public void setContains() {
      isSingleCount = KeyRef.getIsSingleFlag(refWord);

      if (isSingleCount) {
        count = 1;
      } else {
        count =
            multiSetStore.writeBuffers.readInt(
                absoluteOffset - MultiSetCount.byteLength, readPos);
      }
      setJoinResult(JoinResult.MATCH);
    }
Mark the key matched with equalKey as a match and read the set membership count,
if necessary.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/fast/VectorMapJoinFastBytesHashMultiSetStore.java