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  1. HBase
  2. HBASE-7342

Split operation without split key incorrectly finds the middle key in off-by-one error

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Details

    • Bug
    • Status: Closed
    • Minor
    • Resolution: Fixed
    • 0.94.1, 0.94.2, 0.94.3, 0.95.2
    • 0.94.4, 0.95.0
    • HFile, io
    • None
    • Reviewed

    Description

      I took a deeper look into issues I was having using region splitting when specifying a region (but not a key for splitting).

      The midkey calculation is off by one and when there are 2 rows, will pick the 0th one. This causes the firstkey to be the same as midkey and the split will fail. Removing the -1 causes it work correctly, as per the test I've added.

      Looking into the code here is what goes on:

      1. Split takes the largest storefile
      2. It puts all the keys into a 2-dimensional array called blockKeys[][]. Key i resides as blockKeys[i]
      3. Getting the middle root-level index should yield the key in the middle of the storefile
      4. In step 3, we see that there is a possible erroneous (-1) to adjust for the 0-offset indexing.
      5. In a result with where there are only 2 blockKeys, this yields the 0th block key.
      6. Unfortunately, this is the same block key that 'firstKey' will be.
      7. This yields the result in HStore.java:1873 ("cannot split because midkey is the same as first or last row")
      8. Removing the -1 solves the problem (in this case).

      Attachments

        1. 7342-0.94.txt
          3 kB
          Ted Yu
        2. 7342-trunk-v3.txt
          4 kB
          Ted Yu
        3. HBASE-7342-v1.patch
          4 kB
          Aleksandr Shulman
        4. HBASE-7342-v2.patch
          4 kB
          Aleksandr Shulman

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            aleksshulman Aleksandr Shulman
            aleksshulman Aleksandr Shulman
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              Created:
              Updated:
              Resolved: