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Type:
Bug
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Resolution: Done
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Priority:
Major - P3
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Affects Version/s: 2.6.0-rc1
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Component/s: Diagnostics, Querying
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ALL
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Explain for indexed $or queries always incorrectly sets 'nscannedObjects' to zero, even when the query is not covered.
To reproduce:
> db.foo.ensureIndex({a:1})
> db.foo.ensureIndex({b:1})
> for(i=0;i<10;i++){db.foo.insert({a:1,b:1})}
> db.foo.find({$or:[{a:1},{b:1}]}).explain().nscannedObjects
0 // should be 20 (well, arguably should be 10, but at least in 2.4.9 this is 20)
Full explain output:
> db.foo.find({$or:[{a:1},{b:1}]}).explain(true)
{
"clauses" : [
{
"cursor" : "BtreeCursor a_1",
"isMultiKey" : false,
"n" : 10,
"nscannedObjects" : 0,
"nscanned" : 10,
"scanAndOrder" : false,
"indexOnly" : false,
"nChunkSkips" : 0,
"indexBounds" : {
"a" : [
[
1,
1
]
]
}
},
{
"cursor" : "BtreeCursor b_1",
"isMultiKey" : false,
"n" : 10,
"nscannedObjects" : 0,
"nscanned" : 10,
"scanAndOrder" : false,
"indexOnly" : false,
"nChunkSkips" : 0,
"indexBounds" : {
"b" : [
[
1,
1
]
]
}
}
],
"cursor" : "QueryOptimizerCursor",
"n" : 10,
"nscannedObjects" : 0,
"nscanned" : 20,
"nscannedObjectsAllPlans" : 0,
"nscannedAllPlans" : 20,
"scanAndOrder" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 1,
"allPlans" : [
{
"clauses" : [
{
"cursor" : "BtreeCursor a_1",
"isMultiKey" : false,
"n" : 10,
"nscannedObjects" : 0,
"nscanned" : 10,
"scanAndOrder" : false,
"indexOnly" : false,
"nChunkSkips" : 0,
"indexBounds" : {
"a" : [
[
1,
1
]
]
}
},
{
"cursor" : "BtreeCursor b_1",
"isMultiKey" : false,
"n" : 10,
"nscannedObjects" : 0,
"nscanned" : 10,
"scanAndOrder" : false,
"indexOnly" : false,
"nChunkSkips" : 0,
"indexBounds" : {
"b" : [
[
1,
1
]
]
}
}
],
"cursor" : "QueryOptimizerCursor",
"n" : 10,
"nscannedObjects" : 0,
"nscanned" : 20,
"scanAndOrder" : false,
"nChunkSkips" : 0
}
],
"server" : "Rassi-MacBook-Pro.local:27017",
"filterSet" : false,
"stats" : {
"type" : "FETCH",
"works" : 22,
"yields" : 0,
"unyields" : 0,
"invalidates" : 0,
"advanced" : 10,
"needTime" : 11,
"needFetch" : 0,
"isEOF" : 1,
"alreadyHasObj" : 0,
"forcedFetches" : 0,
"matchTested" : 0,
"children" : [
{
"type" : "OR",
"works" : 22,
"yields" : 0,
"unyields" : 0,
"invalidates" : 0,
"advanced" : 10,
"needTime" : 11,
"needFetch" : 0,
"isEOF" : 1,
"dupsTested" : 20,
"dupsDropped" : 10,
"locsForgotten" : 0,
"matchTested_0" : 0,
"matchTested_1" : 0,
"children" : [
{
"type" : "IXSCAN",
"works" : 11,
"yields" : 0,
"unyields" : 0,
"invalidates" : 0,
"advanced" : 10,
"needTime" : 0,
"needFetch" : 0,
"isEOF" : 1,
"keyPattern" : "{ a: 1.0 }",
"boundsVerbose" : "field #0['a']: [1.0, 1.0]",
"isMultiKey" : 0,
"yieldMovedCursor" : 0,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0,
"matchTested" : 0,
"keysExamined" : 10,
"children" : [ ]
},
{
"type" : "IXSCAN",
"works" : 11,
"yields" : 0,
"unyields" : 0,
"invalidates" : 0,
"advanced" : 10,
"needTime" : 0,
"needFetch" : 0,
"isEOF" : 1,
"keyPattern" : "{ b: 1.0 }",
"boundsVerbose" : "field #0['b']: [1.0, 1.0]",
"isMultiKey" : 0,
"yieldMovedCursor" : 0,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0,
"matchTested" : 0,
"keysExamined" : 10,
"children" : [ ]
}
]
}
]
}
}
>
- related to
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- Closed
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