@PUT
  @Path("ddl/database/{db}/table/{table}/column/{column}")
  @Produces(MediaType.APPLICATION_JSON)
  public Response addOneColumn(@PathParam("db") String db,
                 @PathParam("table") String table,
                 @PathParam("column") String column,
                 ColumnDesc desc)
    throws HcatException, NotAuthorizedException, BusyException,
    BadParam, ExecuteException, IOException {
    verifyUser();
    verifyDdlParam(db, ":db");
    verifyDdlParam(table, ":table");
    verifyParam(column, ":column");
    verifyParam(desc.type, "type");
    desc.name = column;

    HcatDelegator d = new HcatDelegator(appConf, execService);
    return d.addOneColumn(getDoAsUser(), db, table, desc);
  }
Create a column in an hcat table.
hcatalog/webhcat/svr/src/main/java/org/apache/hive/hcatalog/templeton/Server.java