@Override
  public String toString() {
    boolean first = true;
    StringBuilder sb = new StringBuilder();
    for (HCatFieldSchema hfs : fieldSchemas) {
      if (!first) {
        sb.append(",");
      } else {
        first = false;
      }
      if (hfs.getName() != null) {
        sb.append(hfs.getName());
        sb.append(":");
      }
      sb.append(hfs.toString());
    }
    return sb.toString();
  }
Note : The position will be re-numbered when one of the preceding columns are removed.
Hence, the client should not cache this value and expect it to be always valid.
@param fieldName
@return the index of field named fieldName in Schema. If field is not
present, returns null.
hcatalog/core/src/main/java/org/apache/hive/hcatalog/data/schema/HCatSchema.java