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Type:
Bug
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Resolution: Fixed
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Priority:
Critical - P2
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Affects Version/s: 4.1.8
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Component/s: Aggregation Framework
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None
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Fully Compatible
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ALL
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Query 2019-03-25, Query 2019-04-08
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Looks like DISTINCT_SCAN added in SERVER-9507 doesn't request the full document like it does correctly individual fields.
// correct
db.newTest.aggregate([
{$sort:{valueDate:1}},
{$group:{_id: "$valueDate", first: {$first: "$farmId"}}}
])
{ "_id" : ISODate("2019-01-01T00:00:00Z"), "first" : 3 }
{ "_id" : ISODate("2019-02-01T00:00:00Z"), "first" : 1 }
//incorrect
db.newTest.aggregate([
{$sort:{valueDate:1}},
{$group:{_id: "$valueDate", first: {$first: "$$ROOT"}}}
])
{ "_id" : ISODate("2019-01-01T00:00:00Z"), "first" : { "valueDate" : ISODate("2019-01-01T00:00:00Z") } }
{ "_id" : ISODate("2019-02-01T00:00:00Z"), "first" : { "valueDate" : ISODate("2019-02-01T00:00:00Z") } }