1 | package org.mapdb;
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2 |
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3 | import java.util.LinkedHashSet;
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4 | import java.util.Set;
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5 |
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6 | /**
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7 | * Transaction factory
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8 | *
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9 | * @author Jan Kotek
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10 | */
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11 | public class TxMaker {
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12 |
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13 | protected static final Fun.Tuple2<Object, Serializer> DELETED = new Fun.Tuple2(null, Serializer.STRING_SERIALIZER);
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14 |
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15 | protected Engine engine;
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16 |
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17 | protected final Object lock = new Object();
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18 |
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19 | protected final LongMap<TxEngine> globalMod = new LongHashMap<TxEngine>();
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20 |
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21 |
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22 | public TxMaker(Engine engine) {
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23 | if(engine==null) throw new IllegalArgumentException();
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24 | this.engine = engine;
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25 | }
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26 |
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27 |
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28 | public DB makeTx(){
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29 | return new DB(new TxEngine(engine));
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30 | }
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31 |
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32 | public void close() {
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33 | if(engine==null)
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34 | engine.close();
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35 | }
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36 |
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37 | /**
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38 | * Executes given block withing single transaction.
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39 | * If block throws {@code TxRollbackException} execution is repeated until it does not fail.
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40 | *
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41 | * @param txBlock
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42 | */
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43 | public void execute(TxBlock txBlock) {
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44 | for(;;){
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45 | DB tx = makeTx();
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46 | try{
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47 | txBlock.tx(tx);
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48 | if(!tx.isClosed())
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49 | tx.commit();
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50 | return;
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51 | }catch(TxRollbackException e){
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52 | //failed, so try again
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53 | }
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54 | }
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55 | }
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56 |
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57 | protected class TxEngine extends EngineWrapper{
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58 |
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59 | protected LongMap<Fun.Tuple2<?, Serializer>> modItems =
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60 | new LongHashMap<Fun.Tuple2<?, Serializer>>();
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61 |
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62 | protected Set<Long> newItems = new LinkedHashSet<Long>();
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63 |
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64 |
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65 | protected TxEngine(Engine engine) {
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66 | super(engine);
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67 | }
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68 |
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69 | @Override
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70 | public <A> long put(A value, Serializer<A> serializer) {
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71 | if(isClosed()) throw new IllegalAccessError("already closed");
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72 | synchronized (lock){
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73 | long recid = engine.put(Utils.EMPTY_STRING, Serializer.EMPTY_SERIALIZER);
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74 | newItems.add(recid);
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75 | modItems.put(recid, Fun.t2(value, (Serializer)serializer));
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76 | globalMod.put(recid, TxEngine.this);
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77 | return recid;
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78 | }
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79 | }
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80 |
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81 | @Override
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82 | public <A> A get(long recid, Serializer<A> serializer) {
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83 | if(isClosed()) throw new IllegalAccessError("already closed");
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84 | synchronized (lock){
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85 | Fun.Tuple2 t = modItems.get(recid);
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86 | if(t!=null){
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87 | return (A) t.a;
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88 | //TODO compare serializers?
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89 | }else{
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90 | return super.get(recid, serializer);
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91 | }
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92 | }
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93 | }
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94 |
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95 | @Override
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96 | public <A> void update(long recid, A value, Serializer<A> serializer) {
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97 | if(isClosed()) throw new IllegalAccessError("already closed");
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98 | synchronized (lock){
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99 | TxEngine other = globalMod.get(recid);
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100 | if(other!=null && other!=TxEngine.this) {
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101 | rollback();
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102 | throw new TxRollbackException();
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103 | }
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104 | modItems.put(recid, new Fun.Tuple2(value, serializer));
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105 | globalMod.put(recid, TxEngine.this);
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106 | }
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107 |
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108 | }
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109 |
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110 | @Override
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111 | public <A> boolean compareAndSwap(long recid, A expectedOldValue, A newValue, Serializer<A> serializer) {
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112 | if(isClosed()) throw new IllegalAccessError("already closed");
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113 | throw new IllegalAccessError("Compare and Swap not supported in Tx mode");
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114 | }
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115 |
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116 | @Override
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117 | public <A> void delete(long recid, Serializer<A> serializer){
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118 | if(isClosed()) throw new IllegalAccessError("already closed");
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119 | synchronized (lock){
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120 | TxEngine other = globalMod.get(recid);
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121 | if(other!=null && other!=TxEngine.this) {
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122 | rollback();
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123 | throw new TxRollbackException();
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124 | }
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125 | modItems.put(recid, DELETED);
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126 | globalMod.put(recid, TxEngine.this);
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127 | }
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128 | }
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129 |
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130 | @Override
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131 | public void commit() {
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132 | synchronized (lock){
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133 | //remove locally modified items from global list
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134 | LongMap.LongMapIterator<Fun.Tuple2<?, Serializer>> iter = modItems.longMapIterator();
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135 | while(iter.moveToNext()){
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136 | TxEngine other = globalMod.remove(iter.key());
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137 | if(other!=TxEngine.this) throw new InternalError();
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138 | Fun.Tuple2<?, Serializer> t = iter.value();
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139 | engine.update(iter.key(), t.a, t.b);
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140 | }
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141 | modItems = null;
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142 | newItems = null;
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143 |
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144 | engine.commit();
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145 | }
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146 |
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147 | }
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148 |
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149 | @Override
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150 | public void rollback() {
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151 | synchronized (lock){
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152 | //remove locally modified items from global list
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153 | LongMap.LongMapIterator iter = modItems.longMapIterator();
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154 | while(iter.moveToNext()){
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155 | TxEngine other = globalMod.remove(iter.key());
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156 | if(other!=TxEngine.this) throw new InternalError();
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157 | }
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158 | //delete preallocated items
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159 | for(long recid:newItems){
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160 | engine.delete(recid, Serializer.EMPTY_SERIALIZER);
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161 | }
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162 | modItems = null;
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163 | newItems = null;
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164 | }
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165 |
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166 | }
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167 |
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168 | @Override
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169 | public void close() {
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170 | rollback();
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171 | }
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172 | }
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173 |
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174 |
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175 | }
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