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Please see the queries below performed on 2.6.0-rc2. When the query includes a .sort() no records are returned. When the .sort() is removed, the expected records are returned. The .explain() on the sorted version looks quite strange to me. > db.version() 2.6.0-rc2 > db.config.users.find({},{un:1,pe:1,cre:1}) { "_id" : ObjectId("53362b393004cde05e1ae35c"), "un" : "cailin.nelson@10gen.com", "cre" : ISODate("2014-03-29T02:08:57.062Z"), "pe" : "cailin.nelson@10gen.com" } { "_id" : ObjectId("533633aa300495bc76c058cb"), "un" : "cowboy@johnandcailin.com", "cre" : ISODate("2014-03-29T02:44:58.941Z"), "pe" : "cowboy@johnandcailin.com" } { "_id" : ObjectId("533633b2300495bc76c058d1"), "un" : "alberta@johnandcailin.com", "cre" : ISODate("2014-03-29T02:45:06.299Z"), "pe" : "alberta@johnandcailin.com" } > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).sort({cre:-1}).limit(10).skip(0).count() 3 > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).sort({cre:-1}).limit(10).skip(0) > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).sort({cre:-1}).limit(10).skip(0).explain() { "cursor" : "BtreeCursor createdIdx reverse", "isMultiKey" : false, "n" : 0, "nscannedObjects" : 0, "nscanned" : 1, "nscannedObjectsAllPlans" : 0, "nscannedAllPlans" : 1, "scanAndOrder" : false, "indexOnly" : false, "nYields" : 0, "nChunkSkips" : 0, "millis" : 0, "indexBounds" : { "cre" : [ [ /cailin/, /cailin/ ], [ { }, "" ] ] }, "server" : "cailinmac:27017", "filterSet" : false } > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).limit(10).skip(0) { "_id" : ObjectId("533633b2300495bc76c058d1"), "un" : "alberta@johnandcailin.com" } { "_id" : ObjectId("53362b393004cde05e1ae35c"), "un" : "cailin.nelson@10gen.com" } { "_id" : ObjectId("533633aa300495bc76c058cb"), "un" : "cowboy@johnandcailin.com" } > If I downgrade to 2.4.6, then the expected results are returned with the .sort() [scripts] (feature_mmsp_1468)$ mongo MongoDB shell version: 2.4.6 connecting to: test > db.version() 2.4.6 > use mmsdbconfig switched to db mmsdbconfig > db.config.users.find({},{un:1,pe:1,cre:1}) { "_id" : ObjectId("53362b393004cde05e1ae35c"), "un" : "cailin.nelson@10gen.com", "cre" : ISODate("2014-03-29T02:08:57.062Z"), "pe" : "cailin.nelson@10gen.com" } { "_id" : ObjectId("533633aa300495bc76c058cb"), "un" : "cowboy@johnandcailin.com", "cre" : ISODate("2014-03-29T02:44:58.941Z"), "pe" : "cowboy@johnandcailin.com" } { "_id" : ObjectId("533633b2300495bc76c058d1"), "un" : "alberta@johnandcailin.com", "cre" : ISODate("2014-03-29T02:45:06.299Z"), "pe" : "alberta@johnandcailin.com" } > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).sort({cre:-1}).limit(10).skip(0) { "_id" : ObjectId("533633b2300495bc76c058d1"), "un" : "alberta@johnandcailin.com" } { "_id" : ObjectId("533633aa300495bc76c058cb"), "un" : "cowboy@johnandcailin.com" } { "_id" : ObjectId("53362b393004cde05e1ae35c"), "un" : "cailin.nelson@10gen.com" }

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cailin.nelson@10gen.com commented on Mon, 31 Mar 2014 14:17:25 +0000: Thanks! xgen-internal-githook commented on Mon, 31 Mar 2014 14:15:16 +0000: Author: {u'username': u'hkhalsa', u'name': u'Hari Khalsa', u'email': u'hkhalsa@10gen.com'} Message: SERVER-13406 don't extract invalid index assignments from OR subplan when it indexed sorts Branch: v2.6 https://github.com/mongodb/mongo/commit/9de22c408e7080c8c35257302c416ca4941fa0ec xgen-internal-githook commented on Mon, 31 Mar 2014 14:15:14 +0000: Author: {u'username': u'hkhalsa', u'name': u'Hari Khalsa', u'email': u'hkhalsa@10gen.com'} Message: SERVER-13406 add debugging for OR sub-planner Branch: v2.6 https://github.com/mongodb/mongo/commit/eea49e2e48202c8a05d3ffc8b91143d6da2f7126 xgen-internal-githook commented on Mon, 31 Mar 2014 14:14:43 +0000: Author: {u'username': u'hkhalsa', u'name': u'Hari Khalsa', u'email': u'hkhalsa@10gen.com'} Message: SERVER-13406 don't extract invalid index assignments from OR subplan when it indexed sorts Branch: master https://github.com/mongodb/mongo/commit/91b9d4ff3e913f74ee75610db2fa6d448b4df0bf xgen-internal-githook commented on Mon, 31 Mar 2014 14:14:40 +0000: Author: {u'username': u'hkhalsa', u'name': u'Hari