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  1. WiredTiger
  2. WT-6462

Use read uncommitted isolation level for history store operations

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    Details

    • Type: Task
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: WT3.2.2, 4.4.0-rc12, 4.7.0
    • Component/s: None
    • Labels:
      None
    • Story Points:
      8
    • Sprint:
      Storage - Ra 2020-06-29, Storage - Ra 2020-07-13

      Description

      While investigating WT-6412, Alexander Gorrod pointed out that in some cases traversals of the history store never see any content. We suspect that there is a gap in our actual implementation of history store visibility checks and how we expected them to work. The check in __txn_visible_id isn't what is expected for operations on the history store and due to this check we often won't see any value unless it's globally visible.

      We get away with it because we short-circuit the visibility check in __txn_visible_id in many cases for the history store via a check in __wt_txn_upd_visible_type

      The aim of this ticket is to understand what needs to be done to bring history store visibility checks closer to expected behaviour.

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              Assignee:
              haseeb.bokhari Haseeb Bokhari
              Reporter:
              haseeb.bokhari Haseeb Bokhari
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                Updated:
                Resolved: