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1
5 package org.h2.result;
6
7 import java.sql.SQLException  ;
8
9 import org.h2.engine.Constants;
10 import org.h2.engine.Database;
11 import org.h2.engine.Session;
12 import org.h2.store.DataPage;
13 import org.h2.store.FileStore;
14 import org.h2.util.ObjectArray;
15 import org.h2.value.Value;
16
17 class ResultDiskBuffer {
18
19 private static final int READ_AHEAD = 128;
20
21 private DataPage rowBuff;
22 private FileStore file;
23 private ObjectArray tapes;
24 private ResultDiskTape mainTape;
25 private SortOrder sort;
26 private int columnCount;
27
28 public ResultDiskBuffer(Session session, SortOrder sort, int columnCount) throws SQLException {
29 this.sort = sort;
30 this.columnCount = columnCount;
31 Database db = session.getDatabase();
32 rowBuff = DataPage.create(db, Constants.DEFAULT_DATA_PAGE_SIZE);
33 String fileName = session.getDatabase().createTempFile();
34 file = session.getDatabase().openFile(fileName, false);
35 file.autoDelete();
36 file.seek(FileStore.HEADER_LENGTH);
37 if (sort != null) {
38 tapes = new ObjectArray();
39 } else {
40 mainTape = new ResultDiskTape();
41 mainTape.pos = FileStore.HEADER_LENGTH;
42 }
43 }
44
45 public void addRows(ObjectArray rows) throws SQLException {
46 if (sort != null) {
47 sort.sort(rows);
48 }
49 DataPage buff = rowBuff;
50 long start = file.getFilePointer();
51 for (int i = 0; i < rows.size(); i++) {
52 buff.reset();
53 buff.writeInt(0);
54 Value[] row = (Value[]) rows.get(i);
55 for (int j = 0; j < columnCount; j++) {
56 buff.writeValue(row[j]);
57 }
58 buff.fillAligned();
59 int len = buff.length();
60 buff.setInt(0, len);
61 buff.updateChecksum();
62 file.write(buff.getBytes(), 0, len);
63 }
64 if (sort != null) {
65 ResultDiskTape tape = new ResultDiskTape();
66 tape.start = start;
67 tape.end = file.getFilePointer();
68 tapes.add(tape);
69 } else {
70 mainTape.end = file.getFilePointer();
71 }
72 }
73
74 public void done() throws SQLException {
75 file.seek(FileStore.HEADER_LENGTH);
76 }
77
78 public void reset() {
79 if (sort != null) {
80 for (int i = 0; i < tapes.size(); i++) {
81 ResultDiskTape tape = getTape(i);
82 tape.pos = tape.start;
83 tape.buffer = new ObjectArray();
84 }
85 } else {
86 mainTape.pos = FileStore.HEADER_LENGTH;
87 }
88 }
89
90 private void readRow(ResultDiskTape tape) throws SQLException {
91 int min = Constants.FILE_BLOCK_SIZE;
92 DataPage buff = rowBuff;
93 buff.reset();
94 file.readFully(buff.getBytes(), 0, min);
95 int len = buff.readInt();
96 buff.checkCapacity(len);
97 if(len-min > 0) {
98 file.readFully(buff.getBytes(), min, len - min);
99 }
100 buff.check(len);
101 tape.pos += len;
102 Value[] row = new Value[columnCount];
103 for (int k = 0; k < columnCount; k++) {
104 row[k] = buff.readValue();
105 }
106 tape.buffer.add(row);
107 }
108
109 public Value[] next() throws SQLException {
110 return sort != null ? nextSorted() : nextUnsorted();
111 }
112
113 private Value[] nextUnsorted() throws SQLException {
114 file.seek(mainTape.pos);
115 if (mainTape.buffer.size() == 0) {
116 for (int j = 0; mainTape.pos < mainTape.end && j < READ_AHEAD; j++) {
117 readRow(mainTape);
118 }
119 }
120 Value[] row = (Value[]) mainTape.buffer.get(0);
121 mainTape.buffer.remove(0);
122 return row;
123 }
124
125 private Value[] nextSorted() throws SQLException {
126 int next = -1;
127 for (int i = 0; i < tapes.size(); i++) {
128 ResultDiskTape tape = getTape(i);
129 if (tape.buffer.size() == 0 && tape.pos < tape.end) {
130 file.seek(tape.pos);
131 for (int j = 0; tape.pos < tape.end && j < READ_AHEAD; j++) {
132 readRow(tape);
133 }
134 }
135 if (tape.buffer.size() > 0) {
136 if (next == -1) {
137 next = i;
138 } else if (compareTapes(tape, getTape(next)) < 0) {
139 next = i;
140 }
141 }
142 }
143 ResultDiskTape t = getTape(next);
144 Value[] row = (Value[]) t.buffer.get(0);
145 t.buffer.remove(0);
146 return row;
147 }
148
149 private ResultDiskTape getTape(int i) {
150 return (ResultDiskTape) tapes.get(i);
151 }
152
153 private int compareTapes(ResultDiskTape a, ResultDiskTape b) throws SQLException {
154 Value[] va = (Value[]) a.buffer.get(0);
155 Value[] vb = (Value[]) b.buffer.get(0);
156 return sort.compare(va, vb);
157 }
158
159 protected void finalize() {
160 if(!Constants.RUN_FINALIZERS) {
161 return;
162 }
163 close();
164 }
165
166 public void close() {
167 if (file != null) {
168 file.closeAndDeleteSilently();
169 file = null;
170 }
171 }
172
173 }
174 |
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