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1
5 package org.h2.store;
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.message.Message;
13 import org.h2.util.ObjectArray;
14
15 public class UndoLog {
16 private Session session;
17 private Database database;
18 private ObjectArray records = new ObjectArray();
20 private FileStore file;
21 private DataPage rowBuff;
22 private int memoryUndo;
23
24 public UndoLog(Session session) {
25 this.session = session;
26 this.database = session.getDatabase();
27 }
28
29 public int size() {
30 if(Constants.CHECK && memoryUndo > records.size()) {
31 throw Message.getInternalError();
32 }
33 return records.size();
34 }
35
36 public void clear() {
37 records.clear();
38 memoryUndo = 0;
39 if(file != null) {
40 file.closeAndDeleteSilently();
41 file = null;
42 rowBuff = null;
43 }
44 }
45
46 public UndoLogRecord getAndRemoveLast() throws SQLException {
47 int i = records.size() - 1;
48 UndoLogRecord entry = (UndoLogRecord) records.get(i);
49 if(entry.isStored()) {
50 int start = Math.max(0, i-database.getMaxMemoryUndo()/2);
51 UndoLogRecord first = null;
52 for(int j=start; j<=i; j++) {
53 UndoLogRecord e = (UndoLogRecord) records.get(j);
54 if(e.isStored()) {
55 e.load(rowBuff, file, session);
56 memoryUndo++;
57 if(first == null) {
58 first = e;
59 }
60 }
61 }
62 first.seek(file);
63 }
64 records.remove(i);
65 memoryUndo--;
66 return entry;
67 }
68
69 public void add(UndoLogRecord entry) throws SQLException {
70 records.add(entry);
71 memoryUndo++;
72 if(memoryUndo > database.getMaxMemoryUndo() && database.isPersistent()) {
73 if(file == null) {
74 String fileName = database.createTempFile();
75 file = database.openFile(fileName, false);
76 file.autoDelete();
77 file.seek(FileStore.HEADER_LENGTH);
78 rowBuff = DataPage.create(database, Constants.DEFAULT_DATA_PAGE_SIZE);
79 }
80 DataPage buff = rowBuff;
81 for(int i=0; i<records.size(); i++) {
82 UndoLogRecord r = (UndoLogRecord) records.get(i);
83 if(!r.isStored() && r.canStore()) {
84 r.save(buff, file);
85 memoryUndo--;
86 }
87 }
88 }
89 }
90
91 }
92 |
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