Optimize $group on meta $min/$max on measurements for time-series collections

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    • Type: Improvement
    • Resolution: Fixed
    • Priority: Major - P3
    • 5.0.0-rc0
    • Affects Version/s: None
    • Component/s: Query Planning
    • None
    • Fully Compatible
    • Query Optimization 2021-05-03
    • None
    • 3
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      For a time-series collection, we automatically bucket fields and have a control block with the min and max of each, like so: 

      { _id: ObjectId(...),
  control: { 
    version: 1, // in case we want to change the format in a later release
    min: { _id: ..., time: ISODate("2020-09-09T16:54:04.174Z"), field0: 0.01, ... },
    max: { _id: ..., time: ISODate("2020-09-09T16:54:04.450Z"), field0: 0.99, ... },
  },
  meta: ...,
  data: { _id: { 0:..., 1: ..., ...},
          time: { 0: ISODate("2020-09-09T16:54:04.174Z"),
                  1: ISODate("2020-09-09T16:54:04.450Z"), ...}, 
          field0: { 0: 0.99, 1: 0.01,...},
          field1: { 2: "high", 42: "low",...}, // Missing fields are omitted
          ...}
}

      For a query over that collection like this:

      db.example.aggregate([{$group: {_id: "$meta.x", field0: {$max: "$field0"}}}])

      We should be able to avoid unpacking or looking at "data" at all.

              Assignee:
              Svilen Mihaylov (Inactive)
              Reporter:
              Charlie Swanson
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                Created:
                Updated:
                Resolved: