MongoDb 4.2：在分片集合上进行索引扫描查询非常慢
针对分片集合（MongoDb 4.2.1）运行以下查询时，我遇到非常慢的性能：
db.dc.find({
'hierarchy.company': 'PICCOLO_SRL',
"hierarchy.brand": 'PICCOLO_PICCOLO',
'dcheader.doc_date': {
$gte: 1569016800,
$lte: 1571695140
},
'dcheader.cardnr': '0461000402452'})
查询使用以下索引，而不是分片索引：
"key" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
}
该集合包含450万个文档，其大小为20.2GB。碎片索引是哈希类型，碎片是平衡的。
查询执行计划如下：
{
"queryPlanner" : {
"mongosPlannerVersion" : 1,
"winningPlan" : {
"stage" : "SHARD_MERGE",
"shards" : [
{
"shardName" : "rsshard1",
"connectionString" : "rsshard1/kcc1prod.sipos.it:27020,kcc2prod.sipos.it:27020,kcc3prod.sipos.it:27020",
"serverInfo" : {
"host" : "kcc2prod.sipos.it",
"port" : 27020,
"version" : "4.2.1",
"gitVersion" : "edf6d45851c0b9ee15548f0f847df141764a317e"
},
"plannerVersion" : 1,
"namespace" : "kaneda.dc",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"dcheader.cardnr" : {
"$eq" : "0461000402452"
}
},
{
"hierarchy.brand" : {
"$eq" : "PICCOLO_PICCOLO"
}
},
{
"hierarchy.company" : {
"$eq" : "PICCOLO_SRL"
}
},
{
"dcheader.doc_date" : {
"$lte" : 1571695140
}
},
{
"dcheader.doc_date" : {
"$gte" : 1569016800
}
}
]
},
"winningPlan" : {
"stage" : "SHARDING_FILTER",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
},
"indexName" : "IndexCardnrDocDate",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.doc_date" : [ ],
"dcheader.cardnr" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"dcheader.doc_date" : [
"[1569016800.0, 1571695140.0]"
],
"dcheader.cardnr" : [
"[\"0461000402452\", \"0461000402452\"]"
]
}
}
}
},
"rejectedPlans" : [
{
"stage" : "SHARDING_FILTER",
"inputStage" : {
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"dcheader.cardnr" : {
"$eq" : "0461000402452"
}
},
{
"dcheader.doc_date" : {
"$lte" : 1571695140
}
},
{
"dcheader.doc_date" : {
"$gte" : 1569016800
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"hierarchy.zone" : 1,
"hierarchy.pdv" : 1,
"dcheader.idscontrino" : 1
},
"indexName" : "IndexIdScontrino",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"hierarchy.zone" : [ ],
"hierarchy.pdv" : [ ],
"dcheader.idscontrino" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"hierarchy.zone" : [
"[MinKey, MaxKey]"
],
"hierarchy.pdv" : [
"[MinKey, MaxKey]"
],
"dcheader.idscontrino" : [
"[MinKey, MaxKey]"
]
}
}
}
},
{
"stage" : "SHARDING_FILTER",
"inputStage" : {
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"dcheader.cardnr" : {
"$eq" : "0461000402452"
}
},
{
"dcheader.doc_date" : {
"$lte" : 1571695140
}
},
{
"dcheader.doc_date" : {
"$gte" : 1569016800
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.deptnr" : 1,
"dcheader.tillid" : 1,
"dcheader.numdocumentogestionale" : 1,
"dcheader.fiscalprinternr" : 1
},
"indexName" : "IndexDcDocGestionale",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.deptnr" : [ ],
"dcheader.tillid" : [ ],
"dcheader.numdocumentogestionale" : [ ],
"dcheader.fiscalprinternr" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"dcheader.deptnr" : [
"[MinKey, MaxKey]"
],
"dcheader.tillid" : [
"[MinKey, MaxKey]"
],
"dcheader.numdocumentogestionale" : [
"[MinKey, MaxKey]"
],
"dcheader.fiscalprinternr" : [
"[MinKey, MaxKey]"
]
}
}
}
}
]
},
{
"shardName" : "rsshard2",
"connectionString" : "rsshard2/kcc1prod.sipos.it:27021,kcc2prod.sipos.it:27021,kcc3prod.sipos.it:27021",
"serverInfo" : {
"host" : "kcc3prod.sipos.it",
"port" : 27021,
"version" : "4.2.1",
"gitVersion" : "edf6d45851c0b9ee15548f0f847df141764a317e"
},
"plannerVersion" : 1,
"namespace" : "kaneda.dc",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"dcheader.cardnr" : {
"$eq" : "0461000402452"
}
},
{
"hierarchy.brand" : {
"$eq" : "PICCOLO_PICCOLO"
}
},
{
"hierarchy.company" : {
"$eq" : "PICCOLO_SRL"
}
},
{
"dcheader.doc_date" : {
"$lte" : 1571695140
}
},
{
"dcheader.doc_date" : {
"$gte" : 1569016800
}
}
]
},
"winningPlan" : {
"stage" : "SHARDING_FILTER",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
},
"indexName" : "IndexCardnrDocDate",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.doc_date" : [ ],
"dcheader.cardnr" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"dcheader.doc_date" : [
"[1569016800.0, 1571695140.0]"
],
"dcheader.cardnr" : [
"[\"0461000402452\", \"0461000402452\"]"
]
}
}
}
},
"rejectedPlans" : [
{
"stage" : "SHARDING_FILTER",
"inputStage" : {
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"dcheader.cardnr" : {
"$eq" : "0461000402452"
}
},
{
"dcheader.doc_date" : {
"$lte" : 1571695140
}
},
{
"dcheader.doc_date" : {
"$gte" : 1569016800
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"hierarchy.zone" : 1,
"hierarchy.pdv" : 1,
"dcheader.idscontrino" : 1
},
"indexName" : "IndexIdScontrino",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"hierarchy.zone" : [ ],
"hierarchy.pdv" : [ ],
"dcheader.idscontrino" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"hierarchy.zone" : [
"[MinKey, MaxKey]"
],
"hierarchy.pdv" : [
"[MinKey, MaxKey]"
],
"dcheader.idscontrino" : [
"[MinKey, MaxKey]"
]
}
}
}
},
{
"stage" : "SHARDING_FILTER",
"inputStage" : {
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"dcheader.cardnr" : {
"$eq" : "0461000402452"
}
},
{
"dcheader.doc_date" : {
"$lte" : 1571695140
}
},
{
"dcheader.doc_date" : {
"$gte" : 1569016800
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.deptnr" : 1,
"dcheader.tillid" : 1,
"dcheader.numdocumentogestionale" : 1,
"dcheader.fiscalprinternr" : 1
},
"indexName" : "IndexDcDocGestionale",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.deptnr" : [ ],
"dcheader.tillid" : [ ],
"dcheader.numdocumentogestionale" : [ ],
"dcheader.fiscalprinternr" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"dcheader.deptnr" : [
"[MinKey, MaxKey]"
],
"dcheader.tillid" : [
"[MinKey, MaxKey]"
],
"dcheader.numdocumentogestionale" : [
"[MinKey, MaxKey]"
],
"dcheader.fiscalprinternr" : [
"[MinKey, MaxKey]"
]
}
}
}
}
]
}
]
}
},
"executionStats" : {
"nReturned" : 0,
"executionTimeMillis" : 170263,
"totalKeysExamined" : 555702,
"totalDocsExamined" : 0,
"executionStages" : {
"stage" : "SHARD_MERGE",
"nReturned" : 0,
"executionTimeMillis" : 170263,
"totalKeysExamined" : 555702,
"totalDocsExamined" : 0,
"totalChildMillis" : 255673,
"shards" : [
{
"shardName" : "rsshard1",
"executionSuccess" : true,
"executionStages" : {
"stage" : "SHARDING_FILTER",
"nReturned" : 0,
"executionTimeMillisEstimate" : 1447,
"works" : 202303,
"advanced" : 0,
"needTime" : 202301,
"needYield" : 0,
"saveState" : 6882,
"restoreState" : 6882,
"isEOF" : 1,
"chunkSkips" : 0,
"inputStage" : {
"stage" : "FETCH",
"nReturned" : 0,
"executionTimeMillisEstimate" : 1428,
"works" : 202302,
"advanced" : 0,
"needTime" : 202301,
"needYield" : 0,
"saveState" : 6882,
"restoreState" : 6882,
"isEOF" : 1,
"docsExamined" : 0,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 0,
"executionTimeMillisEstimate" : 1428,
"works" : 202302,
"advanced" : 0,
"needTime" : 202301,
"needYield" : 0,
