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Type:
Bug
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Resolution: Duplicate
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Priority:
Major - P3
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None
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Affects Version/s: 2.6.0-rc0
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Component/s: Querying
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ALL
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None
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The following query takes ~70us in v2.4.9, and ~722us in v2.6.0rc0:
db.regressions.find({$query:{_id: {$exists: false }}, $orderby:{_id:1}});
v2.4.9 explain output:
> db.regressions.find({$query:{_id: {$exists: false }}, $orderby:{_id:1}, $explain:1}).pretty();
{
"cursor" : "BtreeCursor _id_",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 0,
"nscanned" : 0,
"nscannedObjectsAllPlans" : 0,
"nscannedAllPlans" : 0,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
"_id" : [
[
null,
null
]
]
},
"allPlans" : [
{
"cursor" : "BtreeCursor _id_",
"n" : 0,
"nscannedObjects" : 0,
"nscanned" : 0,
"indexBounds" : {
"_id" : [
[
null,
null
]
]
}
}
],
"oldPlan" : {
"cursor" : "BtreeCursor _id_",
"indexBounds" : {
"_id" : [
[
null,
null
]
]
}
},
"server" : "zzyzx:27017"
}
v2.6.0rc0 explain output:
> db.regressions.find({$query:{_id: {$exists: false }}, $orderby:{_id:1}, $explain:1}).pretty();
{
"cursor" : "BtreeCursor _id_",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 1442,
"nscanned" : 1442,
"nscannedObjectsAllPlans" : 1540,
"nscannedAllPlans" : 1540,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 11,
"nChunkSkips" : 0,
"millis" : 4,
"indexBounds" : {
"_id" : [
[
{
"$minElement" : 1
},
{
"$maxElement" : 1
}
]
]
},
"allPlans" : [
{
"cursor" : "BtreeCursor _id_",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 1442,
"nscanned" : 1442,
"scanAndOrder" : false,
"indexOnly" : false,
"nChunkSkips" : 0,
"indexBounds" : {
"_id" : [
[
{
"$minElement" : 1
},
{
"$maxElement" : 1
}
]
]
}
},
{
"cursor" : "BasicCursor",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 98,
"nscanned" : 98,
"scanAndOrder" : true,
"indexOnly" : false,
"nChunkSkips" : 0
}
],
"server" : "zzyzx:27017",
"filterSet" : false,
"stats" : {
"type" : "FETCH",
"works" : 1443,
"yields" : 11,
"unyields" : 11,
"invalidates" : 0,
"advanced" : 0,
"needTime" : 1442,
"needFetch" : 0,
"isEOF" : 1,
"alreadyHasObj" : 0,
"forcedFetches" : 0,
"matchTested" : 0,
"children" : [
{
"type" : "IXSCAN",
"works" : 1442,
"yields" : 11,
"unyields" : 11,
"invalidates" : 0,
"advanced" : 1442,
"needTime" : 0,
"needFetch" : 0,
"isEOF" : 1,
"keyPattern" : "{ _id: 1 }",
"boundsVerbose" : "field #0['_id']: [MinKey, MaxKey]",
"isMultiKey" : 0,
"yieldMovedCursor" : 0,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0,
"matchTested" : 0,
"keysExamined" : 1442,
"children" : [ ]
}
]
}
}
QA-401 results:
> db.regressions.find({$query:{"query":{$not:/where/}}, $orderby:{deltaRatio:-1}}).limit(1).pretty();
{
"_id" : ObjectId("530d751fd8ed4fb55a7bda24"),
"deltaRatio" : "9.99",
"deltaUs" : 650.17,
"v249Avg" : "72.33",
"v249Results" : [
72,
73,
74,
71,
72,
72
],
"rc0Avg" : "722.50",
"rc0Results" : [
715,
767,
704,
709,
708,
732
],
"testId" : "GeneratedTests::GeneratedQuery659[Compound2]",
"query" : "{ query: { _id: { $exists: false } }, orderby: { _id: 1 } }",
"proj" : "{ NONE: 1 }",
"index" : "Compound2",
"rc0Count" : 0,
"v249Count" : 0,
"countsMatch" : true
}
Of course, it's worth noting that this specific query is unlikely to ever be used, given that it sorts by a field which does not exist.
- duplicates
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- Closed
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