[SERVER-57794] Implement run-length-encoding in Simple-8b Created: 17/Jun/21  Updated: 29/Oct/23  Resolved: 22/Jul/21

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: 5.1.0-rc0

Type: Task Priority: Major - P3
Reporter: Henrik Edin Assignee: Jackson Xie (Inactive)
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
depends on SERVER-57318 Simple-8b encoder/decoder Closed
Backwards Compatibility: Fully Compatible
Sprint: Execution Team 2021-07-12, Execution Team 2021-07-26
Participants:

 Description   

In an unused Simple-8b selector slot (number 15) let the remaining 4 bits of the first byte in a Simple-8b block represent a RLE count. 

This count should be treated as a repeat of the previous value multiplied with 120.

The encoder may have to look back several written Simple-8b blocks and re-write as RLE.

A repeat of 119 needs the following Simple-8b blocks:

#1 <60 buckets>
#2 <30 buckets>
#3 <20 buckets>
#7 <8 buckets>
#14 <1 bucket>

When the 120th identical value is appended they can all be replaced by RLE selector #15 with count=1.



 Comments   
Comment by Vivian Ge (Inactive) [ 06/Oct/21 ]

Updating the fixversion since branching activities occurred yesterday. This ticket will be in rc0 when it’s been triggered. For more active release information, please keep an eye on #server-release. Thank you!

Comment by Githook User [ 22/Jul/21 ]

Author:

{'name': 'Jackson Xie', 'email': 'jackson.xie@mongodb.com', 'username': 'jacksonx9'}

Message: SERVER-57794: Simple8b RLE
Branch: master
https://github.com/mongodb/mongo/commit/4e64829214e092b966c13099c0c9eeb9027a30a7

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