-
Type:
Bug
-
Resolution: Gone away
-
Priority:
Major - P3
-
Affects Version/s: 3.6.4
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Labels:None
In the following section: https://docs.mongodb.com/manual/reference/method/db.collection.count/#db.collection.count
we state:
If, however, the query can use an index but the query predicates do not access a single contiguous range of index keys or the query also contains conditions on fields outside the index, then in addition to using the index, MongoDB must also read the documents to return the count.
...
db.collection.find( { a: { $gt: 5 }, b: 5 } ).count()
However, the following ``count()`` does not fetch any document:
replset:PRIMARY> db.movies.explain("executionStats").count({"imdb.rating":{$gt:5}, countries: "USA" })
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "mflix.movies",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"countries" : {
"$eq" : "USA"
}
},
{
"imdb.rating" : {
"$gt" : 5
}
}
]
},
"winningPlan" : {
"stage" : "COUNT",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"imdb.rating" : 1,
"countries" : 1
},
"indexName" : "imdb.rating_1_countries_1",
"isMultiKey" : true,
"multiKeyPaths" : {
"imdb.rating" : [ ],
"countries" : [
"countries"
]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"imdb.rating" : [
"(5.0, inf.0]"
],
"countries" : [
"[\"USA\", \"USA\"]"
]
}
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 0,
"executionTimeMillis" : 22,
"totalKeysExamined" : 20392,
"totalDocsExamined" : 0,
"executionStages" : {
"stage" : "COUNT",
"nReturned" : 0,
"executionTimeMillisEstimate" : 20,
"works" : 20392,
"advanced" : 0,
"needTime" : 20391,
"needYield" : 0,
"saveState" : 159,
"restoreState" : 159,
"isEOF" : 1,
"invalidates" : 0,
"nCounted" : 20305,
"nSkipped" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 20305,
"executionTimeMillisEstimate" : 10,
"works" : 20392,
"advanced" : 20305,
"needTime" : 86,
"needYield" : 0,
"saveState" : 159,
"restoreState" : 159,
"isEOF" : 1,
"invalidates" : 0,
"keyPattern" : {
"imdb.rating" : 1,
"countries" : 1
},
"indexName" : "imdb.rating_1_countries_1",
"isMultiKey" : true,
"multiKeyPaths" : {
"imdb.rating" : [ ],
"countries" : [
"countries"
]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"imdb.rating" : [
"(5.0, inf.0]"
],
"countries" : [
"[\"USA\", \"USA\"]"
]
},
"keysExamined" : 20392,
"seeks" : 87,
"dupsTested" : 20305,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
},
"serverInfo" : {
"host" : "Daniels-MacBook-Pro-3.local",
"port" : 27017,
"version" : "3.6.4",
"gitVersion" : "d0181a711f7e7f39e60b5aeb1dc7097bf6ae5856"
},
"ok" : 1,
"operationTime" : Timestamp(1527013617, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1527013617, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}