Why compound wildcard index still do fetch?

Working with Data
, , ,
5

Hi @steevej ,

Thanks for your advice.

I modified the aggregation script:

[
  {
    $match: {
      year: 2024,
      month: 8,
      day: 1,
      "attributes.country": {$ne: null},
    }
  },
  {
    $group: {
      _id: {
        appId: "$appId",
        os: "$os",
        country: "$attributes.country",
      },
      value: {
        $sum: 1
      }
    }
  }
]

But it still uses fetch.

image
image1902×942 92.5 KB

{
 "stage": "FETCH",
 "planNodeId": 2,
 "nReturned": 180895,
 "executionTimeMillisEstimate": 1762,
 "opens": 1,
 "closes": 1,
 "saveState": 696,
 "restoreState": 696,
 "isEOF": 1,
 "numTested": 180895,
 "filter": {
  "attributes.country": {
   "$not": {
    "$eq": null
   }
  }
 },
 "docsExamined": 180895,
 "keysExamined": 0
}

Very strange.