| 1 | /* |
| 2 | |
| 3 | Derby - Class org.apache.derby.impl.store.raw.log.Scan |
| 4 | |
| 5 | Copyright 1997, 2004 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.impl.store.raw.log; |
| 22 | |
| 23 | import org.apache.derby.iapi.reference.SQLState; |
| 24 | |
| 25 | import org.apache.derby.iapi.services.io.ArrayInputStream; |
| 26 | |
| 27 | import org.apache.derby.iapi.services.sanity.SanityManager; |
| 28 | |
| 29 | import org.apache.derby.iapi.error.StandardException; |
| 30 | |
| 31 | import org.apache.derby.iapi.store.raw.log.LogInstant; |
| 32 | |
| 33 | import org.apache.derby.iapi.store.raw.xact.TransactionId; |
| 34 | |
| 35 | import org.apache.derby.impl.store.raw.log.LogCounter; |
| 36 | import org.apache.derby.impl.store.raw.log.LogRecord; |
| 37 | import org.apache.derby.impl.store.raw.log.StreamLogScan; |
| 38 | |
| 39 | import org.apache.derby.io.StorageRandomAccessFile; |
| 40 | |
| 41 | import java.io.IOException; |
| 42 | import org.apache.derby.iapi.store.raw.Loggable; |
| 43 | |
| 44 | /** |
| 45 | |
| 46 | Scan the the log which is implemented by a series of log files.n |
| 47 | This log scan knows how to move across log file if it is positioned at |
| 48 | the boundary of a log file and needs to getNextRecord. |
| 49 | |
| 50 | <PRE> |
| 51 | 4 bytes - length of user data, i.e. N |
| 52 | 8 bytes - long representing log instant |
| 53 | N bytes of supplied data |
| 54 | 4 bytes - length of user data, i.e. N |
| 55 | </PRE> |
| 56 | |
| 57 | */ |
| 58 | |
| 59 | public class Scan implements StreamLogScan { |
| 60 | |
| 61 | // value for scanDirection |
| 62 | public static final byte FORWARD = 1; |
| 63 | public static final byte BACKWARD = 2; |
| 64 | public static final byte BACKWARD_FROM_LOG_END = 4; |
| 65 | |
| 66 | private StorageRandomAccessFile scan; // an output stream to the log file |
| 67 | private LogToFile logFactory; // log factory knows how to to skip |
| 68 | // from log file to log file |
| 69 | |
| 70 | private long currentLogFileNumber; // the log file the scan is currently on |
| 71 | |
| 72 | private long currentLogFileLength; // the size of the current log file |
| 73 | // used only for FORWARD scan to determine when |
| 74 | // to switch the next log file |
| 75 | |
| 76 | private long knownGoodLogEnd; // For FORWARD scan only |
| 77 | // during recovery, we need to determine the end |
| 78 | // of the log. Everytime a complete log record |
| 79 | // is read in, knownGoodLogEnd is set to the |
| 80 | // log instant of the next log record if it is |
| 81 | // on the same log file. |
| 82 | // |
| 83 | // only valid afer a successfull getNextRecord |
| 84 | // on a FOWARD scan. |
| 85 | |
| 86 | |
| 87 | private long currentInstant; // the log instant the scan is |
| 88 | // currently on - only valid after a |
| 89 | // successful getNextRecord |
| 90 | |
| 91 | private long stopAt; // scan until we find a log record whose |
| 92 | // log instance < stopAt if we scan BACKWARD |
| 93 | // log instance > stopAt if we scan FORWARD |
| 94 | // log instance >= stopAt if we scan FORWARD_FLUSHED |
| 95 | |
| 96 | |
| 97 | private byte scanDirection; // BACKWARD or FORWARD |
| 98 | |
| 99 | private boolean fuzzyLogEnd = false; //get sets to true during forward scan |
| 100 | //for recovery, if there were |
| 101 | //partial writes at the end of the log before crash; |
| 102 | //during forward scan for recovery. |
| 103 | |
| 104 | |
| 105 | /** |
| 106 | For backward scan, we expect a scan positioned at the end of the next log record. |
| 107 | For forward scan, we expect a scan positioned at the beginning of the next log record. |
| 108 | |
| 109 | For forward flushed scan, we expect stopAt to be the instant for the |
| 110 | first not-flushed log record. Like any forward scan, we expect a scan |
| 111 | positioned at the beginning of the next log record. |
| 112 | |
| 113 | @exception StandardException Standard Cloudscape error policy |
| 114 | @exception IOException cannot access the log at the new position. |
| 115 | */ |
| 116 | public Scan(LogToFile logFactory, long startAt, LogInstant stopAt, byte direction) |
| 117 | throws IOException, StandardException |
| 118 | { |
| 119 | if (SanityManager.DEBUG) |
| 120 | SanityManager.ASSERT(startAt != LogCounter.INVALID_LOG_INSTANT, |
| 121 | "cannot start scan on an invalid log instant"); |
| 122 | |
| 123 | this.logFactory = logFactory; |
| 124 | currentLogFileNumber = LogCounter.getLogFileNumber(startAt); |
| 125 | currentLogFileLength = -1; |
| 126 | knownGoodLogEnd = LogCounter.INVALID_LOG_INSTANT;// set at getNextRecord for FORWARD scan |
| 127 | currentInstant = LogCounter.INVALID_LOG_INSTANT; // set at getNextRecord |
| 128 | if (stopAt != null) |
| 129 | this.stopAt = ((LogCounter) stopAt).getValueAsLong(); |
| 130 | else |
| 131 | this.stopAt = LogCounter.INVALID_LOG_INSTANT; |
| 132 | |
| 133 | switch(direction) |
| 134 | { |
| 135 | case FORWARD: |
| 136 | scan = logFactory.getLogFileAtPosition(startAt); |
| 137 | scanDirection = FORWARD; |
| 138 | |
| 139 | if (SanityManager.DEBUG) |
| 140 | if (scan == null) |
| 141 | SanityManager.THROWASSERT( |
| 142 | "scan null at " + LogCounter.toDebugString(startAt)); |
| 143 | |
| 144 | // NOTE: just get the length of the file without syncing. |
| 145 | // this only works because the only place forward scan is used |
| 146 | // right now is on recovery redo and nothing is being added to |
| 147 | // the current log file. When the forward scan is used for some |
| 148 | // other purpose, need to sync access to the end of the log |
| 149 | currentLogFileLength = scan.length(); |
| 150 | break; |
| 151 | |
| 152 | case BACKWARD: |
| 153 | // startAt is at the front of the log record, for backward |
| 154 | // scan we need to be positioned at the end of the log record |
| 155 | scan = logFactory.getLogFileAtPosition(startAt); |
| 156 | int logsize = scan.readInt(); |
| 157 | |
| 158 | // skip forward over the log record and all the overhead, but remember |
| 159 | // we just read an int off the overhead |
| 160 | scan.seek(scan.getFilePointer() + logsize + LogToFile.LOG_RECORD_OVERHEAD - 4); |
| 161 | scanDirection = BACKWARD; |
| 162 | break; |
| 163 | |
| 164 | case BACKWARD_FROM_LOG_END: |
| 165 | // startAt is at the end of the log, no need to skip the log record |
| 166 | scan = logFactory.getLogFileAtPosition(startAt); |
| 167 | scanDirection = BACKWARD; |
| 168 | break; |
| 169 | |
| 170 | } |
| 171 | } |
| 172 | |
| 173 | /* |
| 174 | ** Methods of StreamLogScan |
| 175 | */ |
| 176 | |
| 177 | /** |
| 178 | Read the next log record. |
| 179 | Switching log to a previous log file if necessary, |
| 180 | Resize the input stream byte array if necessary. |
| 181 | @see StreamLogScan#getNextRecord |
| 182 | |
| 183 | @return the next LogRecord, or null if the end of the |
| 184 | scan has been reached. |
| 185 | |
| 186 | @exception StandardException Standard Cloudscape error policy |
| 187 | */ |
| 188 | public LogRecord getNextRecord(ArrayInputStream input, |
| 189 | TransactionId tranId, |
| 190 | int groupmask) |
| 191 | throws StandardException |
| 192 | { |
| 193 | if (scan == null) |
| 194 | return null; |
| 195 | |
| 196 | if (SanityManager.DEBUG) |
| 197 | SanityManager.ASSERT(scanDirection != 0, "scan has been secretly closed!"); |
| 198 | |
| 199 | LogRecord lr = null; |
| 200 | try |
| 201 | { |
| 202 | if (scanDirection == BACKWARD) |
| 203 | lr = getNextRecordBackward(input, tranId, groupmask); |
| 204 | else if (scanDirection == FORWARD) |
| 205 | lr = getNextRecordForward(input, tranId, groupmask); |
| 206 | |
| 207 | return lr; |
| 208 | |
| 209 | } |
| 210 | catch (IOException ioe) |
| 211 | { |
| 212 | if (SanityManager.DEBUG) |
| 213 | ioe.printStackTrace(); |
| 214 | |
| 215 | throw logFactory.markCorrupt( |
| 216 | StandardException.newException(SQLState.LOG_CORRUPTED, ioe)); |
| 217 | } |
| 218 | catch (ClassNotFoundException cnfe) |
| 219 | { |
| 220 | if (SanityManager.DEBUG) |
| 221 | cnfe.printStackTrace(); |
| 222 | |
| 223 | throw logFactory.markCorrupt( |
| 224 | StandardException.newException(SQLState.LOG_CORRUPTED, cnfe)); |
| 225 | } |
| 226 | finally |
| 227 | { |
| 228 | if (lr == null) |
| 229 | close(); // no more log record, close the scan |
| 230 | } |
| 231 | |
| 232 | } |
| 233 | |
| 234 | /** |
| 235 | Read the previous log record. |
| 236 | Switching log to a previous log file if necessary, |
| 237 | Resize the input stream byte array if necessary. |
| 238 | @see StreamLogScan#getNextRecord |
| 239 | |
| 240 | Side effects include: |
| 241 | on a successful read, setting currentInstant. |
| 242 | on a log file switch, setting currentLogFileNumber. |
| 243 | |
| 244 | @return the previous LogRecord, or null if the end of the |
| 245 | scan has been reached. |
| 246 | */ |
| 247 | private LogRecord getNextRecordBackward(ArrayInputStream input, |
| 248 | TransactionId tranId, |
| 249 | int groupmask) |
| 250 | throws StandardException, IOException, ClassNotFoundException |
| 251 | { |
| 252 | if (SanityManager.DEBUG) |
| 253 | SanityManager.ASSERT(scanDirection == BACKWARD, "can only called by backward scan"); |
| 254 | |
| 255 | // scan is positioned just past the last byte of the record, or |
| 256 | // right at the beginning of the file (end of the file header) |
| 257 | // may need to switch log file |
| 258 | |
| 259 | boolean candidate; |
| 260 | // if we have filtering, peek at the group and/or the transaction id, |
| 261 | // do them in one read rather than 2 reads. |
| 262 | int peekAmount = LogRecord.formatOverhead() + LogRecord.maxGroupStoredSize(); |
| 263 | if (tranId != null) |
| 264 | peekAmount += LogRecord.maxTransactionIdStoredSize(tranId); |
| 265 | |
| 266 | int readAmount; // the number of bytes actually read |
| 267 | |
| 268 | LogRecord lr; |
| 269 | long curpos = scan.getFilePointer(); |
| 270 | |
| 271 | do |
| 272 | { |
| 273 | // this log record is a candidate unless proven otherwise |
| 274 | candidate = true; |
| 275 | lr = null; |
| 276 | readAmount = -1; |
| 277 | |
| 278 | if (curpos == LogToFile.LOG_FILE_HEADER_SIZE) |
| 279 | { |
| 280 | // don't go thru the trouble of switching log file if we |
| 281 | // will have gone past stopAt |
| 282 | if (stopAt != LogCounter.INVALID_LOG_INSTANT && |
| 283 | LogCounter.getLogFileNumber(stopAt) == currentLogFileNumber) |
| 284 | { |
| 285 | if (SanityManager.DEBUG) |
| 286 | { |
| 287 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 288 | { |
| 289 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 290 | "stopping at " + currentLogFileNumber); |
| 291 | } |
| 292 | } |
| 293 | |
| 294 | return null; // no more log record |
| 295 | } |
| 296 | |
| 297 | // figure out where the last log record is in the previous |
| 298 | // log file |
| 299 | scan.seek(LogToFile.LOG_FILE_HEADER_PREVIOUS_LOG_INSTANT_OFFSET); |
| 300 | long previousLogInstant = scan.readLong(); |
| 301 | scan.close(); |
| 302 | |
| 303 | if (SanityManager.DEBUG) |
| 304 | { |
| 305 | SanityManager.ASSERT(previousLogInstant != LogCounter.INVALID_LOG_INSTANT, |
| 306 | "scanning backward beyond the first log file"); |
| 307 | if (currentLogFileNumber != |
| 308 | LogCounter.getLogFileNumber(previousLogInstant) + 1) |
| 309 | SanityManager.THROWASSERT( |
| 310 | "scanning backward but get incorrect log file number " + |
| 311 | "expected " + (currentLogFileNumber -1) + |
| 312 | "get " + |
| 313 | LogCounter.getLogFileNumber(previousLogInstant)); |
| 314 | |
| 315 | SanityManager.ASSERT(LogCounter.getLogFilePosition(previousLogInstant) > |
| 316 | LogToFile.LOG_FILE_HEADER_SIZE, |
| 317 | "scanning backward encounter completely empty log file"); |
| 318 | |
| 319 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 320 | "scanning backwards from log file " + |
| 321 | currentLogFileNumber + ", switch to (" + |
| 322 | LogCounter.getLogFileNumber(previousLogInstant) + "," + |
| 323 | LogCounter.getLogFilePosition(previousLogInstant) + ")" |
| 324 | ); |
| 325 | } |
| 326 | |
| 327 | // log file switch, set this.currentLogFileNumber |
| 328 | currentLogFileNumber = LogCounter.getLogFileNumber(previousLogInstant); |
| 329 | |
| 330 | scan = logFactory.getLogFileAtPosition(previousLogInstant); |
| 331 | |
| 332 | // scan is located right past the last byte of the last log |
| 333 | // record in the previous log file. currentLogFileNumber is |
| 334 | // set. We asserted that the scan is not located right at the |
| 335 | // end of the file header, in other words, there is at least |
| 336 | // one log record in this log file. |
| 337 | curpos = scan.getFilePointer(); |
| 338 | |
| 339 | // if the log file happens to be empty skip and proceed. |
| 340 | // ideally this case should never occur because log switch is |
| 341 | // not suppose to happen on an empty log file. |
| 342 | // But it is safer to put following check incase if it ever |
| 343 | // happens to avoid any recovery issues. |
| 344 | if (curpos == LogToFile.LOG_FILE_HEADER_SIZE) |
| 345 | continue; |
| 346 | } |
| 347 | |
| 348 | scan.seek(curpos - 4); |
| 349 | int recordLength = scan.readInt(); // get the length after the log record |
| 350 | |
| 351 | // calculate where this log record started. |
| 352 | // include the eight bytes for the long log instant at the front |
| 353 | // the four bytes of length in the front and the four bytes we just read |
| 354 | long recordStartPosition = curpos - recordLength - |
| 355 | LogToFile.LOG_RECORD_OVERHEAD; |
| 356 | |
| 357 | if (SanityManager.DEBUG) |
| 358 | { |
| 359 | if (recordStartPosition < LogToFile.LOG_FILE_HEADER_SIZE) |
| 360 | SanityManager.THROWASSERT( |
| 361 | "next position " + recordStartPosition + |
| 362 | " recordLength " + recordLength + |
| 363 | " current file position " + scan.getFilePointer()); |
| 364 | |
| 365 | scan.seek(recordStartPosition); |
| 366 | |
| 367 | // read the length before the log record and check it against the |
| 368 | // length after the log record |
| 369 | int checkLength = scan.readInt(); |
| 370 | |
| 371 | if (checkLength != recordLength) |
| 372 | { |
| 373 | long inst = LogCounter.makeLogInstantAsLong(currentLogFileNumber, recordStartPosition); |
| 374 | |
| 375 | throw logFactory.markCorrupt( |
| 376 | StandardException.newException( |
| 377 | SQLState.LOG_RECORD_CORRUPTED, |
| 378 | new Long(checkLength), |
| 379 | new Long(recordLength), |
| 380 | new Long(inst), |
| 381 | new Long(currentLogFileNumber))); |
| 382 | } |
| 383 | } |
| 384 | else |
| 385 | { |
| 386 | // skip over the length in insane |
| 387 | scan.seek(recordStartPosition+4); |
| 388 | } |
| 389 | |
| 390 | // scan is positioned just before the log instant |
| 391 | // read the current log instant - this is the currentInstant if we have not |
| 392 | // exceeded the scan limit |
| 393 | currentInstant = scan.readLong(); |
| 394 | |
| 395 | if (SanityManager.DEBUG) |
| 396 | { |
| 397 | // sanity check the current instant against the scan position |
| 398 | if (LogCounter.getLogFileNumber(currentInstant) != |
| 399 | currentLogFileNumber || |
| 400 | LogCounter.getLogFilePosition(currentInstant) != |
| 401 | recordStartPosition) |
| 402 | SanityManager.THROWASSERT( |
| 403 | "Wrong LogInstant on log record " + |
| 404 | LogCounter.toDebugString(currentInstant) + |
| 405 | " version real position (" + |
| 406 | currentLogFileNumber + "," + |
| 407 | recordStartPosition + ")"); |
| 408 | } |
| 409 | |
| 410 | |
| 411 | // if stopAt == INVALID_LOG_INSTANT, no stop instant, read till |
| 412 | // nothing more can be read. Else check scan limit |
| 413 | if (currentInstant < stopAt && stopAt != LogCounter.INVALID_LOG_INSTANT) |
| 414 | { |
| 415 | currentInstant = LogCounter.INVALID_LOG_INSTANT; |
| 416 | return null; // we went past the stopAt |
| 417 | } |
| 418 | |
| 419 | |
| 420 | byte[] data = input.getData(); |
| 421 | |
| 422 | if (data.length < recordLength) |
| 423 | { |
| 424 | // make a new array of sufficient size and reset the arrary |
| 425 | // in the input stream |
| 426 | data = new byte[recordLength]; |
| 427 | input.setData(data); |
| 428 | } |
| 429 | |
| 430 | // If the log is encrypted, we must do the filtering after reading |
| 431 | // and decrypting the record. |
| 432 | if (logFactory.databaseEncrypted()) |
| 433 | { |
| 434 | scan.readFully(data, 0, recordLength); |
| 435 | int len = logFactory.decrypt(data, 0, recordLength, data, 0); |
| 436 | if (SanityManager.DEBUG) |
| 437 | SanityManager.ASSERT(len == recordLength); |
| 438 | input.setLimit(0, recordLength); |
| 439 | } |
| 440 | else // no need to decrypt, only get the group and tid if we filter |
| 441 | { |
| 442 | if (groupmask == 0 && tranId == null) |
| 443 | { |
| 444 | // no filter, get the whole thing |
| 445 | scan.readFully(data, 0, recordLength); |
| 446 | input.setLimit(0, recordLength); |
| 447 | } |
| 448 | else |
| 449 | { |
| 450 | // Read only enough so that group and the tran id is in |
| 451 | // the data buffer. Group is stored as compressed int |
| 452 | // and tran id is stored as who knows what. read min |
| 453 | // of peekAmount or recordLength |
| 454 | readAmount = (recordLength > peekAmount) ? |
| 455 | peekAmount : recordLength; |
| 456 | |
| 457 | // in the data buffer, we now have enough to peek |
| 458 | scan.readFully(data, 0, readAmount); |
| 459 | input.setLimit(0, readAmount); |
| 460 | } |
| 461 | } |
| 462 | |
| 463 | lr = (LogRecord) input.readObject(); |
| 464 | |
| 465 | // skip the checksum log records, there is no need to look at them |
| 466 | // during backward scans. They are used only in forwardscan during recovery. |
| 467 | if(lr.isChecksum()) |
| 468 | { |
| 469 | candidate = false; |
| 470 | }else if (groupmask != 0 || tranId != null) |
