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Type:
Task
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Resolution: Done
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Priority:
Minor - P4
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Affects Version/s: None
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Component/s: manual
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Labels:
There have been a few behavior changes in v2.6 related to negations. These should probably go into the 2.6 release notes? See SERVER-13324 and SERVER-12532 or come talk to me for details.
1) In 2.4 it is possible to get different results for negations depending on whether or not an indexed plan is used:
> t.drop() true > t.save({a: 1}) > t.save({b: 1}) > t.find({a: {$not: {$gt: 3}}}) { "_id" : ObjectId("5330803029b74d493d375e46"), "a" : 1 } { "_id" : ObjectId("5330803529b74d493d375e47"), "b" : 1 } > t.ensureIndex({a: 1}) > t.find({a: {$not: {$gt: 3}}}) { "_id" : ObjectId("5330803029b74d493d375e46"), "a" : 1 }
In 2.6, the results will always be the same regardless of whether or not there is an index:
> t.drop() true > t.save({a: 1}) WriteResult({ "nInserted" : 1 }) > t.save({b: 1}) WriteResult({ "nInserted" : 1 }) > t.find({a: {$not: {$gt: 3}}}) { "_id" : ObjectId("5330808b3a40985f27706d1e"), "a" : 1 } { "_id" : ObjectId("5330808d3a40985f27706d1f"), "b" : 1 } > t.ensureIndex({a: 1}) { "createdCollectionAutomatically" : false, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > t.find({a: {$not: {$gt: 3}}}) { "_id" : ObjectId("5330808d3a40985f27706d1f"), "b" : 1 } { "_id" : ObjectId("5330808b3a40985f27706d1e"), "a" : 1 }
2) Negation predicates will no longer use sparse indices. This is necessary in order to preserve the invariant from (1), namely that a negation query should return the same results for indexed and unindexed plans. See SERVER-13324.
- is related to
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SERVER-12532 Negate index bounds for $not instead of defaulting to a collection scan
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- Closed
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- Closed
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