"saveState" : 6882,
"restoreState" : 6882,
"isEOF" : 1,
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
},
"indexName" : "IndexCardnrDocDate",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.doc_date" : [ ],
"dcheader.cardnr" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"dcheader.doc_date" : [
"[1569016800.0, 1571695140.0]"
],
"dcheader.cardnr" : [
"[\"0461000402452\", \"0461000402452\"]"
]
},
"keysExamined" : 202302,
"seeks" : 202302,
"dupsTested" : 0,
"dupsDropped" : 0,
"indexDef" : {
"indexName" : "IndexCardnrDocDate",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.doc_date" : [ ],
"dcheader.cardnr" : [ ]
},
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"direction" : "forward"
}
}
}
}
},
{
"shardName" : "rsshard2",
"executionSuccess" : true,
"executionStages" : {
"stage" : "SHARDING_FILTER",
"nReturned" : 0,
"executionTimeMillisEstimate" : 1677,
"works" : 353401,
"advanced" : 0,
"needTime" : 353399,
"needYield" : 0,
"saveState" : 12612,
"restoreState" : 12612,
"isEOF" : 1,
"chunkSkips" : 0,
"inputStage" : {
"stage" : "FETCH",
"nReturned" : 0,
"executionTimeMillisEstimate" : 1660,
"works" : 353400,
"advanced" : 0,
"needTime" : 353399,
"needYield" : 0,
"saveState" : 12612,
"restoreState" : 12612,
"isEOF" : 1,
"docsExamined" : 0,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 0,
"executionTimeMillisEstimate" : 1656,
"works" : 353400,
"advanced" : 0,
"needTime" : 353399,
"needYield" : 0,
"saveState" : 12612,
"restoreState" : 12612,
"isEOF" : 1,
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
},
"indexName" : "IndexCardnrDocDate",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.doc_date" : [ ],
"dcheader.cardnr" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"hierarchy.company" : [
"[\"PICCOLO_SRL\", \"PICCOLO_SRL\"]"
],
"hierarchy.brand" : [
"[\"PICCOLO_PICCOLO\", \"PICCOLO_PICCOLO\"]"
],
"dcheader.doc_date" : [
"[1569016800.0, 1571695140.0]"
],
"dcheader.cardnr" : [
"[\"0461000402452\", \"0461000402452\"]"
]
},
"keysExamined" : 353400,
"seeks" : 353400,
"dupsTested" : 0,
"dupsDropped" : 0,
"indexDef" : {
"indexName" : "IndexCardnrDocDate",
"isMultiKey" : false,
"multiKeyPaths" : {
"hierarchy.company" : [ ],
"hierarchy.brand" : [ ],
"dcheader.doc_date" : [ ],
"dcheader.cardnr" : [ ]
},
"keyPattern" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.doc_date" : 1,
"dcheader.cardnr" : 1
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"direction" : "forward"
}
}
}
}
}
]
}
},
"ok" : 1,
"operationTime" : Timestamp(1571924213, 6),
"$clusterTime" : {
"clusterTime" : Timestamp(1571924213, 6),
"signature" : {
"hash" : BinData(0,"YOMe4acOH+iIfoHlsq/dCErNiZc="),
"keyId" : 6708447541475672066
}
}
}
正如您所看到的，似乎SHARD_MERGE阶段大约需要168000毫秒：有人可以解释为什么吗？
请注意，使用以前的MongoDb版本（3.6），我从未有过如此糟糕的表现。
我还没有找到有关SHARD_MERGE阶段的详细信息：哪个进程执行此任务（mongod或mongos）？在此阶段会发生什么？
我的体系结构由三台Centos 7机器组成，每台机器托管三个mongod进程（shard1副本集，shard2副本集和配置副本集）和一个mongos进程。
2 个答案:
答案 0 :(得分：0)
该解释计划中显示的阶段按执行顺序为：
在mongod碎片上：
IXSCAN-将查询与索引值进行比较
FETCH-检索完整文档
SHARDING_FILTER-删除所有不是分片所有的文档（即孤儿）
在mongos：
SHARD_MERGE-等待，然后合并分片中的结果集
每个分片的执行时间与SHARD_MERGE阶段之间的巨大差异表明，一个分片的启动时间比另一个分片要晚得多，这延迟了响应，或者此处可能存在时钟偏斜。
答案 1 :(得分：0)
您可以尝试将索引顺序更改为此。
"key" : {
"hierarchy.company" : 1,
"hierarchy.brand" : 1,
"dcheader.cardnr" : 1
"dcheader.doc_date" : 1,
}
通常的经验法则是索引字段的顺序应为以下顺序。
- 范围字段之前的相等字段
- 在范围字段之前对字段进行排序
- 排序字段之前的相等字段
在您的情况下，“范围”字段（doc_date）在“平等”字段（cardnr）之前。
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