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  1. WiredTiger
  2. WT-7037

Investigate more compact representation for small history store records

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    Details

    • Type: Improvement
    • Status: Open
    • Priority: Major - P3
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: Backlog
    • Component/s: None
    • Labels:
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      Description

      WT-6681 showed that a small modify record in the history store—corresponding to changing a few bytes of a MongoDB document—requires about 70 bytes to represent the resulting key and value in the history store.

      We should investigate ways to store this information more compactly.  WT uses packed representations for many items, but Alex Gorrod mentioned that the timestamp format may not see much savings here.  If so, we might save space by storing one full timestamp and representing the others as deltas.  

      This is only going to be a problem for customers or use cases that wind up with a lot of small updates in the history store.  So it might make sense to put this off until there is evidence that it is really a problem. But addressing this would require a change to the data format of the history store, so it might be easier make the change sooner, before durable history use is widespread. 

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            Assignee:
            backlog-server-storage-engines Backlog - Storage Engines Team
            Reporter:
            keith.smith Keith Smith
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