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Type:
Task
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Resolution: Unresolved
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: None
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Query Optimization
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{$group: {_id: "$shardKey", accum: {$bottom: {sortBy: {notShardKey: 1}, output: "$shardKey"}}}}
results in a COLLSCAN when ran on a collection with a compound index on shardKey and notShardKey.
It looks like the issue here is that when we check if a sort can be provided by an index, we don't account for the distinct key. Normally the sort spec would have to be a prefix of the index key, but for queries like this, the index key prefix we want is actually `{...distinctKey, ...sortSpec}`.
- related to
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SERVER-29444 Use a covered and streaming plan for $group, $sum:1 queries
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- Backlog
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- Needs Scheduling
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