JdbcPagingItemReader - Not able to provide table alias in the column name in the sortKeys [BATCH-2854]

Shakti Tripathy opened BATCH-2854 and commented

If a table alias is given along with the column name for a sort key e.g. 

JdbcPagingItemReader reader = new JdbcPagingItemReader();

PostgresPagingQueryProvider provider = new PostgresPagingQueryProvider();

....

Map<String, Order> sortKeys = new HashMap<>();

sortKeys.put("mu.student_id", Order.ASCENDING);

provider.setSortKeys(sortKeys);

The code fails in JdbcPagingItemReader.PagingRowMapper 

private class PagingRowMapper implements RowMapper<T> {
   @Override
   public T mapRow(ResultSet rs, int rowNum) throws SQLException {
      startAfterValues = new LinkedHashMap<>();
      for (Map.Entry<String, Order> sortKey : queryProvider.getSortKeys().entrySet()) {
        startAfterValues.put(sortKey.getKey(), rs.getObject(sortKey.getKey()));
      }

     return rowMapper.mapRow(rs, rowNum);
   }
}

While its trying to get the column from resultset as mu.student_id, it fails. Can we remove any preceding aliases before the DOT(.) before pulling the column from the resultset.

The aliases are needed when using a join query.

Affects: 4.2.0

Start with JdbcPagingItemReader.PagingRowMapper and the sort-key handling used by PostgresPagingQueryProvider. Trace how each sort-key name is passed to ResultSet, then verify that a qualified key such as mu.student_id still supports joined queries while retrieving the unqualified result-set column.