| 471 | { |
| 472 | |
| 473 | // skip the checksum log records |
| 474 | if(lr.isChecksum()) |
| 475 | candidate = false; |
| 476 | |
| 477 | if (candidate && groupmask != 0 && (groupmask & lr.group()) == 0) |
| 478 | candidate = false; // no match, throw this log record out |
| 479 | |
| 480 | if (candidate && tranId != null) |
| 481 | { |
| 482 | TransactionId tid = lr.getTransactionId(); |
| 483 | if (!tid.equals(tranId)) // nomatch |
| 484 | candidate = false; // throw this log record out |
| 485 | } |
| 486 | |
| 487 | // if this log record is not filtered out, we need to read |
| 488 | // in the rest of the log record to the input buffer. |
| 489 | // Except if it is an encrypted database, in which case the |
| 490 | // entire log record have already be read in for |
| 491 | // decryption. |
| 492 | if (candidate && !logFactory.databaseEncrypted()) |
| 493 | { |
| 494 | // read the rest of the log into the buffer |
| 495 | if (SanityManager.DEBUG) |
| 496 | SanityManager.ASSERT(readAmount > 0); |
| 497 | |
| 498 | if (readAmount < recordLength) |
| 499 | { |
| 500 | // Need to remember where we are because the log |
| 501 | // record may have read part of it off the input |
| 502 | // stream already and that position is lost when we |
| 503 | // set limit again. |
| 504 | int inputPosition = input.getPosition(); |
| 505 | |
| 506 | scan.readFully(data, readAmount, |
| 507 | recordLength-readAmount); |
| 508 | |
| 509 | input.setLimit(0, recordLength); |
| 510 | input.setPosition(inputPosition); |
| 511 | } |
| 512 | } |
| 513 | } |
| 514 | |
| 515 | // go back to the start of the log record so that the next time |
| 516 | // this method is called, it is positioned right past the last byte |
| 517 | // of the record. |
| 518 | curpos = recordStartPosition; |
| 519 | scan.seek(curpos); |
| 520 | |
| 521 | } while (candidate == false); |
| 522 | |
| 523 | return lr; |
| 524 | |
| 525 | } |
| 526 | |
| 527 | /** |
| 528 | Read the next log record. |
| 529 | Switching log to a previous log file if necessary, |
| 530 | Resize the input stream byte array if necessary. |
| 531 | @see StreamLogScan#getNextRecord |
| 532 | |
| 533 | Side effects include: |
| 534 | on a successful read, setting currentInstant, knownGoodLogEnd |
| 535 | on a log file switch, setting currentLogFileNumber, currentLogFileLength. |
| 536 | on detecting a fuzzy log end that needs clearing, it will call |
| 537 | logFactory to clear the fuzzy log end. |
| 538 | |
| 539 | @return the next LogRecord, or null if the end of the |
| 540 | scan has been reached. |
| 541 | */ |
| 542 | private LogRecord getNextRecordForward(ArrayInputStream input, |
| 543 | TransactionId tranId, |
| 544 | int groupmask) |
| 545 | throws StandardException, IOException, ClassNotFoundException |
| 546 | { |
| 547 | if (SanityManager.DEBUG) |
| 548 | SanityManager.ASSERT(scanDirection == FORWARD, "can only called by forward scan"); |
| 549 | |
| 550 | // NOTE: |
| 551 | // |
| 552 | // if forward scan, scan is positioned at the first byte of the |
| 553 | // next record, or the end of file - note the the 'end of file' |
| 554 | // is defined at the time the scan is initialized. If we are |
| 555 | // on the current log file, it may well have grown by now... |
| 556 | // |
| 557 | // This is not a problem in reality because the only forward |
| 558 | // scan on the log now is recovery redo and the log does not |
| 559 | // grow. If in the future, a foward scan of the log is used |
| 560 | // for some other reasons, need to keep this in mind. |
| 561 | // |
| 562 | |
| 563 | // first we need to make sure the entire log record is on the |
| 564 | // log, or else this is a fuzzy log end. |
| 565 | |
| 566 | // RESOLVE: can get this from knownGoodLogEnd if this is not the first |
| 567 | // time getNext is called. Probably just as fast to call |
| 568 | // scan.getFilePointer though... |
| 569 | long recordStartPosition = scan.getFilePointer(); |
| 570 | |
| 571 | boolean candidate; |
| 572 | |
| 573 | // if we have filtering, peek at the group and/or the transaction id, |
| 574 | // do them in one read rather than 2 reads. |
| 575 | int peekAmount = LogRecord.formatOverhead() + LogRecord.maxGroupStoredSize(); |
| 576 | if (tranId != null) |
| 577 | peekAmount += LogRecord.maxTransactionIdStoredSize(tranId); |
| 578 | |
| 579 | int readAmount; // the number of bytes actually read |
| 580 | |
| 581 | LogRecord lr; |
| 582 | |
| 583 | do |
| 584 | { |
| 585 | // this log record is a candidate unless proven otherwise |
| 586 | candidate = true; |
| 587 | lr = null; |
| 588 | readAmount = -1; |
| 589 | |
| 590 | // if we are not right at the end but this position + 4 is at |
| 591 | // or exceeds the end, we know we don't have a complete log |
| 592 | // record. This is the log file and chalk it up as the fuzzy |
| 593 | // end. |
| 594 | if (recordStartPosition + 4 > currentLogFileLength) |
| 595 | { |
| 596 | // since there is no end of log file marker, we are at the |
| 597 | // end of the log. |
| 598 | if (SanityManager.DEBUG) |
| 599 | { |
| 600 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 601 | { |
| 602 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 603 | "detected fuzzy log end on log file " + |
| 604 | currentLogFileNumber + |
| 605 | " record start position " + recordStartPosition + |
| 606 | " file length " + currentLogFileLength); |
| 607 | } |
| 608 | } |
| 609 | |
| 610 | //if recordStartPosition == currentLogFileLength |
| 611 | //there is NO fuzz, it just a properly ended log |
| 612 | //without the end marker. |
| 613 | if(recordStartPosition != currentLogFileLength) |
| 614 | fuzzyLogEnd = true ; |
| 615 | |
| 616 | // don't bother to write the end of log file marker because |
| 617 | // if it is not overwritten by the next log record then |
| 618 | // the next time the database is recovered it will come |
| 619 | // back right here |
