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  1. Core Server
  2. SERVER-28195

$skip followed by $limit in aggregation resort & lost records when $sort by equal values

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    • Type: Icon: Bug Bug
    • Resolution: Works as Designed
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: 3.4.1
    • Component/s: Aggregation Framework
    • Labels:
      None
    • Environment:
      targetMinOS: Windows 7/Windows Server 2008 R2
      db version v3.4.1
      git version: 5e103c4f5583e2566a45d740225dc250baacfbd7
    • ALL
    • Hide 
      > db.issue.find()

      { "_id" : ObjectId("58b3d25422ad9b04484145f9"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0227T07:16:36.173Z"), "likes" : [ ObjectId("589d65ac10ee7a29a08e022a") ], "visible" : 1,"country" : ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "инструкция", "caption" : "Заголовок" }, "requireModeration" : 1, "rating" : 0 }
{ "_id" : ObjectId("58b3d25d22ad9b04484145fa"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0227T07:16:45.772Z"), "likes" : [ ], "visible" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "инструкция22", "caption": "Заголовок 22" }, "requireModeration" : 1, "rating" : 0 }
{ "_id" : ObjectId("58b3d2d122ad9b04484145fb"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0227T07:18:41.065Z"), "likes" : [ ObjectId("589d65ac10ee7a29a08e022a") ], "visible" : 1,"country" : ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "что-то", "caption" : "Ииииха" }, "requireModeration" : 1, "rating" : 0 }
{ "_id" : ObjectId("58b9656e905c7a279806f8f6"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T12:45:34.161Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "йцуйцу", "caption" :"йцуйцу" }, "rating" : 0 }
{ "_id" : ObjectId("58b96575905c7a279806f8f7"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T12:45:41.038Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "йцуйцу11", "caption" :"йцуйцуй11" }, "rating" : 0 }
{ "_id" : ObjectId("58b96578905c7a279806f8f8"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T12:45:44.677Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "йцуйцу1122", "caption" :"йцуйцуй1122" }, "rating" : 0 }
{ "_id" : ObjectId("58b96e44905c7a279806f8f9"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T13:23:16.176Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "text", "caption" : "Title" }, "rating" : 10 }
      Show
      > db.issue.find() { "_id" : ObjectId("58b3d25422ad9b04484145f9"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0227T07:16:36.173Z"), "likes" : [ ObjectId("589d65ac10ee7a29a08e022a") ], "visible" : 1,"country" : ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "инструкция", "caption" : "Заголовок" }, "requireModeration" : 1, "rating" : 0 } { "_id" : ObjectId("58b3d25d22ad9b04484145fa"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0227T07:16:45.772Z"), "likes" : [ ], "visible" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "инструкция22", "caption": "Заголовок 22" }, "requireModeration" : 1, "rating" : 0 } { "_id" : ObjectId("58b3d2d122ad9b04484145fb"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0227T07:18:41.065Z"), "likes" : [ ObjectId("589d65ac10ee7a29a08e022a") ], "visible" : 1,"country" : ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "что-то", "caption" : "Ииииха" }, "requireModeration" : 1, "rating" : 0 } { "_id" : ObjectId("58b9656e905c7a279806f8f6"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T12:45:34.161Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "йцуйцу", "caption" :"йцуйцу" }, "rating" : 0 } { "_id" : ObjectId("58b96575905c7a279806f8f7"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T12:45:41.038Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "йцуйцу11", "caption" :"йцуйцуй11" }, "rating" : 0 } { "_id" : ObjectId("58b96578905c7a279806f8f8"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T12:45:44.677Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "йцуйцу1122", "caption" :"йцуйцуй1122" }, "rating" : 0 } { "_id" : ObjectId("58b96e44905c7a279806f8f9"), "author" :ObjectId("589d65ac10ee7a29a08e022a"), "type" : "customs", "date" : ISODate("2017-0303T13:23:16.176Z"), "likes" : [ ], "visible" : 1, "requireModeration" : 1, "country" :ObjectId("58a1a0bdc98ea02284fe077b"), "guideBody" : { "text" : "text", "caption" : "Title" }, "rating" : 10 }

      Seems, issue exists only when you $sort records having equal value (rating here)

      >db.issue.aggregate( [ 
{ '$match':       { country: ObjectId("58a1a0bdc98ea02284fe077b"),        visible: 1,        type: 'customs' } },  
{ '$sort': { rating: -1 } },   
{ '$project': {_id:1}}
]);

      { "_id" : ObjectId("58b96e44905c7a279806f8f9") }
{ "_id" : ObjectId("58b3d25422ad9b04484145f9") }
{ "_id" : ObjectId("58b3d25d22ad9b04484145fa") }
{ "_id" : ObjectId("58b3d2d122ad9b04484145fb") }
{ "_id" : ObjectId("58b9656e905c7a279806f8f6") }
{ "_id" : ObjectId("58b96575905c7a279806f8f7") }
{ "_id" : ObjectId("58b96578905c7a279806f8f8") }

      > db.issue.aggregate( [ 
{ '$match':       { country: ObjectId("58a1a0bdc98ea02284fe077b"),        visible: 1,        type: 'customs' } },   
{ '$sort': { rating: -1 } },   
{ '$project': {_id:1}},   
*{ '$skip': 0 },   
{ '$limit': 5 } *
] );

      { "_id" : ObjectId("58b96e44905c7a279806f8f9") }
{ "_id" : ObjectId("58b9656e905c7a279806f8f6") }
{ "_id" : ObjectId("58b96575905c7a279806f8f7") }
{ "_id" : ObjectId("58b3d25d22ad9b04484145fa") }
{ "_id" : ObjectId("58b3d25422ad9b04484145f9") }

      here we:

      • have resorted results
      • lost * { "_id" : ObjectId("58b3d2d122ad9b04484145fb") }

        *

      there is no this record on next 5

      >db.issue.aggregate( [
{ '$match':       { country: ObjectId("58a1a0bdc98ea02284fe077b"),        visible: 1,        type: 'customs' } },   
{ '$sort': { rating: -1 } },   
{ '$project': {_id:1}},  
{ '$skip': 5 },   
{ '$limit': 5 } 
] );

      { "_id" : ObjectId("58b96575905c7a279806f8f7") }
{ "_id" : ObjectId("58b96578905c7a279806f8f8") }

        1. test-28195.js
          4 kB

            Assignee:
            kelsey.schubert@mongodb.com Kelsey Schubert
            Reporter:
            trueshura Alexandr
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            0 Vote for this issue
            Watchers:
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              Created:
              Updated:
              Resolved: