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https://issues.apache.org/jira/browse/DRILL-6629?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16558725#comment-16558725
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ASF GitHub Bot commented on DRILL-6629:
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bitblender 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_r205559272
##########
File path:
exec/vector/src/main/java/org/apache/drill/exec/vector/BitVector.java
##########
@@ -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:
Yes. This can happen. Good observation!
I did not handle it in the initial PR because this can happen only in the
single-byte (length < 8) case, so there is always allocated memory available(at
least 1 byte is alloced in the target vector) to write the extra bits and since
valueCount of the target was being set correctly, this was not a concern.
Writing the extra bits would have no observable impact if the buffer was not
zero-initialized.
But since we are zero-initializing buffers, it makes sense to be precise and
leave bits beyond valueCount as 0. I have made changes to mask off the extra
bits.
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> BitVector split and transfer does not work correctly for transfer length < 8
> ----------------------------------------------------------------------------
>
> Key: DRILL-6629
> URL: https://issues.apache.org/jira/browse/DRILL-6629
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Data Types
> Environment: BitVector split and transfer does not work correctly for
> transfer length < 8.
> Reporter: Karthikeyan Manivannan
> Assignee: Karthikeyan Manivannan
> Priority: Major
> Fix For: 1.15.0
>
>
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