| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.iapi.store.access.DiskHashtable |
| 4 | |
| 5 | Copyright 2005 The Apache Software Foundation or its licensors, as applicable. |
| 6 | |
| 7 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | you may not use this file except in compliance with the License. |
| 9 | You may obtain a copy of the License at |
| 10 | |
| 11 | http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | |
| 13 | Unless required by applicable law or agreed to in writing, software |
| 14 | distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | See the License for the specific language governing permissions and |
| 17 | limitations under the License. |
| 18 | |
| 19 | */ |
| 20 | |
| 21 | package org.apache.derby.iapi.store.access; |
| 22 | |
| 23 | import java.util.Enumeration; |
| 24 | import java.util.NoSuchElementException; |
| 25 | import java.util.Properties; |
| 26 | import java.util.Vector; |
| 27 | import org.apache.derby.iapi.error.StandardException; |
| 28 | import org.apache.derby.iapi.services.io.FormatableBitSet; |
| 29 | import org.apache.derby.iapi.types.DataValueDescriptor; |
| 30 | import org.apache.derby.iapi.types.SQLInteger; |
| 31 | import org.apache.derby.impl.store.access.heap.HeapRowLocation; |
| 32 | import org.apache.derby.iapi.types.RowLocation; |
| 33 | import org.apache.derby.iapi.services.context.ContextService; |
| 34 | import org.apache.derby.iapi.sql.conn.LanguageConnectionContext; |
| 35 | |
| 36 | /** |
| 37 | * This class is used by BackingStoreHashtable when the BackingStoreHashtable must spill to disk. |
| 38 | * It implements the methods of a hash table: put, get, remove, elements, however it is not implemented |
| 39 | * as a hash table. In order to minimize the amount of unique code it is implemented using a Btree and a heap |
| 40 | * conglomerate. The Btree indexes the hash code of the row key. The actual key may be too long for |
| 41 | * our Btree implementation. |
| 42 | * |
| 43 | * Created: Fri Jan 28 13:58:03 2005 |
| 44 | * |
| 45 | * @author <a href="mailto:klebanof@us.ibm.com">Jack Klebanoff</a> |
| 46 | * @version 1.0 |
| 47 | */ |
| 48 | |
| 49 | public class DiskHashtable |
| 50 | { |
| 51 | private final long rowConglomerateId; |
| 52 | private ConglomerateController rowConglomerate; |
| 53 | private final long btreeConglomerateId; |
| 54 | private ConglomerateController btreeConglomerate; |
| 55 | private final DataValueDescriptor[] btreeRow; |
| 56 | private final int[] key_column_numbers; |
| 57 | private final boolean remove_duplicates; |
| 58 | private final TransactionController tc; |
| 59 | private final DataValueDescriptor[] row; |
| 60 | private final DataValueDescriptor[] scanKey = { new SQLInteger()}; |
| 61 | private int size; |
| 62 | private boolean keepStatistics; |
| 63 | |
| 64 | /** |
| 65 | * Creates a new <code>DiskHashtable</code> instance. |
| 66 | * |
| 67 | * @param tc |
| 68 | * @param template An array of DataValueDescriptors that serves as a template for the rows. |
| 69 | * @param key_column_numbers The indexes of the key columns (0 based) |
| 70 | * @param remove_duplicates If true then rows with duplicate keys are removed |
| 71 | * @param keepAfterCommit If true then the hash table is kept after a commit |
| 72 | */ |
| 73 | public DiskHashtable( TransactionController tc, |
