| 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 | import org.springframework.util.StringUtils; |
| 20 | |
| 21 | /** |
| 22 | * Generic Paging Query Provider using standard SQL:2003 windowing functions. |
| 23 | * These features are supported by DB2, Oracle, SQL Server 2005, Sybase and |
| 24 | * Apache Derby version 10.4.1.3 |
| 25 | * |
| 26 | * @author Thomas Risberg |
| 27 | * @since 2.0 |
| 28 | */ |
| 29 | public class SqlWindowingPagingQueryProvider extends AbstractSqlPagingQueryProvider { |
| 30 | |
| 31 | @Override |
| 32 | public String generateFirstPageQuery(int pageSize) { |
| 33 | StringBuilder sql = new StringBuilder(); |
| 34 | sql.append("SELECT * FROM ( "); |
| 35 | sql.append("SELECT ").append(getSelectClause()).append(", "); |
| 36 | sql.append("ROW_NUMBER() OVER (").append(getOverClause()); |
| 37 | sql.append(") AS ROW_NUMBER"); |
| 38 | sql.append(getOverSubstituteClauseStart()); |
| 39 | sql.append(" FROM ").append(getFromClause()).append( |
| 40 | getWhereClause() == null ? "" : " WHERE " + getWhereClause()); |
| 41 | sql.append(getOverSubstituteClauseEnd()); |
| 42 | sql.append(") ").append(getSubQueryAlias()).append("WHERE ").append(extractTableAlias()).append( |
| 43 | "ROW_NUMBER <= ").append(pageSize); |
| 44 | |
| 45 | return sql.toString(); |
| 46 | } |
| 47 | |
| 48 | protected Object getSubQueryAlias() { |
| 49 | return "AS TMP_SUB "; |
| 50 | } |
| 51 | |
| 52 | protected Object extractTableAlias() { |
| 53 | String alias = "" + getSubQueryAlias(); |
| 54 | if (StringUtils.hasText(alias) && alias.toUpperCase().startsWith("AS")) { |
| 55 | alias = alias.substring(3).trim() + "."; |
| 56 | } |
| 57 | return alias; |
| 58 | } |
| 59 | |
| 60 | @Override |
| 61 | public String generateRemainingPagesQuery(int pageSize) { |
| 62 | StringBuilder sql = new StringBuilder(); |
| 63 | sql.append("SELECT * FROM ( "); |
| 64 | sql.append("SELECT ").append(getSelectClause()).append(", "); |
| 65 | sql.append("ROW_NUMBER() OVER (").append(getOverClause()); |
| 66 | sql.append(") AS ROW_NUMBER"); |
| 67 | sql.append(getOverSubstituteClauseStart()); |
| 68 | sql.append(" FROM ").append(getFromClause()); |
| 69 | sql.append(" WHERE "); |
| 70 | if (getWhereClause() != null) { |
| 71 | sql.append(getWhereClause()); |
| 72 | sql.append(" AND "); |
| 73 | } |
| 74 | sql.append(getSortKey()); |
| 75 | if (isAscending()) { |
| 76 | sql.append(" > "); |
| 77 | } |
| 78 | else { |
| 79 | sql.append(" < "); |
| 80 | } |
| 81 | sql.append(getSortKeyPlaceHolder()); |
| 82 | sql.append(getOverSubstituteClauseEnd()); |
| 83 | sql.append(") ").append(getSubQueryAlias()).append("WHERE ").append(extractTableAlias()).append( |
| 84 | "ROW_NUMBER <= ").append(pageSize); |
| 85 | |
| 86 | return sql.toString(); |
| 87 | } |
| 88 | |
| 89 | @Override |
| 90 | public String generateJumpToItemQuery(int itemIndex, int pageSize) { |
| 91 | int page = itemIndex / pageSize; |
| 92 | int lastRowNum = (page * pageSize); |
| 93 | if (lastRowNum <= 0) { |
| 94 | lastRowNum = 1; |
| 95 | } |
| 96 | |
| 97 | StringBuilder sql = new StringBuilder(); |
| 98 | sql.append("SELECT SORT_KEY FROM ( "); |
| 99 | sql.append("SELECT ").append(getSortKey()).append(" AS SORT_KEY, "); |
| 100 | sql.append("ROW_NUMBER() OVER (").append(getOverClause()); |
| 101 | sql.append(") AS ROW_NUMBER"); |
| 102 | sql.append(getOverSubstituteClauseStart()); |
| 103 | sql.append(" FROM ").append(getFromClause()); |
| 104 | sql.append(getWhereClause() == null ? "" : " WHERE " + getWhereClause()); |
| 105 | sql.append(getOverSubstituteClauseEnd()); |
| 106 | sql.append(") ").append(getSubQueryAlias()).append("WHERE ").append(extractTableAlias()).append( |
| 107 | "ROW_NUMBER = ").append(lastRowNum); |
| 108 | |
| 109 | return sql.toString(); |
| 110 | } |
| 111 | |
| 112 | protected String getOverClause() { |
| 113 | return "ORDER BY " + getSortKeyWithoutAlias() + " " + getAscendingClause(); |
| 114 | } |
| 115 | |
| 116 | protected String getOverSubstituteClauseStart() { |
| 117 | return ""; |
| 118 | } |
| 119 | |
| 120 | protected String getOverSubstituteClauseEnd() { |
| 121 | return ""; |
| 122 | } |
| 123 | |
| 124 | private String getAscendingClause() { |
| 125 | if (isAscending()) { |
| 126 | return "ASC"; |
| 127 | } |
| 128 | else { |
| 129 | return "DESC"; |
| 130 | } |
| 131 | } |
| 132 | |
| 133 | } |