Mongodb的版本：v3.4
db.h.reateIndex({'port':1});
db.h.reateIndex({'geo.city':1});在使用的时候
db.h.find({'port':'80','geo.city':'Taipei'}，{'port':1,'geo.city':1,'geo.country':1})explain('executionStats')
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 280952,
"executionTimeMillis" : 10056,
"totalKeysExamined" : 879232,
"totalDocsExamined" : 879232,
"executionStages" : {
"stage" : "PROJECTION",
"nReturned" : 280952,
"executionTimeMillisEstimate" : 9763,
"works" : 879233,
"advanced" : 280952,
"needTime" : 598280,
"needYield" : 0,
"saveState" : 6915,
"restoreState" : 6915,
"isEOF" : 1,
"invalidates" : 0,
"transformBy" : {
"port" : 1,
"geo.city" : 1,
"geo.country" : 1,
},
"inputStage" : {
"stage" : "FETCH",
"filter" : {
"geo.city" : {
"$eq" : "Taipei"
}
},
"nReturned" : 280952,
"executionTimeMillisEstimate" : 9246,
"works" : 879233,
"advanced" : 280952,
"needTime" : 598280,
"needYield" : 0,
"saveState" : 6915,
"restoreState" : 6915,
"isEOF" : 1,
"invalidates" : 0,
"docsExamined" : 879232,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 879232,
"executionTimeMillisEstimate" : 466,
"works" : 879233,
"advanced" : 879232,
"needTime" : 0,
"needYield" : 0,
"saveState" : 6915,
"restoreState" : 6915,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"port" : 1
},
"indexName" : "port_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"port" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"port" : [
"[\"80\", \"80\"]"
]
},
"keysExamined" : 879232,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
}
像上面的例子，除了端口使用了索引吗？还是两个都使用了，如果两个都使用了，那还要建立复合索引吗？
谢谢
自己回答一下，上面有用到索引，但是只有一部分。
如果建立复合索引，将会更快的搜索到。
所以，组合搜索还是得用复合索引。