/*
    * Copyright 2006-2012 the original author or authors.
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *	  http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.springframework.batch.item.database.support;
  
  import javax.sql.DataSource;
  
  import org.springframework.batch.item.database.PagingQueryProvider;
  import org.springframework.dao.InvalidDataAccessResourceUsageException;
  import org.springframework.jdbc.support.JdbcUtils;
  
  /**
   * Derby implementation of a  {@link PagingQueryProvider} using standard SQL:2003 windowing functions.
   * These features are supported starting with Apache Derby version 10.4.1.3.
   *
   * As the OVER() function does not support the ORDER BY clause a sub query is instead used to order the results
   * before the ROW_NUM restriction is applied
   *
   * @author Thomas Risberg
   * @author David Thexton
   * @author Michael Minella
   * @since 2.0
   */
  public class DerbyPagingQueryProvider extends SqlWindowingPagingQueryProvider {
  
  	private String version;
  
  	@Override
  	public void init(DataSource dataSource) throws Exception {
  		super.init(dataSource);
  		version = JdbcUtils.extractDatabaseMetaData(dataSource, "getDatabaseProductVersion").toString();
  		if ("10.4.1.3".compareTo(version) > 0) {
  			throw new InvalidDataAccessResourceUsageException("Apache Derby version " + version + " is not supported by this class,  Only version 10.4.1.3 or later is supported");
  		}
  	}
  	
  	@Override
  	protected String getOrderedQueryAlias() {
  		return "TMP_ORDERED";
  	}
  
  	@Override
  	protected String getOverClause() {
  		return "";
  	}
  
      @Override
  	protected String getOverSubstituteClauseStart() {
  		return " FROM (SELECT " + getSelectClause();
  	}
  
      @Override
  	protected String getOverSubstituteClauseEnd() {
  		return " ) AS " + getOrderedQueryAlias();
  	}
  
  }