diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/pager.c | 56 |
1 files changed, 39 insertions, 17 deletions
diff --git a/src/pager.c b/src/pager.c index 335ec21e5..e17bcf5bd 100644 --- a/src/pager.c +++ b/src/pager.c @@ -18,7 +18,7 @@ ** file simultaneously, or one process from reading the database while ** another is writing. ** -** @(#) $Id: pager.c,v 1.572 2009/03/23 04:33:33 danielk1977 Exp $ +** @(#) $Id: pager.c,v 1.573 2009/03/26 17:13:06 danielk1977 Exp $ */ #ifndef SQLITE_OMIT_DISKIO #include "sqliteInt.h" @@ -3329,11 +3329,12 @@ int sqlite3PagerOpen( ** PAGER_SHARED state. It tests if there is a hot journal present in ** the file-system for the given pager. A hot journal is one that ** needs to be played back. According to this function, a hot-journal -** file exists if the following three criteria are met: +** file exists if the following criteria are met: ** ** * The journal file exists in the file system, and ** * No process holds a RESERVED or greater lock on the database file, and -** * The database file itself is greater than 0 bytes in size. +** * The database file itself is greater than 0 bytes in size, and +** * The first byte of the journal file exists and is not 0x00. ** ** If the current size of the database file is 0 but a journal file ** exists, that is probably an old journal left over from a prior @@ -3341,14 +3342,12 @@ int sqlite3PagerOpen( ** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK ** is returned. ** -** This routine does not open the journal file to examine its -** content. Hence, the journal might contain the name of a master -** journal file that has been deleted, and hence not be hot. Or -** the header of the journal might be zeroed out. This routine -** does not discover these cases of a non-hot journal - if the -** journal file exists and is not empty this routine assumes it -** is hot. The pager_playback() routine will discover that the -** journal file is not really hot and will no-op. +** This routine does not check if there is a master journal filename +** at the end of the file. If there is, and that master journal file +** does not exist, then the journal file is not really hot. In this +** case this routine will return a false-positive. The pager_playback() +** routine will discover that the journal file is not really hot and +** will not roll it back. ** ** If a hot-journal file is found to exist, *pExists is set to 1 and ** SQLITE_OK returned. If no hot-journal file is present, *pExists is @@ -3359,29 +3358,52 @@ int sqlite3PagerOpen( static int hasHotJournal(Pager *pPager, int *pExists){ sqlite3_vfs * const pVfs = pPager->pVfs; int rc; /* Return code */ - int exists = 0; /* True if a journal file is present */ - int locked = 0; /* True if some process holds a RESERVED lock */ + int exists; /* True if a journal file is present */ assert( pPager!=0 ); assert( pPager->useJournal ); assert( isOpen(pPager->fd) ); + assert( !isOpen(pPager->jfd) ); *pExists = 0; rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists); if( rc==SQLITE_OK && exists ){ + int locked; /* True if some process holds a RESERVED lock */ rc = sqlite3OsCheckReservedLock(pPager->fd, &locked); if( rc==SQLITE_OK && !locked ){ int nPage; + + /* Check the size of the database file. If it consists of 0 pages, + ** then delete the journal file. See the header comment above for + ** the reasoning here. + */ rc = sqlite3PagerPagecount(pPager, &nPage); if( rc==SQLITE_OK ){ - if( nPage==0 ){ - sqlite3OsDelete(pVfs, pPager->zJournal, 0); + if( nPage==0 ){ + rc = sqlite3OsDelete(pVfs, pPager->zJournal, 0); }else{ - *pExists = 1; + /* The journal file exists and no other connection has a reserved + ** or greater lock on the database file. Now check that there is + ** at least one non-zero bytes at the start of the journal file. + ** If there is, then we consider this journal to be hot. If not, + ** it can be ignored. + */ + int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL; + rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f); + if( rc==SQLITE_OK ){ + u8 first = 0; + rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0); + if( rc==SQLITE_IOERR_SHORT_READ ){ + rc = SQLITE_OK; + } + sqlite3OsClose(pPager->jfd); + *pExists = (first!=0); + } } } } } + return rc; } @@ -3927,7 +3949,7 @@ static int pager_open_journal(Pager *pPager){ sqlite3MemJournalOpen(pPager->jfd); }else{ const int flags = /* VFS flags to open journal file */ - SQLITE_OPEN_READWRITE|SQLITE_OPEN_EXCLUSIVE|SQLITE_OPEN_CREATE| + SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE| (pPager->tempFile ? (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL): (SQLITE_OPEN_MAIN_JOURNAL) |