mongo索引性能
标签（空格分隔）： mongo
https://www.cnblogs.com/c-abc/p/6023824.html
测试mongo索引性能
有索引，每个值都是唯一值
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 0, ## 总耗时
"totalKeysExamined" : 1, ##
"totalDocsExamined" : 1, ## 检索文档数
"executionStages" : {
"stage" : "FETCH",
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 2,
"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" : {
"attr" : 1
},
"indexName" : "attr",
"isMultiKey" : false,
"multiKeyPaths" : {
"attr" : []
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"attr" : [
"[\"所属国家\", \"所属国家\"]"
]
},
"keysExamined" : 1,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
无索引，每个值都是唯一值
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 6,
"totalKeysExamined" : 0,
"totalDocsExamined" : 4723,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"attr" : {
"$eq" : "所属国家"
}
},
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 4725,
"advanced" : 1,
"needTime" : 4723,
"needYield" : 0,
"saveState" : 36,
"restoreState" : 36,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 4723
}
},可以看出，有索引后只需要检索一个文档，并且时间由原来的6降低到了0
有索引，只有两个值
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 4723,
"executionTimeMillis" : 13, ##
"totalKeysExamined" : 4723, ## 这里有查找索引需要的时间
"totalDocsExamined" : 4723, ##
"executionStages" : {
"stage" : "FETCH",
"nReturned" : 4723,
"executionTimeMillisEstimate" : 20,
"works" : 4724,
"advanced" : 4723,
"needTime" : 0,
"needYield" : 0,
"saveState" : 36,
"restoreState" : 36,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 4723,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 4723,
"executionTimeMillisEstimate" : 20,
"works" : 4724,
"advanced" : 4723,
"needTime" : 0,
"needYield" : 0,
"saveState" : 36,
"restoreState" : 36,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"domain_has_entity" : 1
},
"indexName" : "ha",
"isMultiKey" : false,
"multiKeyPaths" : {
"domain_has_entity" : []
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"domain_has_entity" : [
"[\"False\", \"False\"]"
]
},
"keysExamined" : 4723,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},you无索引，只有两个值
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 4723,
"executionTimeMillis" : 6,
"totalKeysExamined" : 0, ## 可以看出不需要检索key值，所以没有索引反而省时间了
"totalDocsExamined" : 4723,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"domain_has_entity" : {
"$eq" : "False"
}
},
"nReturned" : 4723,
"executionTimeMillisEstimate" : 0,
"works" : 4725,
"advanced" : 4723,
"needTime" : 1,
"needYield" : 0,
"saveState" : 36,
"restoreState" : 36,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 4723
}
},对于个数较少的字段，就不要建索引了，省得他还有查索引的时间
无索引，联合查询
db.getCollection(‘rdf_useful’).find({“entity” : “蒋官屯街道”,”attr” : “辖社区数”}).explain(“executionStats”)
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 974,
"totalKeysExamined" : 0,
"totalDocsExamined" : 1805242,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"$and" : [
{
"attr" : {
"$eq" : "辖社区数" }
},
{
"entity" : {
"$eq" : "蒋官屯街道" }
}
]
},
"nReturned" : 1,
"executionTimeMillisEstimate" : 880,
"works" : 1805244,
"advanced" : 1,
"needTime" : 1805242,
"needYield" : 0,
"saveState" : 14103,
"restoreState" : 14103,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 1805242
}
},只对一个字段建索引，但联合查询
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 0
"totalKeysExamined" : 16,
"totalDocsExamined" : 16,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"attr" : {
"$eq" : "辖社区数"
}
},
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 17,
"advanced" : 1,
"needTime" : 15,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 16,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 16,
"executionTimeMillisEstimate" : 0,
"works" : 17,
"advanced" : 16,
"needTime" : 0,
"needYield" : 0,
"saveState" : 0,
"restoreState" : 0,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"entity" : 1
},
"indexName" : "wn",
"isMultiKey" : false,
"multiKeyPaths" : {
"entity" : []
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"entity" : [
"[\"蒋官屯街道\", \"蒋官屯街道\"]"
]
},
"keysExamined" : 16,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
```建立联合索引，联合查询
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1,
"executionTimeMillis" : 0,
"totalKeysExamined" : 1,
"totalDocsExamined" : 1,
"executionStages" : {
"stage" : "FETCH",
"nReturned" : 1,
"executionTimeMillisEstimate" : 0,
"works" : 2,
"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" : {
"entity" : 1,
"attr" : 1
},
"indexName" : "wn",
"isMultiKey" : false,
"multiKeyPaths" : {
"entity" : [],
"attr" : []
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"entity" : [
"[\"蒋官屯街道\", \"蒋官屯街道\"]"
],
"attr" : [
"[\"辖社区数\", \"辖社区数\"]"
]
},
"keysExamined" : 1,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},