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可以做推广的门户网站,免费外链代发平台,做外贸重新设计网站,现在的网站设计判断是否使用索引搜索索引在数据库中是一个不可或缺的存在，想让你的查询结果快准狠，还是需要索引的来帮忙，那么在mongo中如何判断搜索是不是走索引呢？通常使用执行计划（解释计划、Explain Plan）来查看查询…

判断是否使用索引搜索

索引在数据库中是一个不可或缺的存在，想让你的查询结果快准狠，还是需要索引的来帮忙，那么在mongo中如何判断搜索是不是走索引呢？通常使用执行计划（解释计划、Explain Plan）来查看查询的情况，如查询耗费的时间、是否基于索引查询等。

索引语法

db.collection.find(query,options).explain(options)

创建索引前

查看根据name查询数据的情况：

> db.user.find({"name":"张三"}).explain()
{explainVersion: '1',queryPlanner: {namespace: 'test.user',indexFilterSet: false,parsedQuery: {name: {'$eq': '张三'}},queryHash: 'A2F868FD',planCacheKey: 'A2F868FD',maxIndexedOrSolutionsReached: false,maxIndexedAndSolutionsReached: false,maxScansToExplodeReached: false,winningPlan: {stage: 'COLLSCAN',filter: {name: {'$eq': '张三'}},direction: 'forward'},rejectedPlans: []},command: {find: 'user',filter: {name: '张三'},'$db': 'test'},serverInfo: {host: 'ADMIN',port: 27017,version: '7.0.6',gitVersion: '66cdc1f28172cb33ff68263050d73d4ade73b9a4'},serverParameters: {internalQueryFacetBufferSizeBytes: 104857600,internalQueryFacetMaxOutputDocSizeBytes: 104857600,internalLookupStageIntermediateDocumentMaxSizeBytes: 104857600,internalDocumentSourceGroupMaxMemoryBytes: 104857600,internalQueryMaxBlockingSortMemoryUsageBytes: 104857600,internalQueryProhibitBlockingMergeOnMongoS: 0,internalQueryMaxAddToSetBytes: 104857600,internalDocumentSourceSetWindowFieldsMaxMemoryBytes: 104857600,internalQueryFrameworkControl: 'trySbeRestricted'},ok: 1
}

关键点看： "stage" : "COLLSCAN", 表示全集合扫描

创建索引后

下面对name建立索引

db.user.createIndex({name:1})

看效果

> db.user.find({"name":"张三"}).explain()
{explainVersion: '1',queryPlanner: {namespace: 'test.user',indexFilterSet: false,parsedQuery: {name: {'$eq': '张三'}},queryHash: 'A2F868FD',planCacheKey: 'A3E454E0',maxIndexedOrSolutionsReached: false,maxIndexedAndSolutionsReached: false,maxScansToExplodeReached: false,winningPlan: {stage: 'FETCH',inputStage: {stage: 'IXSCAN',keyPattern: {name: 1},indexName: 'name_1',isMultiKey: false,multiKeyPaths: {name: []},isUnique: false,isSparse: false,isPartial: false,indexVersion: 2,direction: 'forward',indexBounds: {name: ['["张三", "张三"]']}}},rejectedPlans: []},command: {find: 'user',filter: {name: '张三'},'$db': 'test'},serverInfo: {host: 'ADMIN',port: 27017,version: '7.0.6',gitVersion: '66cdc1f28172cb33ff68263050d73d4ade73b9a4'},serverParameters: {internalQueryFacetBufferSizeBytes: 104857600,internalQueryFacetMaxOutputDocSizeBytes: 104857600,internalLookupStageIntermediateDocumentMaxSizeBytes: 104857600,internalDocumentSourceGroupMaxMemoryBytes: 104857600,internalQueryMaxBlockingSortMemoryUsageBytes: 104857600,internalQueryProhibitBlockingMergeOnMongoS: 0,internalQueryMaxAddToSetBytes: 104857600,internalDocumentSourceSetWindowFieldsMaxMemoryBytes: 104857600,internalQueryFrameworkControl: 'trySbeRestricted'},ok: 1
}