| 620 | return null; |
| 621 | } |
| 622 | |
| 623 | // read in the length before the log record |
| 624 | int recordLength = scan.readInt(); |
| 625 | |
| 626 | while (recordLength == 0 || recordStartPosition + recordLength + |
| 627 | LogToFile.LOG_RECORD_OVERHEAD > currentLogFileLength) |
| 628 | { |
| 629 | // if recordLength is zero or the log record goes beyond the |
| 630 | // current file, then we have detected the end of a log file. |
| 631 | // |
| 632 | // If recordLength == 0 then we know that this log file has either |
| 633 | // been properly switched or it had a 1/2 written log record which |
| 634 | // was subsequently cleared by clearFuzzyEnd. |
| 635 | // |
| 636 | // If recordLength != 0 but log record goes beyond the current log |
| 637 | // file, we have detected a fuzzy end. This is the last log file |
| 638 | // since we will clear it by clearFuzzyEnd. |
| 639 | |
| 640 | if (recordLength != 0) // this is a fuzzy log end |
| 641 | { |
| 642 | if (SanityManager.DEBUG) |
| 643 | { |
| 644 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 645 | { |
| 646 | SanityManager.DEBUG( |
| 647 | LogToFile.DBG_FLAG, |
| 648 | "detected fuzzy log end on log file " + |
| 649 | currentLogFileNumber + |
| 650 | " record start position " + |
| 651 | recordStartPosition + |
| 652 | " file length " + currentLogFileLength + |
| 653 | " recordLength=" + recordLength ); |
| 654 | } |
| 655 | } |
| 656 | |
| 657 | fuzzyLogEnd = true; |
| 658 | scan.close(); |
| 659 | scan = null; |
| 660 | |
| 661 | return null; |
| 662 | } |
| 663 | |
| 664 | // recordLength == 0 |
| 665 | |
| 666 | if (SanityManager.DEBUG) |
| 667 | { |
| 668 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 669 | { |
| 670 | if (recordStartPosition + 4 == currentLogFileLength) |
| 671 | { |
| 672 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 673 | "detected proper log end on log file " + |
| 674 | currentLogFileNumber); |
| 675 | } |
| 676 | else |
| 677 | { |
| 678 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 679 | "detected zapped log end on log file " + |
| 680 | currentLogFileNumber + |
| 681 | " end marker at " + |
| 682 | recordStartPosition + |
| 683 | " real end at " + currentLogFileLength); |
| 684 | } |
| 685 | } |
| 686 | } |
| 687 | |
| 688 | // don't go thru the trouble of switching log file if we |
| 689 | // have will have gone past stopAt if we want to stop here |
| 690 | if (stopAt != LogCounter.INVALID_LOG_INSTANT && |
| 691 | LogCounter.getLogFileNumber(stopAt) == currentLogFileNumber) |
| 692 | { |
| 693 | return null; |
| 694 | } |
| 695 | |
| 696 | // |
| 697 | // we have a log end marker and we don't want to stop yet, switch |
| 698 | // log file |
| 699 | // |
| 700 | scan.close(); |
| 701 | |
| 702 | // set this.currentLogFileNumber |
| 703 | scan = logFactory.getLogFileAtBeginning(++currentLogFileNumber); |
| 704 | if (scan == null) // we have seen the last log file |
| 705 | { |
| 706 | return null; |
| 707 | } |
| 708 | |
| 709 | // scan is position just past the log header |
| 710 | recordStartPosition = scan.getFilePointer(); |
| 711 | |
| 712 | // Verify that the header of the new log file refers |
| 713 | // to the end of the log record of the previous file |
| 714 | // (Rest of header has been verified by getLogFileAtBeginning) |
| 715 | scan.seek(LogToFile |
| 716 | .LOG_FILE_HEADER_PREVIOUS_LOG_INSTANT_OFFSET); |
| 717 | long previousLogInstant = scan.readLong(); |
| 718 | if (previousLogInstant != knownGoodLogEnd) { |
| 719 | // If there is a mismatch, something is wrong and |
| 720 | // we return null to stop the scan. The same |
| 721 | // behavior occurs when getLogFileAtBeginning |
| 722 | // detects an error in the other fields of the header. |
| 723 | if (SanityManager.DEBUG) { |
| 724 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) { |
| 725 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 726 | "log file " |
| 727 | + currentLogFileNumber |
| 728 | + ": previous log record: " |
| 729 | + previousLogInstant |
| 730 | + " known previous log record: " |
| 731 | + knownGoodLogEnd); |
| 732 | } |
| 733 | } |
| 734 | return null; |
| 735 | } |
| 736 | |
| 737 | |
| 738 | scan.seek(recordStartPosition); |
| 739 | |
| 740 | if (SanityManager.DEBUG) |
| 741 | { |
| 742 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 743 | { |
| 744 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 745 | "switched to next log file " + |
| 746 | currentLogFileNumber); |
| 747 | } |
| 748 | } |
| 749 | |
| 750 | // Advance knownGoodLogEnd to make sure that if this |
| 751 | // log file is the last log file and empty, logging |
| 752 | // continues in this file, not the old file. |
| 753 | knownGoodLogEnd = LogCounter.makeLogInstantAsLong |
| 754 | (currentLogFileNumber, recordStartPosition); |
| 755 | |
| 756 | // set this.currentLogFileLength |
| 757 | currentLogFileLength = scan.length(); |
| 758 | |
| 759 | if (recordStartPosition+4 >= currentLogFileLength) // empty log file |
| 760 | { |
| 761 | if (SanityManager.DEBUG) |
| 762 | { |
| 763 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 764 | { |
| 765 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 766 | "log file " + currentLogFileNumber + |
| 767 | " is empty"); |
| 768 | } |
| 769 | } |
| 770 | |
| 771 | return null; |
| 772 | } |
| 773 | |
| 774 | // we have successfully switched to the next log file. |
| 775 | // scan is positioned just before the next log record |
| 776 | // see if this one is written in entirety |
| 777 | recordLength = scan.readInt(); |
| 778 | } |
| 779 | |
| 780 | // we know the entire log record is on this log file |
| 781 | |
| 782 | // read the current log instant |
| 783 | currentInstant = scan.readLong(); |
| 784 | |
| 785 | /*check if the current instant happens is less than the last one. |
| 786 | *This can happen if system crashed before writing the log instant |
| 787 | *completely. If the instant is partially written it will be less |
| 788 | *than the last one and should be the last record that was suppose to |
| 789 | *get written. Currentlt preallocated files are filled with zeros, |
| 790 | *this should hold good. |
| 791 | *Note: In case of Non-preallocated files earlier check with log |
| 792 | * file lengths should have found the end. But in prellocated files, log file |
| 793 | *length is not sufficiant to find the log end. This check |
| 794 | *is must to find the end in preallocated log files. |
| 795 | */ |
| 796 | if(currentInstant < knownGoodLogEnd) |
| 797 | { |
| 798 | fuzzyLogEnd = true ; |
| 799 | return null; |
| 800 | } |
| 801 | |
| 802 | // sanity check it |
| 803 | if (SanityManager.DEBUG) |
| 804 | { |
| 805 | if (LogCounter.getLogFileNumber(currentInstant) != |
| 806 | currentLogFileNumber || |
| 807 | LogCounter.getLogFilePosition(currentInstant) != |
| 808 | recordStartPosition) |
| 809 | SanityManager.THROWASSERT( |
| 810 | "Wrong LogInstant on log record " + |
| 811 | LogCounter.toDebugString(currentInstant) + |
| 812 | " version real position (" + |
| 813 | currentLogFileNumber + "," + |
| 814 | recordStartPosition + ")"); |
| 815 | } |
| 816 | |
| 817 | |
| 818 | // if stopAt == INVALID_LOG_INSTANT, no stop instant, read till |
| 819 | // nothing more can be read. Else check scan limit |
| 820 | if (stopAt != LogCounter.INVALID_LOG_INSTANT && currentInstant > stopAt) |
| 821 | { |
| 822 | currentInstant = LogCounter.INVALID_LOG_INSTANT; |
| 823 | return null; // we went past the stopAt |
| 824 | } |
| 825 | |
| 826 | // read in the log record |
| 827 | byte[] data = input.getData(); |
| 828 | |
| 829 | if (data.length < recordLength) |
| 830 | { |
| 831 | // make a new array of sufficient size and reset the arrary |
| 832 | // in the input stream |
| 833 | data = new byte[recordLength]; |
| 834 | input.setData(data); |
| 835 | } |
| 836 | |
| 837 | // If the log is encrypted, we must do the filtering after |
| 838 | // reading and decryptiong the record. |
| 839 | |
| 840 | if (logFactory.databaseEncrypted()) |
| 841 | { |
| 842 | scan.readFully(data, 0, recordLength); |
| 843 | int len = logFactory.decrypt(data, 0, recordLength, data, 0); |
| 844 | if (SanityManager.DEBUG) |
| 845 | SanityManager.ASSERT(len == recordLength); |
| 846 | |
| 847 | input.setLimit(0, len); |
| 848 | } |
| 849 | else // no need to decrypt, only get the group and tid if we filter |
| 850 | { |
| 851 | if (groupmask == 0 && tranId == null) |
| 852 | { |
| 853 | // no filter, get the whole thing |
| 854 | scan.readFully(data, 0, recordLength); |
| 855 | input.setLimit(0, recordLength); |
| 856 | } |
| 857 | else |
| 858 | { |
| 859 | // Read only enough so that group and the tran id is in |
| 860 | // the data buffer. Group is stored as compressed int |
| 861 | // and tran id is stored as who knows what. read min |
| 862 | // of peekAmount or recordLength |
| 863 | readAmount = (recordLength > peekAmount) ? |
| 864 | peekAmount : recordLength; |
| 865 | |
| 866 | // in the data buffer, we now have enough to peek |
| 867 | scan.readFully(data, 0, readAmount); |
| 868 | input.setLimit(0, readAmount); |
| 869 | } |
| 870 | } |
| 871 | |
| 872 | lr = (LogRecord) input.readObject(); |
| 873 | if (groupmask != 0 || tranId != null) |
| 874 | { |
| 875 | if (groupmask != 0 && (groupmask & lr.group()) == 0) |
| 876 | candidate = false; // no match, throw this log record out |
| 877 | |
| 878 | if (candidate && tranId != null) |
| 879 | { |
| 880 | TransactionId tid = lr.getTransactionId(); |
| 881 | if (!tid.equals(tranId)) // nomatch |
| 882 | candidate = false; // throw this log record out |
| 883 | } |
| 884 | |
| 885 | // if this log record is not filtered out, we need to read |
| 886 | // in the rest of the log record to the input buffer. |
| 887 | // Except if it is an encrypted database, in which case the |
| 888 | // entire log record have already be read in for |
| 889 | // decryption. |
| 890 | if (candidate && !logFactory.databaseEncrypted()) |
| 891 | { |
| 892 | // read the rest of the log into the buffer |
| 893 | if (SanityManager.DEBUG) |
| 894 | SanityManager.ASSERT(readAmount > 0); |
| 895 | |
| 896 | if (readAmount < recordLength) |
| 897 | { |
| 898 | // Need to remember where we are because the log |
| 899 | // record may have read part of it off the input |
| 900 | // stream already and that position is lost when we |
| 901 | // set limit again. |
| 902 | int inputPosition = input.getPosition(); |
| 903 | |
| 904 | scan.readFully(data, readAmount, |
| 905 | recordLength-readAmount); |
| 906 | |
| 907 | input.setLimit(0, recordLength); |
| 908 | input.setPosition(inputPosition); |
| 909 | } |
| 910 | } |
| 911 | } |
| 912 | |
| 913 | /*check if the logrecord length written before and after the |
| 914 | *log record are equal, if not the end of of the log is reached. |
| 915 | *This can happen if system crashed before writing the length field |
| 916 | *in the end of the records completely. If the length is partially |
| 917 | *written or not written at all it will not match with length written |
| 918 | *in the beginning of the log record. Currentlt preallocated files |
| 919 | *are filled with zeros, log record length can never be zero; |
| 920 | *if the lengths are not matching, end of the properly written log |
| 921 | *is reached. |
| 922 | *Note: In case of Non-preallocated files earlier fuzzy case check with log |
| 923 | * file lengths should have found the end. But in prellocated files, log file |
| 924 | *length is not sufficiant to find the log end. This check |
| 925 | *is must to find the end in preallocated log files. |
| 926 | */ |
| 927 | // read the length after the log record and check it against the |
| 928 | // length before the log record, make sure we go to the correct |
| 929 | // place for skipped log record. |
| 930 | if (!candidate) |
| 931 | scan.seek(recordStartPosition - 4); |
| 932 | int checkLength = scan.readInt(); |
| 933 | if (checkLength != recordLength && checkLength < recordLength) |
| 934 | { |
| 935 | |
| 936 | |
| 937 | //lengh written in the end of the log record should be always |
| 938 | //less then the length written in the beginning if the log |
| 939 | //record was half written before the crash. |
| 940 | if(checkLength < recordLength) |
| 941 | { |
| 942 | fuzzyLogEnd = true ; |
| 943 | return null; |
| 944 | }else |
| 945 | { |
| 946 | |
| 947 | //If checklength > recordLength then it can be not be a partial write |
| 948 | //probablly it is corrupted for some reason , this should never |
| 949 | //happen throw error in debug mode. In non debug case , let's |
| 950 | //hope it's only is wrong and system can proceed. |
| 951 | |
| 952 | if (SanityManager.DEBUG) |
| 953 | { |
| 954 | throw logFactory.markCorrupt |
| 955 | (StandardException.newException( |
| 956 | SQLState.LOG_RECORD_CORRUPTED, |
| 957 | new Long(checkLength), |
| 958 | new Long(recordLength), |
| 959 | new Long(currentInstant), |
| 960 | new Long(currentLogFileNumber))); |
| 961 | |
| 962 | } |
| 963 | |
| 964 | //In non debug case, do nothing , let's hope it's only |
| 965 | //length part that is incorrect and system can proceed. |
| 966 | } |
| 967 | |
| 968 | } |
| 969 | |
| 970 | // next record start position is right after this record |
| 971 | recordStartPosition += recordLength + LogToFile.LOG_RECORD_OVERHEAD; |
| 972 | knownGoodLogEnd = LogCounter.makeLogInstantAsLong |
| 973 | (currentLogFileNumber, recordStartPosition); |
| 974 | |
| 975 | |
| 976 | if (SanityManager.DEBUG) |
| 977 | { |
| 978 | if (recordStartPosition != scan.getFilePointer()) |
| 979 | SanityManager.THROWASSERT( |
| 980 | "calculated end " + recordStartPosition + |
| 981 | " != real end " + scan.getFilePointer()); |
| 982 | } |
| 983 | else |
| 984 | { |
| 985 | // seek to the start of the next log record |
| 986 | scan.seek(recordStartPosition); |
| 987 | } |
| 988 | |
| 989 | // the scan is now positioned just past this log record and right |
| 990 | // at the beginning of the next log record |
| 991 | |
| 992 | |
| 993 | /** if the current log record is a checksum log record then |
| 994 | * using the information available in this record validate |
| 995 | * that data in the log file by matching the checksum in |
| 996 | * checksum log record and by recalculating the checksum for the |
| 997 | * specified length of the data in the log file. cheksum values |
| 998 | * should match unless the right was incomplete before the crash. |
| 999 | */ |
| 1000 | if(lr.isChecksum()) |
| 1001 | { |
| 1002 | // checksum log record should not be returned to the logger recovery redo |
| 1003 | // routines, it is just used to identify the incomplete log writes. |
| 1004 | |
| 1005 | candidate = false; |
| 1006 | Loggable op = lr.getLoggable(); |
| 1007 | if (SanityManager.DEBUG) |
| 1008 | { |
| 1009 | if (SanityManager.DEBUG_ON(LogToFile.DUMP_LOG_ONLY) || |
| 1010 | SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 1011 | |
| 1012 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 1013 | "scanned " + "Null" + " : " + op + |
| 1014 | " instant = " + |
| 1015 | LogCounter.toDebugString(currentInstant) + |
| 1016 | " logEnd = " + LogCounter.toDebugString(knownGoodLogEnd)); |
| 1017 | } |
| 1018 | |
| 1019 | ChecksumOperation clop = (ChecksumOperation) op; |
| 1020 | int ckDataLength = clop.getDataLength(); |
| 1021 | // resize the buffer to be size of checksum data length if required. |
| 1022 | if (data.length < ckDataLength) |
| 1023 | { |
| 1024 | // make a new array of sufficient size and reset the arrary |
| 1025 | // in the input stream |
| 1026 | data = new byte[ckDataLength]; |
| 1027 | input.setData(data); |
| 1028 | input.setLimit(0, ckDataLength); |
| 1029 | } |
| 1030 | |
| 1031 | boolean validChecksum = false; |
| 1032 | // check if the expected number of bytes by the checksum log |
| 1033 | // record actually exist in the file and then verify if checksum |
| 1034 | // is valid to identify any incomplete out of order writes. |
| 1035 | if((recordStartPosition + ckDataLength) <= currentLogFileLength) |
| 1036 | { |
| 1037 | // read the data into the buffer |
| 1038 | scan.readFully(data, 0, ckDataLength); |
| 1039 | // verify the checksum |
| 1040 | if(clop.isChecksumValid(data, 0 , ckDataLength)) |
| 1041 | validChecksum = true; |
| 1042 | } |
| 1043 | |
| 1044 | |
| 1045 | if(!validChecksum) |
| 1046 | { |
| 1047 | // declare that the end of the transaction log is fuzzy, checksum is invalid |
| 1048 | // only when the writes are incomplete; this can happen |
| 1049 | // only when writes at the end of the log were partially |
| 1050 | // written before the crash. |
| 1051 | |
| 1052 | if (SanityManager.DEBUG) |
| 1053 | { |
| 1054 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 1055 | { |
| 1056 | SanityManager.DEBUG( |
| 1057 | LogToFile.DBG_FLAG, |
| 1058 | "detected fuzzy log end on log file while doing checksum checks " + |
| 1059 | currentLogFileNumber + |
| 1060 | " checksum record start position " + recordStartPosition + |
| 1061 | " file length " + currentLogFileLength + |
| 1062 | " checksumDataLength=" + ckDataLength); |
| 1063 | } |
| 1064 | |
| 1065 | } |
| 1066 | |
| 1067 | fuzzyLogEnd = true; |
| 1068 | scan.close(); |
| 1069 | scan = null; |
| 1070 | return null; |
| 1071 | } |
| 1072 | |
| 1073 | // reset the scan to the start of the next log record |
| 1074 | scan.seek(recordStartPosition); |
| 1075 | } |
| 1076 | |
| 1077 | |
| 1078 | } while (candidate == false) ; |
| 1079 | |
| 1080 | return lr; |
| 1081 | } |
| 1082 | |
| 1083 | |
| 1084 | /** |
| 1085 | Reset the scan to the given LogInstant. |
| 1086 | |
| 1087 | @param instant the position to reset to |
| 1088 | @exception IOException scan cannot access the log at the new position. |
| 1089 | @exception StandardException cloudscape standard error policy |
| 1090 | */ |
| 1091 | |
| 1092 | public void resetPosition(LogInstant instant) |
| 1093 | throws IOException, StandardException |
| 1094 | { |
| 1095 | if (SanityManager.DEBUG) |
| 1096 | SanityManager.ASSERT(instant != null); |
| 1097 | |
| 1098 | long instant_long = ((LogCounter)instant).getValueAsLong(); |
| 1099 | |
| 1100 | if ((instant_long == LogCounter.INVALID_LOG_INSTANT) || |
| 1101 | (stopAt != LogCounter.INVALID_LOG_INSTANT && |
| 1102 | (scanDirection == FORWARD && instant_long > stopAt) || |
| 1103 | (scanDirection == FORWARD && instant_long < stopAt))) |
| 1104 | { |
| 1105 | close(); |
| 1106 | |
| 1107 | throw StandardException.newException( |
| 1108 | SQLState.LOG_RESET_BEYOND_SCAN_LIMIT, |
| 1109 | instant, new LogCounter(stopAt)); |
| 1110 | } |
| 1111 | else |
| 1112 | { |
| 1113 | long fnum = ((LogCounter)instant).getLogFileNumber(); |
| 1114 | |
| 1115 | if (fnum != currentLogFileNumber) |
| 1116 | { |
| 1117 | if (SanityManager.DEBUG) |
| 1118 | { |
| 1119 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 1120 | { |
| 1121 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 1122 | "Scan " + scanDirection + |
| 1123 | " resetting to " + instant + |
| 1124 | " need to switch log from " + |
| 1125 | currentLogFileNumber + " to " + fnum); |
| 1126 | } |
| 1127 | } |
| 1128 | |
| 1129 | scan.close(); |
| 1130 | scan = logFactory.getLogFileAtPosition(instant_long); |
| 1131 | |
| 1132 | currentLogFileNumber= fnum; |
| 1133 | |
| 1134 | if (scanDirection == FORWARD) |
| 1135 | { |
| 1136 | // NOTE: |
| 1137 | // |
| 1138 | // just get the length of the file without syncing. |
| 1139 | // this only works because the only place forward scan is used |
| 1140 | // right now is on recovery redo and nothing is being added to |
| 1141 | // the current log file. When the forward scan is used for some |
| 1142 | // other purpose, need to sync access to the end of the log |
| 1143 | // |
| 1144 | currentLogFileLength = scan.length(); |
| 1145 | } |
| 1146 | } |
| 1147 | else |
| 1148 | |
| 1149 | { |
| 1150 | long fpos = ((LogCounter)instant).getLogFilePosition(); |
| 1151 | scan.seek(fpos); |
| 1152 | |
| 1153 | // |
| 1154 | //RESOLVE: Can this be optimized? Does it belong here. |
| 1155 | currentLogFileLength = scan.length(); |
| 1156 | |
| 1157 | if (SanityManager.DEBUG) |
| 1158 | { |
| 1159 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 1160 | { |
| 1161 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 1162 | "Scan reset to " + instant); |
| 1163 | } |
| 1164 | } |
| 1165 | } |
| 1166 | |
| 1167 | |
| 1168 | currentInstant = instant_long; |
| 1169 | |
| 1170 | //scan is being reset, it is possibly that, scan is doing a random |
| 1171 | //access of the log file. set the knownGoodLogEnd to the instant |
| 1172 | //scan is being reset to. |
| 1173 | //Note: reset gets called with undo forward scan for CLR processing during |
| 1174 | //recovery, if this value is not reset checks to find the end of log |
| 1175 | //getNextRecordForward() will fail because undoscan scans log file |
| 1176 | //back & forth to redo CLR's. |
| 1177 | knownGoodLogEnd = currentInstant; |
| 1178 | |
| 1179 | if (SanityManager.DEBUG) |
| 1180 | { |
| 1181 | if (SanityManager.DEBUG_ON(LogToFile.DBG_FLAG)) |
| 1182 | { |
| 1183 | SanityManager.DEBUG(LogToFile.DBG_FLAG, |
| 1184 | "Scan.getInstant reset to " + currentInstant + |
| 1185 | LogCounter.toDebugString(currentInstant)); |
| 1186 | } |
| 1187 | } |
| 1188 | } |
| 1189 | } |
| 1190 | |
| 1191 | /** |
| 1192 | Return the log instant (as an integer) the scan is currently on - this is the log |
| 1193 | instant of the log record that was returned by getNextRecord. |
| 1194 | */ |
| 1195 | public long getInstant() |
| 1196 | { |
| 1197 | return currentInstant; |
| 1198 | } |
| 1199 | |
| 1200 | /** |
| 1201 | Return the log instant at the end of the log record on the current |
| 1202 | LogFile in the form of a log instant. |
| 1203 | After the scan has been closed, the end of the last log record will be |
| 1204 | returned except when the scan ended in an empty log file. In that |
| 1205 | case, the start of this empty log file will be returned. (This is |
| 1206 | done to make sure new log records are inserted into the newest log |
| 1207 | file.) |
| 1208 | */ |
| 1209 | public long getLogRecordEnd() |
| 1210 | { |
| 1211 | return knownGoodLogEnd; |
| 1212 | } |
| 1213 | |
| 1214 | /** |
| 1215 | returns true if there is partially writen log records before the crash |
| 1216 | in the last log file. Partiall wrires are identified during forward |
| 1217 | redo scans for log recovery. |
| 1218 | */ |
| 1219 | public boolean isLogEndFuzzy() |
| 1220 | { |
| 1221 | return fuzzyLogEnd; |
| 1222 | } |
| 1223 | |
| 1224 | /** |
| 1225 | Return the log instant the scan is currently on - this is the log |
| 1226 | instant of the log record that was returned by getNextRecord. |
| 1227 | */ |
| 1228 | public LogInstant getLogInstant() |
| 1229 | { |
| 1230 | if (currentInstant == LogCounter.INVALID_LOG_INSTANT) |
| 1231 | return null; |
| 1232 | else |
| 1233 | return new LogCounter(currentInstant); |
| 1234 | } |
| 1235 | |
| 1236 | /** |
| 1237 | Close the scan. |
| 1238 | */ |
| 1239 | public void close() |
| 1240 | { |
| 1241 | if (scan != null) |
| 1242 | { |
| 1243 | try |
| 1244 | { |
| 1245 | scan.close(); |
| 1246 | } |
| 1247 | catch (IOException ioe) |
| 1248 | {} |
| 1249 | |
| 1250 | scan = null; |
| 1251 | } |
| 1252 | |
| 1253 | logFactory = null; |
| 1254 | currentLogFileNumber = -1; |
| 1255 | currentLogFileLength = -1; |
| 1256 | // Do not reset knownGoodLogEnd, it needs to be available after the |
| 1257 | // scan has closed. |
| 1258 | currentInstant = LogCounter.INVALID_LOG_INSTANT; |
| 1259 | stopAt = LogCounter.INVALID_LOG_INSTANT; |
| 1260 | scanDirection = 0; |
| 1261 | } |
| 1262 | |
| 1263 | } |