[DOCS-1901] note that users do not need to compute hash values for hashed shard key values. Created: 09/Sep/13  Updated: 11/Jan/17  Resolved: 17/Sep/13

Status: Closed
Project: Documentation
Component/s: None
Affects Version/s: None
Fix Version/s: 01112017-cleanup

Type: Task Priority: Major - P3
Reporter: Kelly Stirman Assignee: Bob Grabar
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:
Days since reply: 10 years, 22 weeks, 1 day ago

 Description   

This entry in the manual: http://docs.mongodb.org/manual/reference/command/findAndModify/

at the end says "Warning When using findAndModify in a sharded environment, the query must contain the shard key for all operations against the shard cluster. findAndModify operations issued against mongos instances for non-sharded collections function normally."

We could specify that when using a hashed index simply specify the _id value, and/or we could modify this page: http://docs.mongodb.org/manual/tutorial/create-a-hashed-index/

Unsure if other pages may need to be updated.



 Comments   
Comment by auto [ 17/Sep/13 ]

Author:

{u'username': u'bgrabar', u'name': u'Bob Grabar', u'email': u'bob.grabar@10gen.com'}

Message: DOCS-1901 users need not compute hash values for hashed shard key

Signed-off-by: Sam Kleinman <samk@10gen.com>
Branch: master
https://github.com/mongodb/docs/commit/c7b095de30a455d8b4f8b875299392f40f1a5608

Comment by Bob Grabar [ 17/Sep/13 ]

Viewable in github:
https://github.com/bgrabar/docs-mongodb/commit/e436ba6db75d5a226044c523209eeb4bfb7fa182

Comment by Sam Kleinman (Inactive) [ 09/Sep/13 ]

actionable: add note to the hashed sharding section that mongodb automatically hashes the shard key, and applications do not need to hash keys before issuing read or write oeprations to the server.

Comment by Kelly Stirman [ 09/Sep/13 ]

Agree that _id is irrelevant, my mistake.

Still, a user could be confused to think they need to hash the shard key for findAndModify when using a hashed shard key. See https://groups.google.com/d/msg/mongodb-masters/lrSE6q8NGuM/t5zpE-OOH30J

Comment by Sam Kleinman (Inactive) [ 09/Sep/13 ]

The _id field is not necessarily related to the hashed shard key, which might be of any field in the document.

Comment by Scott Hernandez (Inactive) [ 09/Sep/13 ]

A shard key is a shard key. We should not say anything unless there is something special to say and in this case there isn't.

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