| 1 | /* ============================================================= |
| 2 | * SmallSQL : a free Java DBMS library for the Java(tm) platform |
| 3 | * ============================================================= |
| 4 | * |
| 5 | * (C) Copyright 2004-2006, by Volker Berlin. |
| 6 | * |
| 7 | * Project Info: http://www.smallsql.de/ |
| 8 | * |
| 9 | * This library is free software; you can redistribute it and/or modify it |
| 10 | * under the terms of the GNU Lesser General Public License as published by |
| 11 | * the Free Software Foundation; either version 2.1 of the License, or |
| 12 | * (at your option) any later version. |
| 13 | * |
| 14 | * This library is distributed in the hope that it will be useful, but |
| 15 | * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| 16 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
| 17 | * License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU Lesser General Public |
| 20 | * License along with this library; if not, write to the Free Software |
| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, |
| 22 | * USA. |
| 23 | * |
| 24 | * [Java is a trademark or registered trademark of Sun Microsystems, Inc. |
| 25 | * in the United States and other countries.] |
| 26 | * |
| 27 | * --------------- |
| 28 | * SortedResult.java |
| 29 | * --------------- |
| 30 | * Author: Volker Berlin |
| 31 | * |
| 32 | */ |
| 33 | package smallsql.database; |
| 34 | |
| 35 | |
| 36 | /** |
| 37 | * Is used to implements the ORDER BY clause. |
| 38 | * |
| 39 | * @author Volker Berlin |
| 40 | */ |
| 41 | final class SortedResult extends RowSource { |
| 42 | |
| 43 | final private Expressions orderBy; |
| 44 | final private RowSource rowSource; |
| 45 | private IndexScrollStatus scrollStatus; |
| 46 | private int row; |
| 47 | private boolean useSetRowPosition; |
| 48 | |
| 49 | SortedResult(RowSource rowSource, Expressions orderBy){ |
| 50 | this.rowSource = rowSource; |
| 51 | this.orderBy = orderBy; |
| 52 | } |
| 53 | |
| 54 | |
| 55 | final boolean isScrollable(){ |
| 56 | return true; //TODO can scrollable implement if Index implement it |
| 57 | } |
| 58 | |
| 59 | |
| 60 | final void execute() throws Exception{ |
| 61 | rowSource.execute(); |
| 62 | Index index = new Index(false); |
| 63 | while(rowSource.next()){ |
| 64 | index.addValues( rowSource.getRowPosition(), orderBy); |
| 65 | } |
| 66 | scrollStatus = index.createScrollStatus(orderBy); |
| 67 | useSetRowPosition = false; |
| 68 | } |
| 69 | |
| 70 | |
| 71 | void beforeFirst() throws Exception { |
| 72 | scrollStatus.reset(); |
| 73 | row = 0; |
| 74 | useSetRowPosition = false; |
| 75 | } |
| 76 | |
| 77 | |
| 78 | boolean first() throws Exception { |
| 79 | beforeFirst(); |
| 80 | return next(); |
| 81 | } |
| 82 | |
| 83 | |
| 84 | boolean previous() throws Exception{ |
| 85 | return nextPrevious( -1 ); |
| 86 | } |
| 87 | |
| 88 | |
| 89 | boolean next() throws Exception { |
| 90 | return nextPrevious( +1 ); |
| 91 | } |
| 92 | |
| 93 | |
| 94 | final private boolean nextPrevious(int scroll) throws Exception{ |
| 95 | if(useSetRowPosition) throw Utils.createSQLException("Internal Error with ORDER BY"); |
| 96 | long rowPosition = scrollStatus.getRowOffset(scroll == 1); |
| 97 | if(rowPosition >= 0){ |
| 98 | rowSource.setRowPosition( rowPosition ); |
| 99 | row += scroll; |
| 100 | return true; |
| 101 | }else{ |
| 102 | noRow(); |
| 103 | return false; |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | |
| 108 | boolean last() throws Exception{ |
| 109 | afterLast(); |
| 110 | return previous(); |
| 111 | } |
| 112 | |
| 113 | |
| 114 | void afterLast(){ |
| 115 | scrollStatus.afterLast(); |
| 116 | noRow(); |
| 117 | useSetRowPosition = false; |
| 118 | } |
| 119 | |
| 120 | |
| 121 | int getRow(){ |
| 122 | return row; |
| 123 | } |
| 124 | |
| 125 | |
| 126 | final long getRowPosition(){ |
| 127 | return rowSource.getRowPosition(); |
| 128 | } |
| 129 | |
| 130 | |
| 131 | final void setRowPosition(long rowPosition) throws Exception{ |
| 132 | rowSource.setRowPosition(rowPosition); |
| 133 | useSetRowPosition = true; |
| 134 | } |
| 135 | |
| 136 | |
| 137 | final boolean rowInserted(){ |
| 138 | return rowSource.rowInserted(); |
| 139 | } |
| 140 | |
| 141 | |
| 142 | final boolean rowDeleted(){ |
| 143 | return rowSource.rowDeleted(); |
| 144 | } |
| 145 | |
| 146 | |
| 147 | void nullRow() { |
| 148 | rowSource.nullRow(); |
| 149 | row = 0; |
| 150 | |
| 151 | } |
| 152 | |
| 153 | |
| 154 | void noRow() { |
| 155 | rowSource.noRow(); |
| 156 | row = 0; |
| 157 | } |
| 158 | |
| 159 | } |