[SERVER-19829] Replace MurmurHash for text index v3 Created: 07/Aug/15  Updated: 19/Sep/15  Resolved: 24/Aug/15

Status: Closed
Project: Core Server
Component/s: Text Search
Affects Version/s: 3.1.6
Fix Version/s: 3.1.8

Type: Bug Priority: Major - P3
Reporter: Adam Chelminski (Inactive) Assignee: Mark Benvenuto
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Backwards Compatibility: Fully Compatible
Operating System: ALL
Sprint: Platform 8 08/28/15
Participants:

 Description   

MurmurHash is unstable, so text index v3 needs to use a new hash function. This MUST be completed before text index v3 is released in a stable version of MongoDB.



 Comments   
Comment by Githook User [ 24/Aug/15 ]

Author:

{u'username': u'markbenvenuto', u'name': u'Mark Benvenuto', u'email': u'mark.benvenuto@mongodb.com'}

Message: SERVER-19829: Use MD5 and longer key prefixes in text index v3 for long terms.
Branch: master
https://github.com/mongodb/mongo/commit/1535c4b38a408f8d53c02dce51aaca916a02472d

Comment by Mark Benvenuto [ 12/Aug/15 ]

Since we want a hash function that is
1. stable (i.e., not implementation defined)
2. portable (i.e., endian safe)

We have decided to use MD5 since we already use it in dbhash.

Also, we have decided to changed the threshold from 32 bytes to at least 128 bytes for these keys.

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