| 1 | /* |
| 2 | * Copyright 2006-2008 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package org.springframework.batch.item.database.support; |
| 18 | |
| 19 | /** |
| 20 | * Postgres implementation of a {@link org.springframework.batch.item.database.PagingQueryProvider} using database specific features. |
| 21 | * |
| 22 | * @author Thomas Risberg |
| 23 | * @since 2.0 |
| 24 | */ |
| 25 | public class PostgresPagingQueryProvider extends AbstractSqlPagingQueryProvider { |
| 26 | |
| 27 | @Override |
| 28 | public String generateFirstPageQuery(int pageSize) { |
| 29 | return SqlPagingQueryUtils.generateLimitSqlQuery(this, false, buildLimitClause(pageSize)); |
| 30 | } |
| 31 | |
| 32 | @Override |
| 33 | public String generateRemainingPagesQuery(int pageSize) { |
| 34 | return SqlPagingQueryUtils.generateLimitSqlQuery(this, true, buildLimitClause(pageSize)); |
| 35 | } |
| 36 | |
| 37 | private String buildLimitClause(int pageSize) { |
| 38 | return new StringBuilder().append("LIMIT ").append(pageSize).toString(); |
| 39 | } |
| 40 | |
| 41 | @Override |
| 42 | public String generateJumpToItemQuery(int itemIndex, int pageSize) { |
| 43 | int page = itemIndex / pageSize; |
| 44 | int offset = (page * pageSize) - 1; |
| 45 | offset = offset<0 ? 0 : offset; |
| 46 | String limitClause = new StringBuilder().append("LIMIT 1 OFFSET ").append(offset).toString(); |
| 47 | return SqlPagingQueryUtils.generateLimitJumpToQuery(this, limitClause); |
| 48 | } |
| 49 | |
| 50 | } |