public static boolean qualifierStartsWith(final Cell left, final byte[] startsWith) {
    if (startsWith == null || startsWith.length == 0) {
      throw new IllegalArgumentException("Cannot pass an empty startsWith");
    }
    if (left.getQualifierLength() < startsWith.length) {
      return false;
    }
    if (left instanceof ByteBufferExtendedCell) {
      return ByteBufferUtils.equals(((ByteBufferExtendedCell) left).getQualifierByteBuffer(),
        ((ByteBufferExtendedCell) left).getQualifierPosition(), startsWith.length, startsWith, 0,
        startsWith.length);
    }
    return Bytes.equals(left.getQualifierArray(), left.getQualifierOffset(), startsWith.length,
      startsWith, 0, startsWith.length);
  }
Finds if the start of the qualifier part of the Cell matches <code>buf</code>
@param left       the cell with which we need to match the qualifier
@param startsWith the serialized keyvalue format byte[]
@return true if the qualifier have same staring characters, false otherwise
hbase-common/src/main/java/org/apache/hadoop/hbase/PrivateCellUtil.java