[jira] [Created] (HIVE-20664) Potential ArrayIndexOutOfBoundsException in VectorizedOrcAcidRowBatchReader.findMinMaxKeys

["Saurabh Seth (JIRA)" <ji...@apache.org>]

Saurabh Seth created HIVE-20664:
-----------------------------------

             Summary: Potential ArrayIndexOutOfBoundsException in VectorizedOrcAcidRowBatchReader.findMinMaxKeys
                 Key: HIVE-20664
                 URL: https://issues.apache.org/jira/browse/HIVE-20664
             Project: Hive
          Issue Type: Bug
          Components: Transactions
            Reporter: Saurabh Seth
            Assignee: Saurabh Seth


[~ekoifman], could you please confirm if my understanding is correct and if so, review the fix?

In the method {{VectorizedOrcAcidRowBatchReader.findMinMaxKeys}}, the code snippet that identifies the first and last stripe indices in the current split could result in an ArrayIndexOutOfBoundsException if a complete split is within the same stripe:
{noformat}
    for(int i = 0; i < stripes.size(); i++) {
      StripeInformation stripe = stripes.get(i);
      long stripeEnd = stripe.getOffset() + stripe.getLength();
      if(firstStripeIndex == -1 && stripe.getOffset() >= splitStart) {
        firstStripeIndex = i;
      }
      if(lastStripeIndex == -1 && splitEnd <= stripeEnd &&
          stripes.get(firstStripeIndex).getOffset() <= stripe.getOffset() ) {
        //the last condition is for when both splitStart and splitEnd are in
        // the same stripe
        lastStripeIndex = i;
      }
    }
{noformat}
Consider the example where there are 2 stripes - 0-500 and 500-1000 and splitStart is 600 and splitEnd is 800.

In the first iteration of the loop, stripe.getOffset() is 0 and stripeEnd is 500. In this iteration, neither of the if statement conditions will be met and firstSripeIndex as well as lastStripeIndex remain -1.

In the second iteration of the loop stripe.getOffset() is 500, stripeEnd is 1000, The first if statement condition will not be met in this case because stripe's offset (500) is not greater than or equal to the splitStart (600). However, in the second if statement, splitEnd (800) is <= stripeEnd(1000) and it will try to compute the last condition {{stripes.get(firstStripeIndex).getOffset() <= stripe.getOffset()}}. This will throw an ArrayIndexOutOfBoundsException because firstStripeIndex is still -1.

I'm not sure if this scenario is possible at all, hence logging this as a low priority issue. Perhaps block based split generation using BISplitStrategy could trigger this?



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