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  1. Core Server
  2. SERVER-24266

Large discrepancy in SizeStorer after unclean shutdown

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Details

    • Bug
    • Status: Backlog
    • Major - P3
    • Resolution: Unresolved
    • 3.0.12, 3.2.6, 3.3.6
    • None
    • WiredTiger
    • Storage Execution
    • ALL
    • Hide
      1. Start a standalone mongod instance with wiredTiger storage engine.
      2. Insert documents to a collection until the data volume runs out of disk space.
      3. Allocate/free more disk space for the data volume.
      4. Start the mongod instance again.
      5. Check the results of count() and itcount() for the collection. The numbers are different.
      Show
      Start a standalone mongod instance with wiredTiger storage engine. Insert documents to a collection until the data volume runs out of disk space. Allocate/free more disk space for the data volume. Start the mongod instance again. Check the results of count() and itcount() for the collection. The numbers are different.

    Description

      The mongod instance (with WiredTiger storage engine) is down when there is insufficient disk space for the data volume. After adding more space to the dbpath and restart the mongod instance, count() returns incorrect value as below:

      > db.users.count()
      		 
      1527296
      		 
      > db.users.find().itcount()
      		 
      1605004

      SERVER-19472 and DOCS-5682 mentioned that count may off by up to 1000 documents after an unclean shutdown. However, count off to 70k+ documents in my test.

      Have tested 3.0.12, 3.2.6 and 3.3.6, all have the same issue.

      db.collection.validate(true) will reset the value for count() to the correct number.

      Attachments

        Issue Links

          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. SERVER-20063 WiredTiger collection size cache can be inaccurate

          • Major - P3 - Major loss of function.
          • Closed
          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-45718 Index builder can skip index building for a non-empty collections due to incorrect fast count value.

          • Major - P3 - Major loss of function.
          • Closed
          related to

          Task - A task that needs to be done. DOCS-7979 Size and count in collection stats are persisted during checkpoints in WiredTiger

          • Major - P3 - Major loss of function.
          • Closed

          Activity

            People

              backlog-server-execution Backlog - Storage Execution Team
              linda.qin@mongodb.com Linda Qin
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              Dates

                Created:
                Updated: