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  1. Core Server
  2. SERVER-32532

Two-phase dropDatabase may not replicate all collection drops before the database drop.

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • 3.6.0
    • 3.6.3, 3.7.1
    • Replication
    • None
    • Fully Compatible
    • Repl 2018-01-15

    Description

      The first phase of dropDatabase (for replicate sets) in 3.6 is to individually drop each collection (drop in this first phase is a misnomer for rename). When those "drops" are majority confirmed, the primary replicates a dropDatabase oplog entry.

      However the loop uses an iterator over the _collections map and db->dropCollectionEvenIfSystem will perform a rename. This rename erases the entry followed by adding it back under a different name. The expectation of the for-each collection loop is that all collections will be observed. The erase/add of the underlying map breaks that requirement.

      This can result in some collections not being dropped on the primary nor the secondary in the first part of dropping a database. I do believe the second phase of dropping a database that's associated with the dropDatabase oplog entry will be renamed and/or dropped on both the primary and secondary.

      One possible fix is to copy the values from the map to iterate over instead.

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              benety.goh@mongodb.com Benety Goh
              daniel.gottlieb@mongodb.com Daniel Gottlieb
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