我是MongoDB的新手，尝试使用相当大的数据库设置1个节点。 10亿行，140GB，10个字段。除了one之外的所有字段都有单独的索引，因为我们计划了许多不同的查询，这些查询将组合2或3个字段。
我的问题是MongoDB似乎没有在组合搜索上使用单独的索引。
db.alldata.find({ p: "степанович" })
此搜索的答案不到1秒。
db.alldata.find({ n: "иван" })
这个也是。
但是db.alldata.find（{n：“иван”，p：“степанович”}）
需要永远完成。难道我做错了什么？ 我不想使用组合索引，因为我们有太多不同的查询，甚至单独的索引几乎占用所有RAM（50GB）
已创建索引 。还有 足够的RAM来适应它们。 操作系统是CentOS7，FS是xfs（如果重要的话）。
更新：
db.alldata.find({ n: "иван", p: "степанович"}).explain("allPlansExecution")
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "myDb.alldata",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"n" : {
"$eq" : "иван"
}
},
{
"p" : {
"$eq" : "степанович"
}
}
]
},
"winningPlan" : {
"stage" : "FETCH",
"filter" : {
"n" : {
"$eq" : "иван"
}
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"p" : 1
},
"indexName" : "parentalName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"p" : [
"[\"степанович\", \"степанович\"]"
]
}
}
},
"rejectedPlans" : [
{
"stage" : "FETCH",
"filter" : {
"p" : {
"$eq" : "степанович"
}
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"n" : 1
},
"indexName" : "firstName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"n" : [
"[\"иван\", \"иван\"]"
]
}
}
},
{
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"n" : {
"$eq" : "иван"
}
},
{
"p" : {
"$eq" : "степанович"
}
}
]
},
"inputStage" : {
"stage" : "AND_SORTED",
"inputStages" : [
{
"stage" : "IXSCAN",
"keyPattern" : {
"n" : 1
},
"indexName" : "firstName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"n" : [
"[\"иван\", \"иван\"]"
]
}
},
{
"stage" : "IXSCAN",
"keyPattern" : {
"p" : 1
},
"indexName" : "parentalName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"p" : [
"[\"степанович\", \"степанович\"]"
]
}
}
]
}
}
]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 31,
"executionTimeMillis" : 213504,
"totalKeysExamined" : 124244,
"totalDocsExamined" : 124244,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"n" : {
"$eq" : "иван"
}
},
"nReturned" : 31,
"executionTimeMillisEstimate" : 13160,
"works" : 124246,
"advanced" : 31,
"needTime" : 124213,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 124244,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 124244,
"executionTimeMillisEstimate" : 240,
"works" : 124245,
"advanced" : 124244,
"needTime" : 0,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"p" : 1
},
"indexName" : "parentalName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"p" : [
"[\"степанович\", \"степанович\"]"
]
},
"keysExamined" : 124244,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
},
"allPlansExecution" : [
{
"nReturned" : 18,
"executionTimeMillisEstimate" : 196410,
"totalKeysExamined" : 124245,
"totalDocsExamined" : 124245,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"p" : {
"$eq" : "степанович"
}
},
"nReturned" : 18,
"executionTimeMillisEstimate" : 196410,
"works" : 124245,
"advanced" : 18,
"needTime" : 124227,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 0,
"invalidates" : 0,
"docsExamined" : 124245,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 124245,
"executionTimeMillisEstimate" : 240,
"works" : 124245,
"advanced" : 124245,
"needTime" : 0,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 0,
"invalidates" : 0,
"keyPattern" : {
"n" : 1
},
"indexName" : "firstName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"n" : [
"[\"иван\", \"иван\"]"
]
},
"keysExamined" : 124245,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
{
"nReturned" : 13,
"executionTimeMillisEstimate" : 540,
"totalKeysExamined" : 124245,
"totalDocsExamined" : 13,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"n" : {
"$eq" : "иван"
}
},
{
"p" : {
"$eq" : "степанович"
}
}
]
},
"nReturned" : 13,
"executionTimeMillisEstimate" : 540,
"works" : 124245,
"advanced" : 13,
"needTime" : 124232,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 0,
"invalidates" : 0,
"docsExamined" : 13,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "AND_SORTED",
"nReturned" : 13,
"executionTimeMillisEstimate" : 490,
"works" : 124245,
"advanced" : 13,
"needTime" : 124232,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 0,
"invalidates" : 0,
"flagged" : 0,
"failedAnd_0" : 29865,
"failedAnd_1" : 29858,
"inputStages" : [
{
"stage" : "IXSCAN",
"nReturned" : 74468,
"executionTimeMillisEstimate" : 250,
"works" : 74468,
"advanced" : 74468,
"needTime" : 0,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 0,
"invalidates" : 0,
"keyPattern" : {
"n" : 1
},
"indexName" : "firstName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"n" : [
"[\"иван\", \"иван\"]"
]
},
"keysExamined" : 74468,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
},
{
"stage" : "IXSCAN",
"nReturned" : 49777,
"executionTimeMillisEstimate" : 150,
"works" : 49777,
"advanced" : 49777,
"needTime" : 0,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 0,
"invalidates" : 0,
"keyPattern" : {
"p" : 1
},
"indexName" : "parentalName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"p" : [
"[\"степанович\", \"степанович\"]"
]
},
"keysExamined" : 49777,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
]
}
}
},
{
"nReturned" : 31,
"executionTimeMillisEstimate" : 13160,
"totalKeysExamined" : 124244,
"totalDocsExamined" : 124244,
"executionStages" : {
"stage" : "FETCH",
"filter" : {
"n" : {
"$eq" : "иван"
}
},
"nReturned" : 31,
"executionTimeMillisEstimate" : 13160,
"works" : 124245,
"advanced" : 31,
"needTime" : 124213,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 124244,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 124244,
"executionTimeMillisEstimate" : 240,
"works" : 124245,
"advanced" : 124244,
"needTime" : 0,
"needYield" : 0,
"saveState" : 11965,
"restoreState" : 11965,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"p" : 1
},
"indexName" : "parentalName",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"p" : [
"[\"степанович\", \"степанович\"]"
]
},
"keysExamined" : 124244,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
}
]
},
"serverInfo" : {
"host" : "cass",
"port" : 27017,
"version" : "3.2.4",
"gitVersion" : "e2ee9ffcf9f5a94fad76802e28cc978718bb7a30"
},
"ok" : 1
}
答案 0 :(得分：0)
我的问题是MongoDB似乎没有使用单独的索引 联合搜索。
在MongoDb 2.6之后，MongoDb支持Index Intersection
但是如果需要，你应该使用组合索引。因为prefixes可以处理得很好。
即使使用索引，查询也非常重要。因此，您应该使用基于Create Queries that Ensure Selectivity的查询。因此，您应该选择使用哪个索引，或者使用hint()查询不会使用索引。
在您理解了这些概念之后，您可以measure your indexes并最好地满足您的期望。