【发布时间】：2016-07-13 12:23:52
【问题描述】：
我是 MongoDB 的新手，正在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。除了一个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，它们将组合 2 或 3 个字段。
我的问题是 MongoDB 似乎没有在组合搜索中使用单独的索引。
db.alldata.find({ p: "степанович" })
此搜索不到 1 秒即可回答。
db.alldata.find({ n: "иван" })
这个也是。
但是 db.alldata.find({ n: "иван", p: "степанович" })
需要很长时间才能完成。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，甚至单独的索引也会占用几乎所有 RAM (50GB)
索引被创建。 有足够的 RAM 来容纳它们。 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
}
【问题讨论】：
-
请用解释结果更新您的帖子。
db.alldata.find({ n: "иван", p: "степанович" }).explain("allPlansExecution ")。另外请提及您的 MongoDB 版本，以及您是否使用 mmap 或 Wiredtiger 引擎。 -
"3.2.4" 来自官方 repo 和wiredTiger。添加了 allPlansExecution。
-
谢谢。请也将
collection.getIndexes()的输出发送给我。 -
制作复合索引是浪费时间。没有任何变化，3 个字段的复合索引为 32GB，而 3 个单独的索引只用了 17 个。现在重建单独的索引（这在前台大约需要 10 小时）并将尝试提示。
-
DB 在问题中有所描述。 10 个字段，每个占用 7-10GB，所以我买不起复合索引。它们不适合 RAM。
标签： mongodb performance indexing