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If you delete a database file but not its *-wal file, then open the database

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(thus creating a new empty database file) the *-wal file is automatically
deleted.

FossilOrigin-Name: 95c69dfbddaf4367cd699dfe8fcf8e06030c1f53
This commit is contained in:
drh
2010-07-01 19:45:34 +00:00
parent d0b0d4dc23
commit 32f2964390
4 changed files with 110 additions and 20 deletions
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51
src/pager.c
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@@ -2414,12 +2414,19 @@ static int pagerBeginReadTransaction(Pager *pPager){
}
/*
** Check if the *-wal file that corresponds to the database opened by pPager
** exists. Assuming no error occurs, set *pExists to 1 if the file exists,
** or 0 otherwise and return SQLITE_OK. If an IO or OOM error occurs, return
** Check for the existence of or delete the *-wal file that corresponds to
** the database opened by pPager.
**
** When pExists!=NULL, set *pExists to 1 if the *-wal file exists, or 0
** if the *-wal file does not exist.
**
** When pExists==NULL, delete the *-wal file if it exists, or the do
** nothing if the *-wal file does not exist.
**
** Return SQLITE_OK on success. If on an IO or OOM error occurs, return
** an SQLite error code.
*/
static int pagerHasWAL(Pager *pPager, int *pExists){
static int pagerCheckForOrDeleteWAL(Pager *pPager, int *pExists){
int rc; /* Return code */
char *zWal; /* Name of the WAL file */
@@ -2428,7 +2435,11 @@ static int pagerHasWAL(Pager *pPager, int *pExists){
if( !zWal ){
rc = SQLITE_NOMEM;
}else{
rc = sqlite3OsAccess(pPager->pVfs, zWal, SQLITE_ACCESS_EXISTS, pExists);
if( pExists ){
rc = sqlite3OsAccess(pPager->pVfs, zWal, SQLITE_ACCESS_EXISTS, pExists);
}else{
rc = sqlite3OsDelete(pPager->pVfs, zWal, 0);
}
sqlite3_free(zWal);
}
return rc;
@@ -2436,22 +2447,38 @@ static int pagerHasWAL(Pager *pPager, int *pExists){
/*
** Check if the *-wal file that corresponds to the database opened by pPager
** exists. If it does, open the pager in WAL mode. Otherwise, if no error
** occurs, make sure Pager.journalMode is not set to PAGER_JOURNALMODE_WAL.
** If an IO or OOM error occurs, return an SQLite error code.
** exists if the database is not empy, or verify that the *-wal file does
** not exist (by deleting it) if the database file is empty.
**
** If the database is not empty and the *-wal file exists, open the pager
** in WAL mode. If the database is empty or if no *-wal file exists and
** if no error occurs, make sure Pager.journalMode is not set to
** PAGER_JOURNALMODE_WAL.
**
** Return SQLITE_OK or an error code.
**
** If the WAL file is opened, also open a snapshot (read transaction).
**
** The caller must hold a SHARED lock on the database file to call this
** function. Because an EXCLUSIVE lock on the db file is required to delete
** a WAL, this ensures there is no race condition between the xAccess()
** below and an xDelete() being executed by some other connection.
** a WAL on a none-empty database, this ensures there is no race condition
** between the xAccess() below and an xDelete() being executed by some
** other connection.
*/
static int pagerOpenWalIfPresent(Pager *pPager){
int rc = SQLITE_OK;
if( !pPager->tempFile ){
int isWal; /* True if WAL file exists */
rc = pagerHasWAL(pPager, &isWal);
int nPage; /* Size of the database file */
assert( pPager->state>=SHARED_LOCK );
rc = sqlite3PagerPagecount(pPager, &nPage);
if( rc ) return rc;
if( nPage==0 ){
rc = pagerCheckForOrDeleteWAL(pPager, 0);
isWal = 0;
}else{
rc = pagerCheckForOrDeleteWAL(pPager, &isWal);
}
if( rc==SQLITE_OK ){
if( isWal ){
pager_reset(pPager);
@@ -6071,7 +6098,7 @@ int sqlite3PagerCloseWal(Pager *pPager){
int logexists = 0;
rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_SHARED);
if( rc==SQLITE_OK ){
rc = pagerHasWAL(pPager, &logexists);
rc = pagerCheckForOrDeleteWAL(pPager, &logexists);
}
if( rc==SQLITE_OK && logexists ){
rc = sqlite3WalOpen(pPager->pVfs, pPager->fd,