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"age" : -1
},
"indexName" : "age_-1",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
]
}
}
}
]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 0,
"totalKeysExamined" : 1,
"totalDocsExamined" : 1,
"executionStages" : {
"stage" : "FETCH",
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 3,
"advanced" : 1,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 1,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 2,
"advanced" : 1,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"age" : -1,
"sal" : -1
},
"indexName" : "age_-1_sal_-1_index",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ],
"sal" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[30.0, 30.0]"
],
"sal" : [
"[7000.0, 7000.0]"
]
},
"keysExamined" : 1,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
"serverInfo" : {
"host" : "D2-LZY245",
"port" : 27017,
"version" : "3.4.7",
"gitVersion" : "cf38c1b8a0a8dca4a11737581beafef4fe120bcd"
},
"ok" : 1
}

但是如果换到了以下条件：
> db.emp.find({"$or":[{"age":{"$gt":30}},{"sal":{"$gt":5000}}]}).explain("executionStats")
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "hr.emp",
"indexFilterSet" : false,
"parsedQuery" : {
"$or" : [
{
"age" : {
"$gt" : 30
}
},
{
"sal" : {
"$gt" : 5000
}
}
]
},
"winningPlan" : {
"stage" : "SUBPLAN",
"inputStage" : {
"stage" : "COLLSCAN",
"filter" : {
"$or" : [
{
"age" : {
"$gt" : 30
}
},
{
"sal" : {
"$gt" : 5000
}
}
]
},
"direction" : "forward"
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 5,
"executionTimeMillis" : 0,
"totalKeysExamined" : 0,
"totalDocsExamined" : 8,
"executionStages" : {
"stage" : "SUBPLAN",
"nReturned" : 5,
"executionTimeMillisEstimate" : 0,
"works" : 10,
"advanced" : 5,
"needTime" : 4,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"inputStage" : {
"stage" : "COLLSCAN",
"filter" : {
"$or" : [
{
"age" : {
"$gt" : 30
}
},
{
"sal" : {
"$gt" : 5000
}
}
]
},
"nReturned" : 5,
"executionTimeMillisEstimate" : 0,
"works" : 10,
"advanced" : 5,
"needTime" : 4,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 8
}
}
},
"serverInfo" : {
"host" : "D2-LZY245",
"port" : 27017,
"version" : "3.4.7",
"gitVersion" : "cf38c1b8a0a8dca4a11737581beafef4fe120bcd"
},
"ok" : 1
}

现在发现并没有使用索引，所以这个时候看能否强制使用一次索引：hint()函数为强制使用索引操作。
范例：强制使用索引
> db.emp.find({"$or":[{"age":{"$gt":50}},{"sal":{"$gt":3000}}]}).hint("age_-1_sal_-1_index").explain("executionStats")
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "hr.emp",
"indexFilterSet" : false,
"parsedQuery" : {
"$or" : [
{
"age" : {
"$gt" : 50
}
},
{
"sal" : {
"$gt" : 3000
}
}
]
},
"winningPlan" : {
"stage" : "FETCH",
"filter" : {
"$or" : [
{
"age" : {
"$gt" : 50
}
},
{
"sal" : {
"$gt" : 3000
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"age" : -1,
"sal" : -1
},
"indexName" : "age_-1_sal_-1_index",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ],
"sal" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[MaxKey, MinKey]"
],
"sal" : [
"[MaxKey, MinKey]"
]
}
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 5,
"executionTimeMillis" : 0,
"totalKeysExamined" : 8,
"totalDocsExamined" : 8,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"$or" : [
{
"age" : {
"$gt" : 50
}
},
{
"sal" : {
"$gt" : 3000
}
}
]
},
"nReturned" : 5,
"executionTimeMillisEstimate" : 0,
"works" : 9,
"advanced" : 5,
"needTime" : 3,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 8,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 8,
"executionTimeMillisEstimate" : 0,
"works" : 9,
"advanced" : 8,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"age" : -1,
"sal" : -1
},
"indexName" : "age_-1_sal_-1_index",
"isMultiKey" : false,
"multiKeyPaths" : {
"age" : [ ],
"sal" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"age" : [
"[MaxKey, MinKey]"
],
"sal" : [
"[MaxKey, MinKey]"
]
},
"keysExamined" : 8,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
"serverInfo" : {
"host" : "D2-LZY245",
"port" : 27017,
"version" : "3.4.7",
"gitVersion" : "cf38c1b8a0a8dca4a11737581beafef4fe120bcd"
},
"ok" : 1
}

如果正常来讲，这个代码根本就不可能调用默认的索引执行，如果需要可以使用hint()函数强制MongoDB必须使用索引。
如果在一个集合里面设置了过多的索引，实际上会导致性能下降。那么可以删除索引。

范例：删除一个索引
> db.emp.dropIndex("age_-1_sal_-1_index")
{ "nIndexesWas" : 3, "ok" : 1 }
> db.emp.getIndexes();
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "hr.emp"
},
{
"v" : 2,
"key" : {
"age" : -1
},
"name" : "age_-1",
"ns" : "hr.emp"
}
]

范例：删除非"_id"的索引，也就是自定义的索引
> db.emp.dropIndexes();
{
"nIndexesWas" : 2,
"msg" : "non-_id indexes dropped for collection",
"ok" : 1
}
> db.emp.getIndexes();
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "hr.emp"
}
]
以上是"MongoDB中索引怎么用"这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注行业资讯频道！

很赞哦！
索引 范例 字段 查询 内容 北京 强制 函数 数据 数据库 篇文章 名字 名称 形式 性能 时候 模式 排序 观察 不怎么 数据库的安全要保护哪些东西 数据库安全各自的含义是什么 生产安全数据库录入 数据库的安全性及管理 数据库安全策略包含哪些 海淀数据库安全审计系统 建立农村房屋安全信息数据库 易用的数据库客户端支持安全管理 连接数据库失败ssl安全错误 数据库的锁怎样保障安全 计算机网络技术都有哪些技术 本地服务器的搭建 hdfs的服务器 滁州机架式服务器哪家好 全国网络安全 会议 鼎墨扬州互联网科技有限公司 盐城服务器价格 无锡光学系统设计软件开发 软件开发者会遇到的风险 开平区专业性软件开发 服务器系统怎么挂游戏 疫情防控期间网络安全保障 山东有网络安全专业的大学吗 2016的服务器选择 数组循环写入数据库 昌平区数据网络技术质量保证 h5 请求后端服务器原理 永恒之塔怀旧服选了服务器 湖南诺源互联网科技 文旅局网络安全和信息化工作 赛门铁克 服务器备份 天津静海网络安全副队长 西安互联网科技有限公司 昆明服务器云存储价格 软件开发预算报价 mysql数据库在哪里建立 苹果手机天气服务器崩溃 恩度网络技术有限公司 腾讯云服务器到期了多久释放 17年国赛网络安全

相关文章

0