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  1. IMPALA
  2. IMPALA-5560

Consider always storing CHAR() slots inline

    Details

    • Type: Improvement
    • Status: Resolved
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: Impala 2.10.0
    • Fix Version/s: Impala 2.10.0
    • Component/s: Backend, Frontend
    • Labels:
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      Description

      Currently we have two distinct representations for CHAR slots: one that stores the CHAR(N) inline in the tuple when N <= 128 and another that stores it out-of-line from the tuple when 128 < N <= 255.

      We could simplify the code and improve our test coverage by only using a single representation. I think that test coverage for the out-of-line storage has some large gaps so I don't have a high degree of confidence that it is correct in all cases.

      The main benefit to the out-of-line storage seems to be that it consumes less space for NULL values. It could also improve cache locality in some cases. These benefits seem marginal though, particularly since CHAR(129+) is probably used only infrequently.

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              • Assignee:
                tarmstrong Tim Armstrong
                Reporter:
                tarmstrong Tim Armstrong
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                • Created:
                  Updated:
                  Resolved: