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Type:
Bug
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Resolution: Won't Fix
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Priority:
Major - P3
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None
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Affects Version/s: 2.2.4, 2.4.1
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Component/s: Diagnostics, Index Maintenance
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None
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Fully Compatible
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ALL
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None
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3
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None
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None
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None
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None
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None
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None
Some index accesses update the global index counters; some don't.
MongoDB shell version: 2.2.4
connecting to: test
> db.version()
2.2.4
> db.hostInfo().os
{ "type" : "Linux", "name" : "Ubuntu", "version" : "12.04" }
> show dbs
local (empty)
> db.test.insert({a:1})
> db.test.ensureIndex({a:1})
> db.serverStatus().indexCounters.btree
{
"accesses" : 1,
"hits" : 1,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
> db.test.find()
{ "_id" : ObjectId("51632bd680036fc7eb0cbdea"), "a" : 1 }
> db.test.find({_id: ObjectId("51632bd680036fc7eb0cbdea")})
{ "_id" : ObjectId("51632bd680036fc7eb0cbdea"), "a" : 1 }
> db.serverStatus().indexCounters.btree
{
"accesses" : 2,
"hits" : 2,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
> db.test.find({a:1})
{ "_id" : ObjectId("51632bd680036fc7eb0cbdea"), "a" : 1 }
> db.test.find({a:1}).explain()
{
"cursor" : "BtreeCursor a_1",
"isMultiKey" : false,
"n" : 1,
"nscannedObjects" : 1,
"nscanned" : 1,
"nscannedObjectsAllPlans" : 1,
"nscannedAllPlans" : 1,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
"a" : [
[
1,
1
]
]
},
"server" : "tad-ubuntu:27017"
}
> db.serverStatus().indexCounters.btree
{
"accesses" : 2,
"hits" : 2,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
MongoDB shell version: 2.4.1
connecting to: test
> db.version()
2.4.1
> db.hostInfo().os
{ "type" : "Linux", "name" : "Ubuntu", "version" : "12.04" }
> show dbs
local 0.078125GB
> db.test.insert({a:1})
> db.test.ensureIndex({a:1})
> db.serverStatus().indexCounters
{
"accesses" : 1,
"hits" : 1,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
> db.test.find()
{ "_id" : ObjectId("51632d682b2597dfbeae7f92"), "a" : 1 }
> db.test.find({_id: ObjectId("51632d682b2597dfbeae7f92")})
{ "_id" : ObjectId("51632d682b2597dfbeae7f92"), "a" : 1 }
> db.serverStatus().indexCounters
{
"accesses" : 2,
"hits" : 2,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
> db.test.find({a:1})
{ "_id" : ObjectId("51632d682b2597dfbeae7f92"), "a" : 1 }
> db.test.find({a:1}).explain()
{
"cursor" : "BtreeCursor a_1",
"isMultiKey" : false,
"n" : 1,
"nscannedObjects" : 1,
"nscanned" : 1,
"nscannedObjectsAllPlans" : 1,
"nscannedAllPlans" : 1,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
"a" : [
[
1,
1
]
]
},
"server" : "tad-ubuntu:27017"
}
> db.serverStatus().indexCounters
{
"accesses" : 2,
"hits" : 2,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
Indexed access using _id adds to the index counters. Indexed access using the "a" key in this example does not add to the index counters.