| 74 | DataValueDescriptor[] template, |
| 75 | int[] key_column_numbers, |
| 76 | boolean remove_duplicates, |
| 77 | boolean keepAfterCommit) |
| 78 | throws StandardException |
| 79 | { |
| 80 | this.tc = tc; |
| 81 | this.key_column_numbers = key_column_numbers; |
| 82 | this.remove_duplicates = remove_duplicates; |
| 83 | LanguageConnectionContext lcc = (LanguageConnectionContext) |
| 84 | ContextService.getContextOrNull(LanguageConnectionContext.CONTEXT_ID); |
| 85 | keepStatistics = (lcc != null) && lcc.getRunTimeStatisticsMode(); |
| 86 | row = new DataValueDescriptor[ template.length]; |
| 87 | for( int i = 0; i < row.length; i++) |
| 88 | row[i] = template[i].getNewNull(); |
| 89 | int tempFlags = keepAfterCommit ? (TransactionController.IS_TEMPORARY | TransactionController.IS_KEPT) |
| 90 | : TransactionController.IS_TEMPORARY; |
| 91 | |
| 92 | rowConglomerateId = tc.createConglomerate( "heap", |
| 93 | template, |
| 94 | (ColumnOrdering[]) null, |
| 95 | (Properties) null, |
| 96 | tempFlags); |
| 97 | rowConglomerate = tc.openConglomerate( rowConglomerateId, |
| 98 | keepAfterCommit, |
| 99 | TransactionController.OPENMODE_FORUPDATE, |
| 100 | TransactionController.MODE_TABLE, |
| 101 | TransactionController.ISOLATION_NOLOCK /* Single thread only */ ); |
| 102 | |
| 103 | btreeRow = new DataValueDescriptor[] { new SQLInteger(), rowConglomerate.newRowLocationTemplate()}; |
| 104 | Properties btreeProps = new Properties(); |
| 105 | btreeProps.put( "baseConglomerateId", String.valueOf( rowConglomerateId)); |
| 106 | btreeProps.put( "rowLocationColumn", "1"); |
| 107 | btreeProps.put( "allowDuplicates", "false"); // Because the row location is part of the key |
| 108 | btreeProps.put( "nKeyFields", "2"); // Include the row location column |
| 109 | btreeProps.put( "nUniqueColumns", "2"); // Include the row location column |
| 110 | btreeProps.put( "maintainParentLinks", "false"); |
| 111 | btreeConglomerateId = tc.createConglomerate( "BTREE", |
| 112 | btreeRow, |
| 113 | (ColumnOrdering[]) null, |
| 114 | btreeProps, |
| 115 | tempFlags); |
| 116 | |
| 117 | btreeConglomerate = tc.openConglomerate( btreeConglomerateId, |
| 118 | keepAfterCommit, |
| 119 | TransactionController.OPENMODE_FORUPDATE, |
| 120 | TransactionController.MODE_TABLE, |
| 121 | TransactionController.ISOLATION_NOLOCK /* Single thread only */ ); |
| 122 | } // end of constructor |
| 123 | |
| 124 | public void close() throws StandardException |
| 125 | { |
| 126 | btreeConglomerate.close(); |
| 127 | rowConglomerate.close(); |
| 128 | tc.dropConglomerate( btreeConglomerateId); |
| 129 | tc.dropConglomerate( rowConglomerateId); |
| 130 | } // end of close |
| 131 | |
| 132 | /** |
| 133 | * Put a new row in the overflow structure. |
| 134 | * |
| 135 | * @param row The row to be inserted. |
| 136 | * |
| 137 | * @return true if the row was added, |
| 138 | * false if it was not added (because it was a duplicate and we are eliminating duplicates). |
| 139 | * |
| 140 | * @exception StandardException standard error policy |
| 141 | */ |
| 142 | public boolean put( Object key, Object[] row) |
| 143 | throws StandardException |
| 144 | { |
| 145 | boolean isDuplicate = false; |
| 146 | if( remove_duplicates || keepStatistics) |
| 147 | { |
| 148 | // Go to the work of finding out whether it is a duplicate |
