[SERVER-2166] Support 2 or more input collections for M/R Created: 01/Dec/10  Updated: 01/Dec/10  Resolved: 01/Dec/10

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Alvin Richards (Inactive) Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
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Duplicate
duplicates SERVER-647 M/R: reduce into existing collection Closed
Participants:

 Description   

Requirement as defined by customer:

1. We have collection that contains all documents that are to be processed.
2. At point of time, we will consider this collection as archive, and we will go ahead and create a new collection. But the documents pending processing in previous collection needs to be moved over to new collection. However in current releases, we don't have mechanism to move the documents in a sharded environment in backend itself. (One of the request that we have asked for).
3. So, under these conditions, it will be useful to do a map reduce on more than one collection.



 Comments   
Comment by Eliot Horowitz (Inactive) [ 01/Dec/10 ]

You would use
merge if each collection had disjoint keys
reduce if you have the same keys in multiple collections.

If the docs aren't clear, please either make a note or fix.

Comment by Eliot Horowitz (Inactive) [ 01/Dec/10 ]

See SERVER-647 and http://www.mongodb.org/display/DOCS/MapReduce#MapReduce-outType

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