mydumper -r can not handle negative index

[Thomas Wen]

when i use mydumper -r to dump a blog database (this blog use a negative primary key). mydumer master thread hung. and dump thread can not get job to do.
i found the codes in get_chunks_for_table below is the reason:

 /* This is estimate, not to use as guarantee! Every chunk would have eventual adjustments */
 guint64 estimated_chunks = rows / rows_per_file;
 guint64 estimated_step, nmin, nmax, cutoff;

 /* Support just bigger INTs for now, very dumb, no verify approach */
 switch (fields[0].type) {
  case MYSQL_TYPE_LONG:
  case MYSQL_TYPE_LONGLONG:
  case MYSQL_TYPE_INT24:
   /* static stepping */
   nmin = strtoll(min,NULL,10);
   nmax = strtoll(max,NULL,10);
   estimated_step = (nmax-nmin)/estimated_chunks+1;
   cutoff = nmin;
   while(cutoff<=nmax) {
    chunks=g_list_append(chunks,g_strdup_printf("%s%s%s%s(`%s` >= %llu AND `%s` < %llu)",
      !showed_nulls?"`":"",
      !showed_nulls?field:"",
      !showed_nulls?"`":"",
      !showed_nulls?" IS NULL OR ":"",
      field, (unsigned long long)cutoff,
      field, (unsigned long long)(cutoff+estimated_step)));
    cutoff+=estimated_step;
    showed_nulls=1;
   }

  default:
   goto cleanup;
 }

nmin and nmax should be gint64, not guint64
may the codes below is correct:

 /* This is estimate, not to use as guarantee! Every chunk would have eventual adjustments */
 gint64 estimated_chunks = rows / rows_per_file;
 gint64 estimated_step, nmin, nmax, cutoff;

 /* Support just bigger INTs for now, very dumb, no verify approach */
 switch (fields[0].type) {
  case MYSQL_TYPE_LONG:
  case MYSQL_TYPE_LONGLONG:
  case MYSQL_TYPE_INT24:
   /* static stepping */
   nmin = strtoll(min,NULL,10);
   nmax = strtoll(max,NULL,10);
   estimated_step = (nmax-nmin)/estimated_chunks+1;
   cutoff = nmin;
   while(cutoff<=nmax) {
    chunks=g_list_append(chunks,g_strdup_printf("%s%s%s%s(`%s` >= %lld AND `%s` < %lld)",
      !showed_nulls?"`":"",
      !showed_nulls?field:"",
      !showed_nulls?"`":"",
      !showed_nulls?" IS NULL OR ":"",
      field, (long long)cutoff,
      field, (long long)(cutoff+estimated_step)));
    cutoff+=estimated_step;
    showed_nulls=1;
   }

  default:
   goto cleanup;
 }