| 149 | isDuplicate = (getRemove( key, false, true) != null); |
| 150 | if( remove_duplicates && isDuplicate) |
| 151 | return false; |
| 152 | } |
| 153 | rowConglomerate.insertAndFetchLocation( (DataValueDescriptor[]) row, (RowLocation) btreeRow[1]); |
| 154 | btreeRow[0].setValue( key.hashCode()); |
| 155 | btreeConglomerate.insert( btreeRow); |
| 156 | if( keepStatistics && !isDuplicate) |
| 157 | size++; |
| 158 | return true; |
| 159 | } // end of put |
| 160 | |
| 161 | /** |
| 162 | * Get a row from the overflow structure. |
| 163 | * |
| 164 | * @param key If the rows only have one key column then the key value. If there is more than one |
| 165 | * key column then a KeyHasher |
| 166 | * |
| 167 | * @return null if there is no corresponding row, |
| 168 | * the row (DataValueDescriptor[]) if there is exactly one row with the key |
| 169 | * a Vector of all the rows with the key if there is more than one. |
| 170 | * |
| 171 | * @exception StandardException |
| 172 | */ |
| 173 | public Object get( Object key) |
| 174 | throws StandardException |
| 175 | { |
| 176 | return getRemove( key, false, false); |
| 177 | } |
| 178 | |
| 179 | private Object getRemove( Object key, boolean remove, boolean existenceOnly) |
| 180 | throws StandardException |
| 181 | { |
| 182 | int hashCode = key.hashCode(); |
| 183 | int rowCount = 0; |
| 184 | Object retValue = null; |
| 185 | |
| 186 | scanKey[0].setValue( hashCode); |
| 187 | ScanController scan = tc.openScan( btreeConglomerateId, |
| 188 | false, // do not hold |
| 189 | remove ? TransactionController.OPENMODE_FORUPDATE : 0, |
| 190 | TransactionController.MODE_TABLE, |
| 191 | TransactionController.ISOLATION_READ_UNCOMMITTED, |
| 192 | null, // Scan all the columns |
| 193 | scanKey, |
| 194 | ScanController.GE, |
| 195 | (Qualifier[][]) null, |
| 196 | scanKey, |
| 197 | ScanController.GT); |
| 198 | try |
| 199 | { |
| 200 | while( scan.fetchNext( btreeRow)) |
| 201 | { |
| 202 | if( rowConglomerate.fetch( (RowLocation) btreeRow[1], row, (FormatableBitSet) null /* all columns */) |
| 203 | && rowMatches( row, key)) |
| 204 | { |
| 205 | if( existenceOnly) |
| 206 | return this; |
| 207 | |
| 208 | rowCount++; |
| 209 | if( rowCount == 1) |
| 210 | retValue = BackingStoreHashtable.cloneRow( row); |
| 211 | else |
| 212 | { |
| 213 | Vector v; |
| 214 | if( rowCount == 2) |
| 215 | { |
| 216 | v = new Vector( 2); |
| 217 | v.add( retValue); |
| 218 | retValue = v; |
| 219 | } |
| 220 | else |
| 221 | v = (Vector) retValue; |
| 222 | v.add( BackingStoreHashtable.cloneRow( row)); |
| 223 | } |
| 224 | if( remove) |
| 225 | { |
| 226 | rowConglomerate.delete( (RowLocation) btreeRow[1]); |
| 227 | scan.delete(); |
| 228 | size--; |
| 229 | } |
| 230 | if( remove_duplicates) |
| 231 | // This must be the only row with the key |
| 232 | return retValue; |
| 233 | } |
| 234 | } |
| 235 | } |
| 236 | finally |
| 237 | { |
| 238 | scan.close(); |
| 239 | } |
| 240 | return retValue; |
| 241 | } // end of getRemove |
| 242 | |
| 243 | |
| 244 | private boolean rowMatches( DataValueDescriptor[] row, |
| 245 | Object key) |
| 246 | { |
| 247 | if( key_column_numbers.length == 1) |
| 248 | return row[ key_column_numbers[0]].equals( key); |
| 249 | |
| 250 | KeyHasher kh = (KeyHasher) key; |
| 251 | for( int i = 0; i < key_column_numbers.length; i++) |
| 252 | { |
| 253 | if( ! row[ key_column_numbers[i]].equals( kh.getObject(i))) |
| 254 | return false; |
| 255 | } |
| 256 | return true; |
| 257 | } // end of rowMatches |
| 258 | |
| 259 | /** |
| 260 | * remove all rows with a given key from the hash table. |
| 261 | * |
| 262 | * @param key The key of the rows to remove. |
| 263 | * |
| 264 | * @return The removed row(s). |
| 265 | * |
| 266 | * @exception StandardException Standard exception policy. |
| 267 | **/ |
| 268 | public Object remove( Object key) |
| 269 | throws StandardException |
| 270 | { |
| 271 | return getRemove( key, true, false); |
| 272 | } // end of remove |
| 273 | |
| 274 | /** |
| 275 | * @return The number of rows in the hash table |
| 276 | */ |
| 277 | public int size() |
| 278 | { |
| 279 | return size; |
| 280 | } |
| 281 | |
| 282 | /** |
| 283 | * Return an Enumeration that can be used to scan entire table. |
| 284 | * <p> |
| 285 | * RESOLVE - is it worth it to support this routine? |
| 286 | * |
| 287 | * @return The Enumeration. |
| 288 | * |
| 289 | * @exception StandardException Standard exception policy. |
| 290 | **/ |
| 291 | public Enumeration elements() |
| 292 | throws StandardException |
| 293 | { |
| 294 | return new ElementEnum(); |
| 295 | } |
| 296 | |
| 297 | private class ElementEnum implements Enumeration |
| 298 | { |
| 299 | private ScanController scan; |
| 300 | private boolean hasMore; |
| 301 | |
| 302 | ElementEnum() |
| 303 | { |
| 304 | try |
| 305 | { |
| 306 | scan = tc.openScan( rowConglomerateId, |
| 307 | false, // do not hold |
| 308 | 0, // read only |
| 309 | TransactionController.MODE_TABLE, |
| 310 | TransactionController.ISOLATION_NOLOCK, |
| 311 | (FormatableBitSet) null, // all columns |
| 312 | (DataValueDescriptor[]) null, // no start key |
| 313 | 0, // no start key operator |
| 314 | (Qualifier[][]) null, |
| 315 | (DataValueDescriptor[]) null, // no stop key |
| 316 | 0 /* no stop key operator */); |
| 317 | hasMore = scan.next(); |
| 318 | if( ! hasMore) |
| 319 | { |
| 320 | scan.close(); |
| 321 | scan = null; |
| 322 | } |
| 323 | } |
| 324 | catch( StandardException se) |
| 325 | { |
| 326 | hasMore = false; |
| 327 | if( scan != null) |
| 328 | { |
| 329 | try |
| 330 | { |
| 331 | scan.close(); |
| 332 | } |
| 333 | catch( StandardException se1){}; |
| 334 | scan = null; |
| 335 | } |
| 336 | } |
| 337 | } // end of constructor |
| 338 | |
| 339 | public boolean hasMoreElements() |
| 340 | { |
| 341 | return hasMore; |
| 342 | } |
| 343 | |
| 344 | public Object nextElement() |
| 345 | { |
| 346 | if( ! hasMore) |
| 347 | throw new NoSuchElementException(); |
| 348 | try |
| 349 | { |
| 350 | scan.fetch( row); |
| 351 | Object retValue = BackingStoreHashtable.cloneRow( row); |
| 352 | hasMore = scan.next(); |
| 353 | if( ! hasMore) |
| 354 | { |
| 355 | scan.close(); |
| 356 | scan = null; |
| 357 | } |
| 358 | |
| 359 | return retValue; |
| 360 | } |
| 361 | catch( StandardException se) |
| 362 | { |
| 363 | if( scan != null) |
| 364 | { |
| 365 | try |
| 366 | { |
| 367 | scan.close(); |
| 368 | } |
| 369 | catch( StandardException se1){}; |
| 370 | scan = null; |
| 371 | } |
| 372 | throw new NoSuchElementException(); |
| 373 | } |
| 374 | } // end of nextElement |
| 375 | } // end of class ElementEnum |
| 376 | } |