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Overview
Comment: | When attempting to restart a wal file, make any required calls to sqlite3_randomness() before waiting on or checking for wal file readers. This restores the behaviour exhibited by the trunk. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | checkpoint-truncate |
Files: | files | file ages | folders |
SHA1: |
6ee08769f0ffbb3d620c66b89180ece7 |
User & Date: | dan 2014-12-02 19:35:09.278 |
Context
2014-12-02
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20:51 | Add support for SQLITE_CHECKPOINT_TRUNCATE. (check-in: edda2b9e7a user: drh tags: trunk) | |
19:35 | When attempting to restart a wal file, make any required calls to sqlite3_randomness() before waiting on or checking for wal file readers. This restores the behaviour exhibited by the trunk. (Closed-Leaf check-in: 6ee08769f0 user: dan tags: checkpoint-truncate) | |
19:04 | Add the SQLITE_CHECKPOINT_TRUNCATE option. (check-in: 8e20a43419 user: dan tags: checkpoint-truncate) | |
Changes
Changes to src/wal.c.
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1631 1632 1633 1634 1635 1636 1637 1638 | ** c) any existing readers are reading exclusively from the database ** file - there are no readers that may attempt to read a frame from ** the log file. ** ** This function updates the shared-memory structures so that the next ** client to write to the database (which may be this one) does so by ** writing frames into the start of the log file. */ | > > > > | | | 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 | ** c) any existing readers are reading exclusively from the database ** file - there are no readers that may attempt to read a frame from ** the log file. ** ** This function updates the shared-memory structures so that the next ** client to write to the database (which may be this one) does so by ** writing frames into the start of the log file. ** ** The value of parameter salt1 is used as the aSalt[1] value in the ** new wal-index header. It should be passed a pseudo-random value (i.e. ** one obtained from sqlite3_randomness()). */ static void walRestartHdr(Wal *pWal, u32 salt1){ volatile WalCkptInfo *pInfo = walCkptInfo(pWal); int i; /* Loop counter */ u32 *aSalt = pWal->hdr.aSalt; /* Big-endian salt values */ pWal->nCkpt++; pWal->hdr.mxFrame = 0; sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0])); memcpy(&pWal->hdr.aSalt[1], &salt1, 4); walIndexWriteHdr(pWal); pInfo->nBackfill = 0; pInfo->aReadMark[1] = 0; for(i=2; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED; assert( pInfo->aReadMark[0]==0 ); } |
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1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 | ** the next process to write to the database restarts the wal file. */ if( rc==SQLITE_OK && eMode!=SQLITE_CHECKPOINT_PASSIVE ){ assert( pWal->writeLock ); if( pInfo->nBackfill<pWal->hdr.mxFrame ){ rc = SQLITE_BUSY; }else if( eMode>=SQLITE_CHECKPOINT_RESTART ){ assert( mxSafeFrame==pWal->hdr.mxFrame ); rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(1), WAL_NREADER-1); if( rc==SQLITE_OK ){ if( eMode==SQLITE_CHECKPOINT_TRUNCATE ){ /* If this is a TRUNCATE checkpoint, also truncate the wal file ** to zero bytes in size on disk. ** ** In theory, it might be safe to do this without updating the ** wal-index header in shared memory, as all subsequent reader or ** writer clients should see that the entire log file has been ** checkpointed and behave accordingly. This seems unsafe though, ** as it would leave the system in a state where the contents of ** the wal-index header do not match the contents of the ** file-system. To avoid this, update the wal-index header to ** indicate that the log file contains zero valid frames. */ | > > | | 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 | ** the next process to write to the database restarts the wal file. */ if( rc==SQLITE_OK && eMode!=SQLITE_CHECKPOINT_PASSIVE ){ assert( pWal->writeLock ); if( pInfo->nBackfill<pWal->hdr.mxFrame ){ rc = SQLITE_BUSY; }else if( eMode>=SQLITE_CHECKPOINT_RESTART ){ u32 salt1; sqlite3_randomness(4, &salt1); assert( mxSafeFrame==pWal->hdr.mxFrame ); rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(1), WAL_NREADER-1); if( rc==SQLITE_OK ){ if( eMode==SQLITE_CHECKPOINT_TRUNCATE ){ /* If this is a TRUNCATE checkpoint, also truncate the wal file ** to zero bytes in size on disk. ** ** In theory, it might be safe to do this without updating the ** wal-index header in shared memory, as all subsequent reader or ** writer clients should see that the entire log file has been ** checkpointed and behave accordingly. This seems unsafe though, ** as it would leave the system in a state where the contents of ** the wal-index header do not match the contents of the ** file-system. To avoid this, update the wal-index header to ** indicate that the log file contains zero valid frames. */ walRestartHdr(pWal, salt1); rc = sqlite3OsTruncate(pWal->pWalFd, 0); } walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1); } } } |
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2645 2646 2647 2648 2649 2650 2651 | ** frames will overwrite the start of the existing log. Update the ** wal-index header to reflect this. ** ** In theory it would be Ok to update the cache of the header only ** at this point. But updating the actual wal-index header is also ** safe and means there is no special case for sqlite3WalUndo() ** to handle if this transaction is rolled back. */ | | | 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 | ** frames will overwrite the start of the existing log. Update the ** wal-index header to reflect this. ** ** In theory it would be Ok to update the cache of the header only ** at this point. But updating the actual wal-index header is also ** safe and means there is no special case for sqlite3WalUndo() ** to handle if this transaction is rolled back. */ walRestartHdr(pWal, salt1); walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1); }else if( rc!=SQLITE_BUSY ){ return rc; } } walUnlockShared(pWal, WAL_READ_LOCK(0)); pWal->readLock = -1; |
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