DRILL-6629 BitVector split and transfer does not work correctly for transfer length < 8

closes #1395

1 files changed, 7 insertions, 1 deletions

diff --git a/exec/vector/src/main/java/org/apache/drill/exec/vector/BitVector.java b/exec/vector/src/main/java/org/apache/drill/exec/vector/BitVector.java
index 0dd34f51e..a6b87378d 100644
--- a/exec/vector/src/main/java/org/apache/drill/exec/vector/BitVector.java
+++ b/exec/vector/src/main/java/org/apache/drill/exec/vector/BitVector.java
@@ -323,8 +323,14 @@ public final class BitVector extends BaseDataValueVector implements FixedWidthVe
       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;
         byte bitsFromLastButOneByte = (byte)((lastButOneByte & 0xFF) >>> firstBitOffset);
+        // if last bit to be copied is before the end of the first byte, then mask of the trailing extra bits
+        if (8 > (length + firstBitOffset)) {
+          byte mask = (byte)((0x1 << length) - 1);
+          bitsFromLastButOneByte = (byte)((bitsFromLastButOneByte & mask));
+        }
 
         // If we have to read more bits than what we have already read, read it into lastByte otherwise set lastByte to 0.
         // (length % 8) is num of remaining bits to be read.