| 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 | * Where.java |
| 29 | * --------------- |
| 30 | * Author: Volker Berlin |
| 31 | * |
| 32 | * Created on 31.07.2004 |
| 33 | */ |
| 34 | package smallsql.database; |
| 35 | |
| 36 | |
| 37 | /** |
| 38 | * @author Volker Berlin |
| 39 | */ |
| 40 | final class Distinct extends RowSource { |
| 41 | |
| 42 | final private Expressions columns; |
| 43 | final private RowSource rowSource; |
| 44 | private Index index; |
| 45 | private int row; |
| 46 | |
| 47 | Distinct(RowSource rowSource, Expressions columns){ |
| 48 | this.rowSource = rowSource; |
| 49 | this.columns = columns; |
| 50 | } |
| 51 | |
| 52 | |
| 53 | final void execute() throws Exception{ |
| 54 | rowSource.execute(); |
| 55 | index = new Index(true); |
| 56 | } |
| 57 | |
| 58 | |
| 59 | final boolean isScrollable() { |
| 60 | return false; |
| 61 | } |
| 62 | |
| 63 | |
| 64 | final void beforeFirst() throws Exception { |
| 65 | rowSource.beforeFirst(); |
| 66 | row = 0; |
| 67 | } |
| 68 | |
| 69 | |
| 70 | final boolean first() throws Exception { |
| 71 | beforeFirst(); |
| 72 | return next(); |
| 73 | } |
| 74 | |
| 75 | |
| 76 | final boolean next() throws Exception { |
| 77 | while(true){ |
| 78 | boolean isNext = rowSource.next(); |
| 79 | if(!isNext) return false; |
| 80 | |
| 81 | Long oldRowOffset = (Long)index.findRows(columns, null); |
| 82 | long newRowOffset = rowSource.getRowPosition(); |
| 83 | if(oldRowOffset == null){ |
| 84 | index.addValues( newRowOffset, columns); |
| 85 | row++; |
| 86 | return true; |
| 87 | }else |
| 88 | if(oldRowOffset.longValue() == newRowOffset){ |
| 89 | row++; |
| 90 | return true; |
| 91 | } |
| 92 | } |
| 93 | } |
| 94 | |
| 95 | |
| 96 | final void afterLast() throws Exception { |
| 97 | rowSource.afterLast(); |
| 98 | row = 0; |
| 99 | } |
| 100 | |
| 101 | |
| 102 | final int getRow() throws Exception { |
| 103 | return row; |
| 104 | } |
| 105 | |
| 106 | |
| 107 | final long getRowPosition() { |
| 108 | return rowSource.getRowPosition(); |
| 109 | } |
| 110 | |
| 111 | |
| 112 | final void setRowPosition(long rowPosition) throws Exception { |
| 113 | rowSource.setRowPosition(rowPosition); |
| 114 | } |
| 115 | |
| 116 | |
| 117 | final void nullRow() { |
| 118 | rowSource.nullRow(); |
| 119 | row = 0; |
| 120 | } |
| 121 | |
| 122 | |
| 123 | final void noRow() { |
| 124 | rowSource.noRow(); |
| 125 | row = 0; |
| 126 | } |
| 127 | |
| 128 | |
| 129 | final boolean rowInserted(){ |
| 130 | return rowSource.rowInserted(); |
| 131 | } |
| 132 | |
| 133 | |
| 134 | final boolean rowDeleted() { |
| 135 | return rowSource.rowDeleted(); |
| 136 | } |
| 137 | } |