最近遇到的一个MongoDB索引顺序的问题
最近遇到个mongo慢查问题，查询这样子：
db.tb1.find({status:'normal', lastReviewTime:{$gte:1583038740,$lte:1585285140}}).sort({createdTime:-1}).limit(30)执行计划如下：
> db.tb1.find({status:'normal', lastReviewTime:{$gte:1583038740,$lte:1585285140}}).sort({createdTime:-1}).limit(30).explain()
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "db1.tb1",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"status" : {
"$eq" : "normal"
}
},
{
"lastReviewTime" : {
"$lte" : 1585285140
}
},
{
"lastReviewTime" : {
"$gte" : 1583038740
}
}
]
},
"winningPlan" : {
"stage" : "SORT",
"sortPattern" : {
"createdTime" : -1
},
"limitAmount" : 30,
"inputStage" : {
"stage" : "SORT_KEY_GENERATOR",
"inputStage" : {
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"lastReviewTime" : {
"$lte" : 1585285140
}
},
{
"lastReviewTime" : {
"$gte" : 1583038740
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"status" : 1,
"type" : 1,
"executionTime" : 1
},
"indexName" : "idx_stats_typ_execTime", # 走的这个索引
"isMultiKey" : false,
"multiKeyPaths" : {
"status" : [ ],
"type" : [ ],
"executionTime" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"status" : [
"[\"normal\", \"normal\"]"
],
"type" : [
"[MinKey, MaxKey]"
],
"executionTime" : [
"[MinKey, MaxKey]"
]
}
}
}
}
},
"rejectedPlans" : [
{
"stage" : "SORT",
"sortPattern" : {
"createdTime" : -1
},
"limitAmount" : 30,
"inputStage" : {
"stage" : "SORT_KEY_GENERATOR",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"lastReviewTime" : 1,
"status" : 1,
"createdTime" : -1
},
"indexName" : "lastReviewTime_1_status_1_createdTime_-1",
"isMultiKey" : false,
"multiKeyPaths" : {
"lastReviewTime" : [ ],
"status" : [ ],
"createdTime" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"lastReviewTime" : [
"[1583038740.0, 1585285140.0]"
],
"status" : [
"[\"normal\", \"normal\"]"
],
"createdTime" : [
"[MaxKey, MinKey]"
]
}
}
}
}
},
{
"stage" : "SORT",
"sortPattern" : {
"createdTime" : -1
},
"limitAmount" : 30,
"inputStage" : {
"stage" : "SORT_KEY_GENERATOR",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"lastReviewTime" : -1,
"status" : 1
},
"indexName" : "lastReviewTime_-1_status_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"lastReviewTime" : [ ],
"status" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"lastReviewTime" : [
"[1585285140.0, 1583038740.0]"
],
"status" : [
"[\"normal\", \"normal\"]"
]
}
}
}
}
}
]
},
"ok" : 1
}这种情况下，我们的索引顺序需要注意下，这样写：
{精确匹配字段,排序字段,范围查询字段} 这样的索引排序会更为高效
db.tb1.createIndex({status:1,createdTime:-1,lastReviewTime:1},{background:true})加完索引后，可以发现查询速度有质的飞越了。
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原始发表：2020-03-30 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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