[GitHub] [orc] wgtmac commented on pull request #915: ORC-98: Add support for t-digests to ORC

[GitBox <gi...@apache.org>]

wgtmac commented on pull request #915:
URL: https://github.com/apache/orc/pull/915#issuecomment-927607518


   > In some environments the test has an overflow check that is not as expected. I haven't figured out why, but I believe this overflow detection code is incorrect.
   > https://github.com/apache/orc/blob/6da96bb8ceb64528d082974efed411c4c29f3408/c%2B%2B/src/Statistics.cc#L180-L190
   > 
   > 
   > A counter-example can easily be given
   > Assume `sum=1`, `update(std::numeric_limits<int64_t>::max(), 3);`
   > `value * repetitions + _stats.getSum()` is overflowed, but is still a positive number : 9223372036854775806
   > @dongjoon-hyun @wgtmac What do you think? :)
   
   This piece of code was simply copied from the java side:
   https://github.com/apache/orc/blob/main/java/core/src/java/org/apache/orc/impl/ColumnStatisticsImpl.java#L362-L379
   
   We need make sure value * repetitions does not overflow before checking the sum. : (


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