[SERVER-34613] aggregation pipeline operators for array iterations like permutations and k combinations Created: 23/Apr/18 Updated: 04/Sep/18 Resolved: 30/Jul/18 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Aggregation Framework |
| Affects Version/s: | 3.6.4 |
| Fix Version/s: | None |
| Type: | New Feature | Priority: | Major - P3 |
| Reporter: | Sean Watford | Assignee: | William Byrne III |
| Resolution: | Incomplete | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Participants: |
| Description |
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Currently no operations allow for combinations or permutations of grouped fields within the aggregation pipeline. MapReduce currently doesn't support multiple values returned as part of "reduce", so it's not an option at this point. However, it would best to have this implemented as part of the aggregation pipeline so that other operations can be chained like sorting. |
| Comments |
| Comment by Asya Kamsky [ 30/Jul/18 ] |
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Closing as it's not clear what exactly would satisfy this feature request. swatford please re-open if you can provide more details, preferably with an example of input documents and result documents that are desired. |
| Comment by William Byrne III [ 14/Jun/18 ] |
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Hi Sean, I am familiar with the basic mathematical uses of the terms k-combinations and permutations (as detailed in this wikipedia article) - both are selections of items from a set, but with permutations the order selected is significant. Using existing MongoDB operators you can generate permutations of a set of array members, but I am not clear on what you mean by "combinations or permutations of grouped fields". Please clarify exactly what it is you are seeking to have these proposed new operators do. If you could provide sample input documents and what the outputs should look like then we will be better able to investigate this further for you. Regards, William Byrne III |