Details
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Bug
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Resolution: Fixed
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Critical - P2
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3.6.0-rc0
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None
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Fully Compatible
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ALL
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Query 2017-11-13
Description
The optimization added in SERVER-27115 to allow index usage in the case of a renamed field is broken for matches on a dotted field path. See the example below. This is a regression introduced during 3.5 development. The 3.6 release candidates are affected, but no pre-existing stable release series is affected.
> db.c.drop();
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true
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> db.c.insert({x: [{y: 1}, {y: 2}]});
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WriteResult({ "nInserted" : 1 })
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// Match with no dotted field path returns the correct result. The explain indicates that
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// the $match stage swapped in front of the $addFields, and was absorbed into the
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// $cursor stage after being correctly renamed to a match on "x".
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> db.c.aggregate([{$addFields: {z: "$x"}}, {$match: {z: {y: 1}}}]);
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{ "_id" : ObjectId("59ef5d62b49385b9971e2c09"), "x" : [ { "y" : 1 }, { "y" : 2 } ], "z" : [ { "y" : 1 }, { "y" : 2 } ] }
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> db.c.explain().aggregate([{$addFields: {z: "$x"}}, {$match: {z: {y: 1}}}]);
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{
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"stages" : [
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{
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"$cursor" : {
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"query" : {
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"x" : {
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"$eq" : {
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"y" : 1
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}
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}
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},
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"queryPlanner" : {
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"plannerVersion" : 1,
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"namespace" : "test.c",
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"indexFilterSet" : false,
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"parsedQuery" : {
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"x" : {
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"$eq" : {
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"y" : 1
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}
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}
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},
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"winningPlan" : {
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"stage" : "COLLSCAN",
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"filter" : {
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"x" : {
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"$eq" : {
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"y" : 1
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}
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}
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},
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"direction" : "forward"
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},
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"rejectedPlans" : [ ]
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}
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}
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},
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{
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"$addFields" : {
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"z" : "$x"
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}
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}
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],
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"ok" : 1
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}
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// When a similar match is expressed using the dotted path "z.y", the matching document
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// is incorrectly omitted from the result set. The explain indicates that the rename to "x.y"
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// was not applied correctly.
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> db.c.explain().aggregate([{$addFields: {z: "$x"}}, {$match: {"z.y": 1}}]);
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{
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"stages" : [
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{
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"$cursor" : {
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"query" : {
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"z.y" : {
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"$eq" : 1
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}
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},
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"queryPlanner" : {
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"plannerVersion" : 1,
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"namespace" : "test.c",
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"indexFilterSet" : false,
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"parsedQuery" : {
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"z.y" : {
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"$eq" : 1
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}
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},
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"winningPlan" : {
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"stage" : "COLLSCAN",
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"filter" : {
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"z.y" : {
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"$eq" : 1
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}
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},
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"direction" : "forward"
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},
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"rejectedPlans" : [ ]
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}
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}
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},
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{
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"$addFields" : {
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"z" : "$x"
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}
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}
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],
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"ok" : 1
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}
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Attachments
Issue Links
- is caused by
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- Closed
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- related to
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- Closed
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