/*
    * 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 org.springframework.batch.item.database.PagingQueryProvider;
  import org.springframework.util.StringUtils;
  
  /**
   * DB2 implementation of a {@link PagingQueryProvider} using
   * database specific features.
   *
   * @author Thomas Risberg
   * @author Michael Minella
   * @since 2.0
   */
  public class Db2PagingQueryProvider extends SqlWindowingPagingQueryProvider {
  
  	@Override
  	public String generateFirstPageQuery(int pageSize) {
  		return SqlPagingQueryUtils.generateLimitSqlQuery(this, false, buildLimitClause(pageSize));
  	}
  
  	@Override
  	public String generateRemainingPagesQuery(int pageSize) {
  		if(StringUtils.hasText(getGroupClause())) {
  			return SqlPagingQueryUtils.generateLimitGroupedSqlQuery(this, true, buildLimitClause(pageSize));
  		}
  		else {
  			return SqlPagingQueryUtils.generateLimitSqlQuery(this, true, buildLimitClause(pageSize));
  		}
  	}
  
  	@Override
  	protected Object getSubQueryAlias() {
  		return "AS TMP_SUB ";
  	}
  
  	private String buildLimitClause(int pageSize) {
  		return new StringBuilder().append("FETCH FIRST ").append(pageSize).append(" ROWS ONLY").toString();
  	}
  
  }