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  1. WiredTiger
  2. WT-4956

Handle the case where 4 billion updates are made to a page without eviction

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Details

    • Task
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • 4.2.1, WT3.2.1, 4.3.1, 4.0.13, 3.6.15, 3.4.24
    • None
    • None
    • 3
    • Storage Engines 2019-07-29, Storage Engines 2019-08-12
    • v4.2, v4.0, v3.6, v3.4

    Description

      We have code that maintains a write generation on each page. Every time an update is added to a page the write generation is incremented. When the page is marked clean by reconciliation the write generation is reset to 0.

      It is possible to construct a workload where checkpoints don't mark the page clean (there is always an update in front of the checkpoint), and the page is never evicted from cache either (never split). A case where this might be the case is a single document is being updated very regularly.

      We should fix the write generation code to be resilient to the write generation wrapping, or implement a clean/dirty tracking mechanism that isn't susceptible to wrapping.

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            alex.cameron@mongodb.com Alex Cameron (Inactive)
            alexander.gorrod@mongodb.com Alexander Gorrod
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            Dates

              Created:
              Updated:
              Resolved: