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Type:
Question
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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: 3.2.17
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Component/s: Index Maintenance
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None
The partial filter expression contains a scalar equality expression : "bool" : true
db.coll.getIndexes()
[
...
{
"v" : 1,
"key" : {
"timestamp" : 1,
"userId" : 1
},
"name" : "timestamp_1_userId_1",
"ns" : "...",
"background" : true,
"partialFilterExpression" : {
"bool" : true
}
}
]
A query contains the index fields, projects the index field and uses the single possible value for the partial expression:
db.coll.explain("executionStats").find({ timestamp: { $gte: 1511041284 }, userId: { $in: [ 1,2,3,4 ]}, bool: true },{timestamp: 1, userId:1, _id:0 }) { ... "executionStats" : { "executionSuccess" : true, "nReturned" : 2, "executionTimeMillis" : 14, "totalKeysExamined" : 294, "totalDocsExamined" : 2, "executionStages" : { "stage" : "PROJECTION", "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 296, "advanced" : 2, "needTime" : 292, "needYield" : 0, "saveState" : 4, "restoreState" : 4, "isEOF" : 1, "invalidates" : 0, "transformBy" : { "timestamp" : 1, "userId" : 1, "_id" : 0 }, "inputStage" : { "stage" : "FETCH", "filter" : { "bool" : { "$eq" : true } }, "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 296, "advanced" : 2, "needTime" : 292, "needYield" : 0, "saveState" : 4, "restoreState" : 4, "isEOF" : 1, "invalidates" : 0, "docsExamined" : 2, "alreadyHasObj" : 0, "inputStage" : { "stage" : "IXSCAN", "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 295, "advanced" : 2, "needTime" : 292, "needYield" : 0, "saveState" : 4, "restoreState" : 4, "isEOF" : 1, "invalidates" : 0, "keyPattern" : { "timestamp" : 1, "userId" : 1 }, "indexName" : "timestamp_1_userId_1", "isMultiKey" : false, "isUnique" : false, "isSparse" : false, "isPartial" : true, "indexVersion" : 1, "direction" : "forward", "indexBounds" : { "timestamp" : [ "[1511041284.0, inf.0]" ], "userId" : [ ...
Under such conditions, shouldn't it be enough for the index to cover the query?
- duplicates
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SERVER-28889 Partial index shouldn't do fetch on conditions that are true by the definition of the index
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- Closed
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