Khalsa', u'email': u'hkhalsa@10gen.com'} Message: SERVER-13406 add debugging for OR sub-planner Branch: master https://github.com/mongodb/mongo/commit/5d3070ecd0171700ea30ff7bd698d8b677b50bb6 cailin.nelson@10gen.com commented on Sat, 29 Mar 2014 03:19:00 +0000: > db.version(); 2.6.0-rc2 > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).sort({cre:-1}).limit(10).skip(0).explain(true) { "cursor" : "BtreeCursor createdIdx reverse", "isMultiKey" : false, "n" : 0, "nscannedObjects" : 0, "nscanned" : 1, "nscannedObjectsAllPlans" : 0, "nscannedAllPlans" : 1, "scanAndOrder" : false, "indexOnly" : false, "nYields" : 0, "nChunkSkips" : 0, "millis" : 0, "indexBounds" : { "cre" : [ [ /cailin/, /cailin/ ], [ { }, "" ] ] }, "allPlans" : [ { "cursor" : "BtreeCursor createdIdx reverse", "isMultiKey" : false, "n" : 0, "nscannedObjects" : 0, "nscanned" : 1, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "cre" : [ [ /cailin/, /cailin/ ], [ { }, "" ] ] } } ], "server" : "cailinmac:27017", "filterSet" : false, "stats" : { "type" : "LIMIT", "works" : 2, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "children" : [ { "type" : "PROJECTION", "works" : 1, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "children" : [ { "type" : "FETCH", "works" : 1, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "alreadyHasObj" : 0, "forcedFetches" : 0, "matchTested" : 0, "children" : [ { "type" : "IXSCAN", "works" : 1, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "keyPattern" : "{ cre: 1 }", "boundsVerbose" : "field #0['cre']: [/cailin/, /cailin/], ({}, \"\"]", "isMultiKey" : 0, "yieldMovedCursor" : 0, "dupsTested" : 0, "dupsDropped" : 0, "seenInvalidated" : 0, "matchTested" : 0, "keysExamined" : 1, "children" : [ ] } ] } ] } ] } } > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]},{un:1}).limit(10).skip(0).explain(true) { "clauses" : [ { "cursor" : "BtreeCursor usernameIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "un" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } }, { "cursor" : "BtreeCursor primaryEmailIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "pe" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } } ], "cursor" : "QueryOptimizerCursor", "n" : 3, "nscannedObjects" : 6, "nscanned" : 6, "nscannedObjectsAllPlans" : 6, "nscannedAllPlans" : 6, "scanAndOrder" : false, "nYields" : 0, "nChunkSkips" : 0, "millis" : 0, "allPlans" : [ { "clauses" : [ { "cursor" : "BtreeCursor usernameIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "un" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } }, { "cursor" : "BtreeCursor primaryEmailIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "pe" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } } ], "cursor" : "QueryOptimizerCursor", "n" : 3, "nscannedObjects" : 6, "nscanned" : 6, "scanAndOrder" : false, "nChunkSkips" : 0 } ], "server" : "cailinmac:27017", "filterSet" : false, "stats" : { "type" : "LIMIT", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 4, "needFetch" : 0, "isEOF" : 1, "children" : [ { "type" : "PROJECTION", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "children" : [ { "type" : "FETCH", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 4, "needFetch" : 0, "isEOF" : 1, "alreadyHasObj" : 0, "forcedFetches" : 0, "matchTested" : 0, "children" : [ { "type" : "OR", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 4, "needFetch" : 0, "isEOF" : 1, "dupsTested" : 6, "dupsDropped" : 3, "locsForgotten" : 0, "matchTested_0" : 0, "matchTested_1" : 0, "children" : [ { "type" : "IXSCAN", "works" : 4, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "keyPattern" : "{ un: 1 }", "boundsVerbose" : "field #0['un']: [\"\", {}), [/cailin/, /cailin/]", "isMultiKey" : 0, "yieldMovedCursor" : 0, "dupsTested" : 0, "dupsDropped" : 0, "seenInvalidated" : 0, "matchTested" : 3, "keysExamined" : 3, "children" : [ ] }, { "type" : "IXSCAN", "works" : 4, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "keyPattern" : "{ pe: 1 }", "boundsVerbose" : "field #0['pe']: [\"\", {}), [/cailin/, /cailin/]", "isMultiKey" : 0, "yieldMovedCursor" : 0, "dupsTested" : 0, "dupsDropped" : 0, "seenInvalidated" : 0, "matchTested" : 3, "keysExamined" : 3, "children" : [ ] } ] } ] } ] } ] } } > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]}).sort({cre:-1}).limit(10).skip(0).explain(true) { "cursor" : "BtreeCursor createdIdx reverse", "isMultiKey" : false, "n" : 0, "nscannedObjects" : 0, "nscanned" : 1, "nscannedObjectsAllPlans" : 0, "nscannedAllPlans" : 1, "scanAndOrder" : false, "indexOnly" : false, "nYields" : 0, "nChunkSkips" : 0, "millis" : 0, "indexBounds" : { "cre" : [ [ /cailin/, /cailin/ ], [ { }, "" ] ] }, "allPlans" : [ { "cursor" : "BtreeCursor createdIdx reverse", "isMultiKey" : false, "n" : 0, "nscannedObjects" : 0, "nscanned" : 1, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "cre" : [ [ /cailin/, /cailin/ ], [ { }, "" ] ] } } ], "server" : "cailinmac:27017", "filterSet" : false, "stats" : { "type" : "LIMIT", "works" : 2, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "children" : [ { "type" : "FETCH", "works" : 1, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "alreadyHasObj" : 0, "forcedFetches" : 0, "matchTested" : 0, "children" : [ { "type" : "IXSCAN", "works" : 1, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 0, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "keyPattern" : "{ cre: 1 }", "boundsVerbose" : "field #0['cre']: [/cailin/, /cailin/], ({}, \"\"]", "isMultiKey" : 0, "yieldMovedCursor" : 0, "dupsTested" : 0, "dupsDropped" : 0, "seenInvalidated" : 0, "matchTested" : 0, "keysExamined" : 1, "children" : [ ] } ] } ] } } > db.config.users.find({$or:[{un: /cailin/},{pe:/cailin/}]}).limit(10).skip(0).explain(true) { "clauses" : [ { "cursor" : "BtreeCursor usernameIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "un" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } }, { "cursor" : "BtreeCursor primaryEmailIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "pe" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } } ], "cursor" : "QueryOptimizerCursor", "n" : 3, "nscannedObjects" : 6, "nscanned" : 6, "nscannedObjectsAllPlans" : 6, "nscannedAllPlans" : 6, "scanAndOrder" : false, "nYields" : 0, "nChunkSkips" : 0, "millis" : 0, "allPlans" : [ { "clauses" : [ { "cursor" : "BtreeCursor usernameIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "un" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } }, { "cursor" : "BtreeCursor primaryEmailIdx", "isMultiKey" : false, "n" : 3, "nscannedObjects" : 3, "nscanned" : 3, "scanAndOrder" : false, "indexOnly" : false, "nChunkSkips" : 0, "indexBounds" : { "pe" : [ [ "", { } ], [ /cailin/, /cailin/ ] ] } } ], "cursor" : "QueryOptimizerCursor", "n" : 3, "nscannedObjects" : 6, "nscanned" : 6, "scanAndOrder" : false, "nChunkSkips" : 0 } ], "server" : "cailinmac:27017", "filterSet" : false, "stats" : { "type" : "LIMIT", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 4, "needFetch" : 0, "isEOF" : 1, "children" : [ { "type" : "FETCH", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 4, "needFetch" : 0, "isEOF" : 1, "alreadyHasObj" : 0, "forcedFetches" : 0, "matchTested" : 0, "children" : [ { "type" : "OR", "works" : 8, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 4, "needFetch" : 0, "isEOF" : 1, "dupsTested" : 6, "dupsDropped" : 3, "locsForgotten" : 0, "matchTested_0" : 0, "matchTested_1" : 0, "children" : [ { "type" : "IXSCAN", "works" : 4, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "keyPattern" : "{ un: 1 }", "boundsVerbose" : "field #0['un']: [\"\", {}), [/cailin/, /cailin/]", "isMultiKey" : 0, "yieldMovedCursor" : 0, "dupsTested" : 0, "dupsDropped" : 0, "seenInvalidated" : 0, "matchTested" : 3, "keysExamined" : 3, "children" : [ ] }, { "type" : "IXSCAN", "works" : 4, "yields" : 0, "unyields" : 0, "invalidates" : 0, "advanced" : 3, "needTime" : 0, "needFetch" : 0, "isEOF" : 1, "keyPattern" : "{ pe: 1 }", "boundsVerbose" : "field #0['pe']: [\"\", {}), [/cailin/, /cailin/]", "isMultiKey" : 0, "yieldMovedCursor" : 0, "dupsTested" : 0, "dupsDropped" : 0, "seenInvalidated" : 0, "matchTested" : 3, "keysExamined" : 3, "children" : [ ] } ] } ] } ] } } > scotthernandez commented on Sat, 29 Mar 2014 03:14:00 +0000: Please include the explain in verbose mode (pass in true/1) for: with/out sort query without the projection http://docs.mongodb.org/manual/reference/method/cursor.explain/

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