@Override
  public List<SQLNotNullConstraint> getNotNullConstraints(String catName, String db_name, String tbl_name)
      throws MetaException {
    NotNullConstraintsRequest request = new NotNullConstraintsRequest(catName, db_name, tbl_name);
    return getNotNullConstraints(request);
  }
Get partition's column stats

@return Map of column name and its stats
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java