[SERVER-67153] Clarify behavior of array traversal in agg expression Created: 09/Jun/22 Updated: 06/Dec/22 |
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| Status: | Backlog |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | None |
| Type: | Improvement | Priority: | Major - P3 |
| Reporter: | Svilen Mihaylov (Inactive) | Assignee: | Backlog - Query Optimization |
| Resolution: | Unresolved | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Assigned Teams: |
Query Optimization
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| Participants: |
| Description |
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Consider the following document:
If it is referred from an agg expression such as [\{$project: {a: "$b.c"}}] then the result (assigned at field "a") will be (unsurprisingly) [2, 3]. Now consider this document which adds extra array nesting:
Currently in classic, the expression returns an empty array [], instead of the more arguably rational result of [[2, 3]] This bug is about clarifying this behavior and specifically determining if it makes sense to adopt it going forward, particularly in the context of the new optimizer. |