$match on shard key + $group on non-shard key should be distinct scan eligible

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    • Type: Task
    • Resolution: Unresolved
    • Priority: Major - P3
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      On a sharded collection,

      coll.createIndex({shardKey: 1, notShardKey: 1})
coll.explain().aggregate([
  {$match: {shardKey: {$gte: "foo"}}}, 
  {$group: {_id: "$notShardKey"}}
])

      seems to result in an IXSCAN, even though a DISTINCT_SCAN on could be used. The equivalent distinct() command results in a DISTINCT_SCAN.

              Assignee:
              Unassigned
              Reporter:
              Henri Nikku
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                Created:
                Updated: