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  1. Core Server
  2. SERVER-74302

issues with GROUP_BY stage in aggregation (6.2.0)

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    • Type: Icon: Bug Bug
    • Resolution: Gone away
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: None
    • Labels:
      None
    • Query Optimization
    • ALL
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      example data:

       

      [
{ metadata: { testId: "foo", publicFacetLabels: {difficulty: "easy"}, score: 2 } },
{ metadata: { testId: "foo", publicFacetLabels: {difficulty: "easy"}, score: 2 } },
{ metadata: { testId: "foo", publicFacetLabels: {difficulty: "easy"}, score: 2 } },
{ metadata: { testId: "foo", publicFacetLabels: {difficulty: "hard"}, score: 2 } },
{ metadata: { testId: "foo", publicFacetLabels: {difficulty: "hard"}, score: 2 } },
]

      Execute pipeline:

      [{
 $match: {
  'metadata.testId': 'foo'
 }
}, {
 $group: {
  _id: {
   difficulty: '$metadata.publicFacetLabels.difficulty'
  },
  responseCount: {
 $count: {}
  },
  sumScore: {
   $sum: '$metadata.score'
  }
 }
}, {
 $project: {
  _id: 0,
  sumScore: 1,
  responseCount: 1,
  difficulty: '$_id.difficulty'
 }
}]

      Expected Result:

      [
{difficulty: "easy", sumScore: 6, responseCount: 3},
{difficulty: "hard", sumScore: 4, responseCount: 2}
]

       

      Show
      example data:   [ { metadata: { testId: "foo" , publicFacetLabels: {difficulty: "easy" }, score: 2 } }, { metadata: { testId: "foo" , publicFacetLabels: {difficulty: "easy" }, score: 2 } }, { metadata: { testId: "foo" , publicFacetLabels: {difficulty: "easy" }, score: 2 } }, { metadata: { testId: "foo" , publicFacetLabels: {difficulty: "hard" }, score: 2 } }, { metadata: { testId: "foo" , publicFacetLabels: {difficulty: "hard" }, score: 2 } }, ] Execute pipeline: [{  $match: {   'metadata.testId' : 'foo'  } }, {  $group: {   _id: {    difficulty: '$metadata.publicFacetLabels.difficulty'   },   responseCount: {  $count: {}   },   sumScore: {    $sum: '$metadata.score'   }  } }, {  $project: {   _id: 0,   sumScore: 1,   responseCount: 1,   difficulty: '$_id.difficulty'  } }] Expected Result: [ {difficulty: "easy" , sumScore: 6, responseCount: 3}, {difficulty: "hard" , sumScore: 4, responseCount: 2} ]  
    • QO 2023-04-03

      I have pipelines that previously worked but no longer do since upgrading to 6.2.0. They all specifically have a GROUP_BY stage that is no longer working as expected. e.g.

      [{
 $match: {
  'metadata.testId': 'foo'
 }
}, {
 $group: {
  _id: {
   difficulty: '$metadata.publicFacetLabels.difficulty'
  },
  responseCount: {
   $count: {}
  },
  sumScore: {
   $sum: '$metadata.score'
  }
 }
}, {
 $project: {
  _id: 0,
  sumScore: 1,
  responseCount: 1,
  difficulty: '$_id.difficulty'
 }
}]

      In the above example I was previously getting the following result

       

      {
 responseCount:166,       
 sumScore: 150,
 difficulty: "Hard"
}

      Since updating to version 6.2.0 I am getting:

       

      {
sumScore: 150,
} 

      Note: these pipelines are being run against a timeseries collection

       
       

            Assignee:
            milena.ivanova@mongodb.com Milena Ivanova
            Reporter:
            john@synap.ac John Anderson
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            Watchers:
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              Created:
              Updated:
              Resolved: