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  1. Core Server
  2. SERVER-27127

drop() regression heisenbug

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    • Icon: Bug Bug
    • Resolution: Done
    • Icon: Major - P3 Major - P3
    • None
    • 3.4.0-rc1, 3.4.0-rc3, 3.4.0-rc4
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      Install libmongoc 1.5.0-rc6, checkout the branch from the github link above, build the mongocxx driver and run tests repeatedly.

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      Install libmongoc 1.5.0-rc6, checkout the branch from the github link above, build the mongocxx driver and run tests repeatedly.
    • Storage 2016-12-12

    Description

      In developing mongocxx, I stumbled across a bug where a collection drop followed immediately by a count on the collection with an empty document filter doesn't always return a count of zero. This occurs in fixture code, so the collection is being repeatedly filled and dropped for different tests.

      The problem was seen on some (but only some) test runs on 3.4-rc1, 3.4-rc3 and 3.4-rc4. (3.4-rc2 was not tested). The problem did not occur on 3.2.9 or 3.2.11.

      Replacing the drop with multi-document delete does not exhibit the problem on any of the 3.4 rc's.

      I don't have time to do a more complete investigation, but I wanted to file a ticket so that it wasn't lost and others could explore it.

      The failing test code can be seen here: https://github.com/xdg/mongo-cxx-driver/blob/CXX-894-server-bug-demo/src/mongocxx/test/collection.cpp#L98-L103

      Tests were run on my macbook.

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        1. server21727.js
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        2. server27127.cpp
          2 kB
        3. server27127.log
          6 kB

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            milkie@mongodb.com Eric Milkie
            david.golden@mongodb.com David Golden
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              Updated:
              Resolved: