MongoDB版本v3.2.1
引擎：wiredTiger
例如，这是典型的快速查找查询：
{
"op" : "query",
"ns" : "partkom.cross",
"query" : {
"find" : "cross",
"filter" : {
"part_id1" : NumberInt(2148967),
"maker_id1" : NumberInt(833)
},
"shardVersion" : [
Timestamp(60, 0),
ObjectId("56f50db2ebc50fdfa98e50df")
]
},
"keysExamined" : NumberInt(20),
"docsExamined" : NumberInt(20),
"cursorExhausted" : true,
"keyUpdates" : NumberInt(0),
"writeConflicts" : NumberInt(0),
"numYield" : NumberInt(0),
"locks" : {
"Global" : {
"acquireCount" : {
"r" : NumberLong(2)
}
},
"Database" : {
"acquireCount" : {
"r" : NumberLong(1)
}
},
"Collection" : {
"acquireCount" : {
"r" : NumberLong(1)
}
}
},
"nreturned" : NumberInt(20),
"responseLength" : NumberInt(1666),
"protocol" : "op_command",
"millis" : NumberInt(1),
"execStats" : {
"stage" : "FETCH",
"nReturned" : NumberInt(20),
"executionTimeMillisEstimate" : NumberInt(0),
"works" : NumberInt(21),
"advanced" : NumberInt(20),
"needTime" : NumberInt(0),
"needYield" : NumberInt(0),
"saveState" : NumberInt(0),
"restoreState" : NumberInt(0),
"isEOF" : NumberInt(1),
"invalidates" : NumberInt(0),
"docsExamined" : NumberInt(20),
"alreadyHasObj" : NumberInt(0),
"inputStage" : {
"stage" : "SHARDING_FILTER",
"nReturned" : NumberInt(20),
"executionTimeMillisEstimate" : NumberInt(0),
"works" : NumberInt(21),
"advanced" : NumberInt(20),
"needTime" : NumberInt(0),
"needYield" : NumberInt(0),
"saveState" : NumberInt(0),
"restoreState" : NumberInt(0),
"isEOF" : NumberInt(1),
"invalidates" : NumberInt(0),
"chunkSkips" : NumberInt(0),
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : NumberInt(20),
"executionTimeMillisEstimate" : NumberInt(0),
"works" : NumberInt(21),
"advanced" : NumberInt(20),
"needTime" : NumberInt(0),
"needYield" : NumberInt(0),
"saveState" : NumberInt(0),
"restoreState" : NumberInt(0),
"isEOF" : NumberInt(1),
"invalidates" : NumberInt(0),
"keyPattern" : {
"maker_id1" : NumberInt(1),
"part_id1" : NumberInt(1)
},
"indexName" : "maker_id1_1_part_id1_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : NumberInt(1),
"direction" : "forward",
"indexBounds" : {
"maker_id1" : [
"[833, 833]"
],
"part_id1" : [
"[2148967, 2148967]"
]
},
"keysExamined" : NumberInt(20),
"dupsTested" : NumberInt(0),
"dupsDropped" : NumberInt(0),
"seenInvalidated" : NumberInt(0)
}
}
},
"ts" : ISODate("2016-04-06T07:41:56.586+0000"),
"client" : "172.16.10.217",
"allUsers" : [
],
"user" : ""
}
但有时这个查询需要比平常更长的时间（超过100毫秒）。对我来说很长一段时间！
{
"op" : "query",
"ns" : "partkom.cross",
"query" : {
"find" : "cross",
"filter" : {
"part_id1" : NumberInt(214251369),
"maker_id1" : NumberInt(839)
},
"shardVersion" : [
Timestamp(60, 0),
ObjectId("56f50db2ebc50fdfa98e50df")
]
},
"keysExamined" : NumberInt(15),
"docsExamined" : NumberInt(15),
"cursorExhausted" : true,
"keyUpdates" : NumberInt(0),
"writeConflicts" : NumberInt(0),
"numYield" : NumberInt(3),
"locks" : {
"Global" : {
"acquireCount" : {
"r" : NumberLong(8)
}
},
"Database" : {
"acquireCount" : {
"r" : NumberLong(4)
}
},
"Collection" : {
"acquireCount" : {
"r" : NumberLong(4)
}
}
},
"nreturned" : NumberInt(15),
"responseLength" : NumberInt(1286),
"protocol" : "op_command",
"millis" : NumberInt(145),
"execStats" : {
"stage" : "FETCH",
"nReturned" : NumberInt(15),
"executionTimeMillisEstimate" : NumberInt(140),
"works" : NumberInt(16),
"advanced" : NumberInt(15),
"needTime" : NumberInt(0),
"needYield" : NumberInt(0),
"saveState" : NumberInt(3),
"restoreState" : NumberInt(3),
"isEOF" : NumberInt(1),
"invalidates" : NumberInt(0),
"docsExamined" : NumberInt(15),
"alreadyHasObj" : NumberInt(0),
"inputStage" : {
"stage" : "SHARDING_FILTER",
"nReturned" : NumberInt(15),
"executionTimeMillisEstimate" : NumberInt(0),
"works" : NumberInt(16),
"advanced" : NumberInt(15),
"needTime" : NumberInt(0),
"needYield" : NumberInt(0),
"saveState" : NumberInt(3),
"restoreState" : NumberInt(3),
"isEOF" : NumberInt(1),
"invalidates" : NumberInt(0),
"chunkSkips" : NumberInt(0),
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : NumberInt(15),
"executionTimeMillisEstimate" : NumberInt(0),
"works" : NumberInt(16),
"advanced" : NumberInt(15),
"needTime" : NumberInt(0),
"needYield" : NumberInt(0),
"saveState" : NumberInt(3),
"restoreState" : NumberInt(3),
"isEOF" : NumberInt(1),
"invalidates" : NumberInt(0),
"keyPattern" : {
"maker_id1" : NumberInt(1),
"part_id1" : NumberInt(1)
},
"indexName" : "maker_id1_1_part_id1_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : NumberInt(1),
"direction" : "forward",
"indexBounds" : {
"maker_id1" : [
"[839, 839]"
],
"part_id1" : [
"[214251369, 214251369]"
]
},
"keysExamined" : NumberInt(15),
"dupsTested" : NumberInt(0),
"dupsDropped" : NumberInt(0),
"seenInvalidated" : NumberInt(0)
}
}
},
"ts" : ISODate("2016-04-06T07:27:20.514+0000"),
"client" : "172.16.10.217",
"allUsers" : [
],
"user" : ""
}
为什么在最后一个例子中估计太长？ "executionTimeMillisEstimate" : NumberInt(140)？
如何理解为什么它工作145ms？ （"millis" : NumberInt(145)）
内存中的所有索引。