public String makeFilenameWithCopyIndex(int idx) throws HiveException {
    if (filePrefixForCopy == null) {
      throw new HiveException("Not expected format for copying files.");
    }
    return filePrefixForCopy + "_copy_" + idx;
  }
Create a copy file using the same file name as this and the given index. It will keep the prefixes but drop any
suffixes.
Ex: 00001_02 will be converted to 00001_02_copy_3 for idx = 3.
tmp_(prefix)00001_02_copy_1.snappy.orc will be converted to tmp_(prefix)00001_02_copy_3 for idx = 3
@param idx The index required.
@return
ql/src/java/org/apache/hadoop/hive/ql/exec/ParsedOutputFileName.java