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34 package smallsql.database;
35
36
37
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 }
138 |
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