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  1. Documentation
  2. DOCS-13775

Investigate changes in SERVER-47824: Ban transaction snapshot reads on capped collections

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Details

    • Task
    • Status: Closed
    • Major - P3
    • Resolution: Done
    • None
    • 4.7.0
    • manual, Server
    • None
    • 2
    • ServerDocs2020: Feb2 - Feb9, ServerDocs2020: Feb9 - Feb16
    • true

    Description

      Description

      Downstream Change Summary

      Transaction snapshot reads are now banned on capped collections.

      Description of Linked Ticket

      Capped collections typically (always?) delete records with an unreplicated/untimestamped write. Those deletions will always become visible in a newer transaction. So if a transaction uses snapshot with an atClusterTime (e.g. coming from mongos), it may not see some deleted documents even if they existed at the point in time requested.

      Snapshot transactions without atClusterTime might still work if the snapshot is open before the deletions happen probably because they hold onto the WT txn and the snapshot. But I am not 100% sure. Either way, it seems that we will still have to ban transaction snapshot reads on capped collections unless we choose to timestamp the capped collection deletions.

      Scope of changes

      Pages to review and update:

      Impact to Other Docs

      MVP (Work and Date)

      Resources (Scope or Design Docs, Invision, etc.)

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              naomi.pentrel@mongodb.com Naomi Pentrel (Inactive)
              backlog-server-pm Backlog - Core Eng Program Management Team
              Naomi Pentrel Naomi Pentrel (Inactive)
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              Dates

                Created:
                Updated:
                Resolved:
                1 year, 25 weeks, 6 days ago