[GitHub] ppadma commented on a change in pull request #1395: DRILL-6629 BitVector split and transfer does not work correctly for transfer length < 8

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ppadma commented on a change in pull request #1395: DRILL-6629 BitVector split and transfer does not work correctly for transfer length < 8
URL: https://github.com/apache/drill/pull/1395#discussion_r204918913
 
 

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 File path: exec/vector/src/main/java/org/apache/drill/exec/vector/BitVector.java
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 @@ -323,7 +323,8 @@ public void splitAndTransferTo(int startIndex, int length, BitVector target) {
       if (length % 8 != 0) {
         // start is not byte aligned so we have to copy some bits from the last full byte read in the
         // previous loop
-        byte lastButOneByte = byteIPlus1;
+        // if numBytesHoldingSourceBits == 1, lastButOneByte is the first byte, but we have not read it yet, so read it
+        byte lastButOneByte = (numBytesHoldingSourceBits == 1) ? this.data.getByte(firstByteIndex) : byteIPlus1;
 
 Review comment:
   @bitblender I think there could be a problem here. please check. If you are copying say from firstBitOffset 2, length 4. We want to copy 4  bits only. But, this might copy 6 bits. bitsFromLastButOneByte will be all bits from firstBitOffset to the end of the byte. 

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