[SERVER-32822] Support reading from unique indexes with mixed version keys Created: 22/Jan/18  Updated: 30/Oct/23  Resolved: 01/Mar/18

Status: Closed
Project: Core Server
Component/s: Storage
Affects Version/s: None
Fix Version/s: 3.7.3

Type: Improvement Priority: Major - P3
Reporter: Alexander Gorrod Assignee: Neha Khatri
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
depends on SERVER-32821 Support rolling upgrade to new unique... Closed
Backwards Compatibility: Fully Compatible
Sprint: Storage 2018-02-26, Storage Non-NYC 2018-03-12
Participants:

 Description   

With the addition of a new index format that maintains compatibility with the previous format, read operations will need to be able to determine which format an entry in the index uses and return the correct result.



 Comments   
Comment by Githook User [ 01/Mar/18 ]

Author:

{'email': 'neha.khatr@mongodb.com', 'name': 'nehakhatri5'}

Message: SERVER-32822 Support read from unique index with both old and new format entries

During rolling upgrades the existing unique indexes' version would be changed
without translating the existing data to the new format. With an index in this
state, new data can be inserted in new format. When reading from such an index,
use the correct read logic based on the format of the entry being read.

In doing so, filter the key from the KeyString to obtain size of the Index Key.
Index Key size would indicate that whether the key is old format or new format.
Branch: master
https://github.com/mongodb/mongo/commit/9960da7396adf3a92ac22e3c0fc62be1bc54be91

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