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  1. WiredTiger
  2. WT-3669

Check for aborted updates during reconciliation

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 3.6.0-rc2, WT3.0.0
    • Component/s: None
    • Labels:
      None
    • Sprint:
      Storage 2017-10-23

      Description

      During WT-3435, the way we check for uncommitted updates during reconciliation changed.

      That check was updated in WT-3406 to fix a bug that caused updates to be written into page images, if the transaction that wrote the update rolled back concurrent with reconciliation of a page.

      Here is the original description:

      Reconciliation reads upd->txnid into a local variable, then the transaction rolls back (say), setting upd->txnid = WT_TXN_ABORTED. Then txn_global->last_running is updated so the cached txnid is older than the oldest running transaction, causing __wt_txn_committed to return true.

      At this point, reconciliation thinks it has a committed update (based on the cached txnid) but the actual transaction has rolled back.

      I believe we have reintroduced this bug by not checking uncommitted and instead relying on __wt_txn_visible_all, which has the same race as in WT-3406 (by the time we determine that a cached copy of some transaction ID is more recent than the oldest, it can have rolled back in the WT_UPDATE).

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            Assignee:
            michael.cahill Michael Cahill
            Reporter:
            michael.cahill Michael Cahill
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              Dates

              Created:
              Updated:
              Resolved: