DBD-SQLite
view release on metacpan or search on metacpan
As of 1.49_05, you can also make a database read-only by setting
"ReadOnly" attribute to true (only) when you connect to a
database. Actually you can set it after you connect, but in that
case, it can't make the database read-only, and you'll see a
warning (which you can hide by turning "PrintWarn" off).
DBD::SQLite And File::Temp
When you use File::Temp to create a temporary file/directory for
SQLite databases, you need to remember:
tempfile may be locked exclusively
You may want to use "tempfile()" to create a temporary
database filename for DBD::SQLite, but as noted in
File::Temp's POD, this file may have an exclusive lock under
some operating systems (notably Mac OSX), and result in a
"database is locked" error. To avoid this, set EXLOCK option
to false when you call tempfile().
($fh, $filename) = tempfile($template, EXLOCK => 0);
CLEANUP may not work unless a database is disconnected
When you set CLEANUP option to true when you create a
temporary directory with "tempdir()" or "newdir()", you may
have to disconnect databases explicitly before the temporary
directory is gone (notably under MS Windows).
lib/DBD/SQLite.pm view on Meta::CPAN
can't make the database read-only, and you'll see a warning (which
you can hide by turning C<PrintWarn> off).
=head2 DBD::SQLite And File::Temp
When you use L<File::Temp> to create a temporary file/directory for
SQLite databases, you need to remember:
=over 4
=item tempfile may be locked exclusively
You may want to use C<tempfile()> to create a temporary database
filename for DBD::SQLite, but as noted in L<File::Temp>'s POD,
this file may have an exclusive lock under some operating systems
(notably Mac OSX), and result in a "database is locked" error.
To avoid this, set EXLOCK option to false when you call tempfile().
($fh, $filename) = tempfile($template, EXLOCK => 0);
=item CLEANUP may not work unless a database is disconnected
When you set CLEANUP option to true when you create a temporary
directory with C<tempdir()> or C<newdir()>, you may have to
disconnect databases explicitly before the temporary directory
is gone (notably under MS Windows).
** New error codes may be added in future versions of SQLite.
**
** See also: [extended result code definitions]
*/
#define SQLITE_OK 0 /* Successful result */
/* beginning-of-error-codes */
#define SQLITE_ERROR 1 /* Generic error */
#define SQLITE_INTERNAL 2 /* Internal logic error in SQLite */
#define SQLITE_PERM 3 /* Access permission denied */
#define SQLITE_ABORT 4 /* Callback routine requested an abort */
#define SQLITE_BUSY 5 /* The database file is locked */
#define SQLITE_LOCKED 6 /* A table in the database is locked */
#define SQLITE_NOMEM 7 /* A malloc() failed */
#define SQLITE_READONLY 8 /* Attempt to write a readonly database */
#define SQLITE_INTERRUPT 9 /* Operation terminated by sqlite3_interrupt()*/
#define SQLITE_IOERR 10 /* Some kind of disk I/O error occurred */
#define SQLITE_CORRUPT 11 /* The database disk image is malformed */
#define SQLITE_NOTFOUND 12 /* Unknown opcode in sqlite3_file_control() */
#define SQLITE_FULL 13 /* Insertion failed because database is full */
#define SQLITE_CANTOPEN 14 /* Unable to open the database file */
#define SQLITE_PROTOCOL 15 /* Database lock protocol error */
#define SQLITE_EMPTY 16 /* Internal use only */
** this file-control is NULL. However, if the database file is being synced
** as part of a multi-database commit, the argument points to a nul-terminated
** string containing the transactions super-journal file name. VFSes that
** do not need this signal should silently ignore this opcode. Applications
** should not call [sqlite3_file_control()] with this opcode as doing so may
** disrupt the operation of the specialized VFSes that do require it.
**
** <li>[[SQLITE_FCNTL_COMMIT_PHASETWO]]
** The [SQLITE_FCNTL_COMMIT_PHASETWO] opcode is generated internally by SQLite
** and sent to the VFS after a transaction has been committed immediately
** but before the database is unlocked. VFSes that do not need this signal
** should silently ignore this opcode. Applications should not call
** [sqlite3_file_control()] with this opcode as doing so may disrupt the
** operation of the specialized VFSes that do require it.
**
** <li>[[SQLITE_FCNTL_WIN32_AV_RETRY]]
** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
** retry counts and intervals for certain disk I/O operations for the
** windows [VFS] in order to provide robustness in the presence of
** anti-virus programs. By default, the windows VFS will retry file read,
** file write, and file delete operations up to 10 times, with a delay
** <ul>
** <li> SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
** <li> SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
** <li> SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
** <li> SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
** </ul>
**
** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
** was given on the corresponding lock.
**
** The xShmLock method can transition between unlocked and SHARED or
** between unlocked and EXCLUSIVE. It cannot transition between SHARED
** and EXCLUSIVE.
*/
#define SQLITE_SHM_UNLOCK 1
#define SQLITE_SHM_LOCK 2
#define SQLITE_SHM_SHARED 4
#define SQLITE_SHM_EXCLUSIVE 8
/*
** CAPI3REF: Maximum xShmLock index
**
/*
** CAPI3REF: Register A Callback To Handle SQLITE_BUSY Errors
** KEYWORDS: {busy-handler callback} {busy handler}
** METHOD: sqlite3
**
** ^The sqlite3_busy_handler(D,X,P) routine sets a callback function X
** that might be invoked with argument P whenever
** an attempt is made to access a database table associated with
** [database connection] D when another thread
** or process has the table locked.
** The sqlite3_busy_handler() interface is used to implement
** [sqlite3_busy_timeout()] and [PRAGMA busy_timeout].
**
** ^If the busy callback is NULL, then [SQLITE_BUSY]
** is returned immediately upon encountering the lock. ^If the busy callback
** is not NULL, then the callback might be invoked with two arguments.
**
** ^The first argument to the busy handler is a copy of the void* pointer which
** is the third argument to sqlite3_busy_handler(). ^The second argument to
** the busy handler callback is the number of times that the busy handler has
**
** The presence of a busy handler does not guarantee that it will be invoked
** when there is lock contention. ^If SQLite determines that invoking the busy
** handler could result in a deadlock, it will go ahead and return [SQLITE_BUSY]
** to the application instead of invoking the
** busy handler.
** Consider a scenario where one process is holding a read lock that
** it is trying to promote to a reserved lock and
** a second process is holding a reserved lock that it is trying
** to promote to an exclusive lock. The first process cannot proceed
** because it is blocked by the second and the second process cannot
** proceed because it is blocked by the first. If both processes
** invoke the busy handlers, neither will make any progress. Therefore,
** SQLite returns [SQLITE_BUSY] for the first process, hoping that this
** will induce the first process to release its read lock and allow
** the second process to proceed.
**
** ^The default busy callback is NULL.
**
** ^(There can only be a single busy handler defined for each
** [database connection]. Setting a new busy handler clears any
** previously set handler.)^ ^Note that calling [sqlite3_busy_timeout()]
** A busy handler must not close the database connection
** or [prepared statement] that invoked the busy handler.
*/
SQLITE_API int sqlite3_busy_handler(sqlite3*,int(*)(void*,int),void*);
/*
** CAPI3REF: Set A Busy Timeout
** METHOD: sqlite3
**
** ^This routine sets a [sqlite3_busy_handler | busy handler] that sleeps
** for a specified amount of time when a table is locked. ^The handler
** will sleep multiple times until at least "ms" milliseconds of sleeping
** have accumulated. ^After at least "ms" milliseconds of sleeping,
** the handler returns 0 which causes [sqlite3_step()] to return
** [SQLITE_BUSY].
**
** ^Calling this routine with an argument less than or equal to zero
** turns off all busy handlers.
**
** ^(There can only be a single busy handler for a particular
** [database connection] at any given moment. If another busy handler
** CAPI3REF: Online Backup API.
**
** The backup API copies the content of one database into another.
** It is useful either for creating backups of databases or
** for copying in-memory databases to or from persistent files.
**
** See Also: [Using the SQLite Online Backup API]
**
** ^SQLite holds a write transaction open on the destination database file
** for the duration of the backup operation.
** ^The source database is read-locked only while it is being read;
** it is not locked continuously for the entire backup operation.
** ^Thus, the backup may be performed on a live source database without
** preventing other database connections from
** reading or writing to the source database while the backup is underway.
**
** ^(To perform a backup operation:
** <ol>
** <li><b>sqlite3_backup_init()</b> is called once to initialize the
** backup,
** <li><b>sqlite3_backup_step()</b> is called one or more times to transfer
** the data between the two databases, and finally
** errors are considered fatal.)^ The application must accept
** that the backup operation has failed and pass the backup operation handle
** to the sqlite3_backup_finish() to release associated resources.
**
** ^The first call to sqlite3_backup_step() obtains an exclusive lock
** on the destination file. ^The exclusive lock is not released until either
** sqlite3_backup_finish() is called or the backup operation is complete
** and sqlite3_backup_step() returns [SQLITE_DONE]. ^Every call to
** sqlite3_backup_step() obtains a [shared lock] on the source database that
** lasts for the duration of the sqlite3_backup_step() call.
** ^Because the source database is not locked between calls to
** sqlite3_backup_step(), the source database may be modified mid-way
** through the backup process. ^If the source database is modified by an
** external process or via a database connection other than the one being
** used by the backup operation, then the backup will be automatically
** restarted by the next call to sqlite3_backup_step(). ^If the source
** database is modified by the using the same database connection as is used
** by the backup operation, then the backup database is automatically
** updated at the same time.
**
** [[sqlite3_backup_finish()]] <b>sqlite3_backup_finish()</b>
** ^This API may be used to register a callback that SQLite will invoke
** when the connection currently holding the required lock relinquishes it.
** ^This API is only available if the library was compiled with the
** [SQLITE_ENABLE_UNLOCK_NOTIFY] C-preprocessor symbol defined.
**
** See Also: [Using the SQLite Unlock Notification Feature].
**
** ^Shared-cache locks are released when a database connection concludes
** its current transaction, either by committing it or rolling it back.
**
** ^When a connection (known as the blocked connection) fails to obtain a
** shared-cache lock and SQLITE_LOCKED is returned to the caller, the
** identity of the database connection (the blocking connection) that
** has locked the required resource is stored internally. ^After an
** application receives an SQLITE_LOCKED error, it may call the
** sqlite3_unlock_notify() method with the blocked connection handle as
** the first argument to register for a callback that will be invoked
** when the blocking connections current transaction is concluded. ^The
** callback is invoked from within the [sqlite3_step] or [sqlite3_close]
** call that concludes the blocking connection's transaction.
**
** ^(If sqlite3_unlock_notify() is called in a multi-threaded application,
** there is a chance that the blocking connection will have already
** concluded its transaction by the time sqlite3_unlock_notify() is invoked.
** If this happens, then the specified callback is invoked immediately,
** from within the call to sqlite3_unlock_notify().)^
**
** ^If the blocked connection is attempting to obtain a write-lock on a
** shared-cache table, and more than one other connection currently holds
** a read-lock on the same table, then SQLite arbitrarily selects one of
** the other connections to use as the blocking connection.
**
** ^(There may be at most one unlock-notify callback registered by a
** blocked connection. If sqlite3_unlock_notify() is called when the
** blocked connection already has a registered unlock-notify callback,
** then the new callback replaces the old.)^ ^If sqlite3_unlock_notify() is
** called with a NULL pointer as its second argument, then any existing
** unlock-notify callback is canceled. ^The blocked connections
** unlock-notify callback may also be canceled by closing the blocked
** connection using [sqlite3_close()].
**
** The unlock-notify callback is not reentrant. If an application invokes
** any sqlite3_xxx API functions from within an unlock-notify callback, a
** crash or deadlock may be the result.
**
** ^Unless deadlock is detected (see below), sqlite3_unlock_notify() always
** returns SQLITE_OK.
**
** <b>Callback Invocation Details</b>
**
** When an unlock-notify callback is registered, the application provides a
** single void* pointer that is passed to the callback when it is invoked.
** However, the signature of the callback function allows SQLite to pass
** it an array of void* context pointers. The first argument passed to
** an unlock-notify callback is a pointer to an array of void* pointers,
** and the second is the number of entries in the array.
**
** When a blocking connection's transaction is concluded, there may be
** more than one blocked connection that has registered for an unlock-notify
** callback. ^If two or more such blocked connections have specified the
** same callback function, then instead of invoking the callback function
** multiple times, it is invoked once with the set of void* context pointers
** specified by the blocked connections bundled together into an array.
** This gives the application an opportunity to prioritize any actions
** related to the set of unblocked database connections.
**
** <b>Deadlock Detection</b>
**
** Assuming that after registering for an unlock-notify callback a
** database waits for the callback to be issued before taking any further
** action (a reasonable assumption), then using this API may cause the
** application to deadlock. For example, if connection X is waiting for
** connection Y's transaction to be concluded, and similarly connection
** Y is waiting on connection X's transaction, then neither connection
** will proceed and the system may remain deadlocked indefinitely.
**
** To avoid this scenario, the sqlite3_unlock_notify() performs deadlock
** detection. ^If a given call to sqlite3_unlock_notify() would put the
** system in a deadlocked state, then SQLITE_LOCKED is returned and no
** unlock-notify callback is registered. The system is said to be in
** a deadlocked state if connection A has registered for an unlock-notify
** callback on the conclusion of connection B's transaction, and connection
** B has itself registered for an unlock-notify callback when connection
** A's transaction is concluded. ^Indirect deadlock is also detected, so
** the system is also considered to be deadlocked if connection B has
** registered for an unlock-notify callback on the conclusion of connection
** C's transaction, where connection C is waiting on connection A. ^Any
** number of levels of indirection are allowed.
**
** <b>The "DROP TABLE" Exception</b>
**
** When a call to [sqlite3_step()] returns SQLITE_LOCKED, it is almost
** always appropriate to call sqlite3_unlock_notify(). There is however,
** one exception. When executing a "DROP TABLE" or "DROP INDEX" statement,
** SQLite checks if there are any currently executing SELECT statements
** invoked immediately. If the application then re-attempts the "DROP TABLE"
** or "DROP INDEX" query, an infinite loop might be the result.
**
** One way around this problem is to check the extended error code returned
** by an sqlite3_step() call. ^(If there is a blocking connection, then the
** extended error code is set to SQLITE_LOCKED_SHAREDCACHE. Otherwise, in
** the special "DROP TABLE/INDEX" case, the extended error code is just
** SQLITE_LOCKED.)^
*/
SQLITE_API int sqlite3_unlock_notify(
sqlite3 *pBlocked, /* Waiting connection */
void (*xNotify)(void **apArg, int nArg), /* Callback function to invoke */
void *pNotifyArg /* Argument to pass to xNotify */
);
/*
** CAPI3REF: String Comparison
**
** ^The [sqlite3_stricmp()] and [sqlite3_strnicmp()] APIs allow applications
** and extensions to compare the contents of two buffers containing UTF-8
** unlock so that it can proceed.
**
** When X.pBlockingConnection==Y, that means that something that X tried
** tried to do recently failed with an SQLITE_LOCKED error due to locks
** held by Y.
*/
sqlite3 *pBlockingConnection; /* Connection that caused SQLITE_LOCKED */
sqlite3 *pUnlockConnection; /* Connection to watch for unlock */
void *pUnlockArg; /* Argument to xUnlockNotify */
void (*xUnlockNotify)(void **, int); /* Unlock notify callback */
sqlite3 *pNextBlocked; /* Next in list of all blocked connections */
#endif
#ifdef SQLITE_USER_AUTHENTICATION
sqlite3_userauth auth; /* User authentication information */
#endif
};
/*
** A macro to discover the encoding of a database.
*/
#define SCHEMA_ENC(db) ((db)->aDb[0].pSchema->enc)
#else
#define sqlite3SelectExprHeight(x) 0
#define sqlite3ExprCheckHeight(x,y)
#endif
SQLITE_PRIVATE void sqlite3ExprSetErrorOffset(Expr*,int);
SQLITE_PRIVATE u32 sqlite3Get4byte(const u8*);
SQLITE_PRIVATE void sqlite3Put4byte(u8*, u32);
#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
SQLITE_PRIVATE void sqlite3ConnectionBlocked(sqlite3 *, sqlite3 *);
SQLITE_PRIVATE void sqlite3ConnectionUnlocked(sqlite3 *db);
SQLITE_PRIVATE void sqlite3ConnectionClosed(sqlite3 *db);
#else
#define sqlite3ConnectionBlocked(x,y)
#define sqlite3ConnectionUnlocked(x)
#define sqlite3ConnectionClosed(x)
#endif
#ifdef SQLITE_DEBUG
SQLITE_PRIVATE void sqlite3ParserTrace(FILE*, char *);
#endif
#if defined(YYCOVERAGE)
SQLITE_PRIVATE int sqlite3ParserCoverage(FILE*);
#endif
sqlite3_vfs *pVfs,
const char *zPath,
sqlite3_file *pFile,
int flags,
int *pFlagsOut
){
int rc;
DO_OS_MALLOC_TEST(0);
/* 0x87f7f is a mask of SQLITE_OPEN_ flags that are valid to be passed
** down into the VFS layer. Some SQLITE_OPEN_ flags (for example,
** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
** reaching the VFS. */
assert( zPath || (flags & SQLITE_OPEN_EXCLUSIVE) );
rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x1087f7f, pFlagsOut);
assert( rc==SQLITE_OK || pFile->pMethods==0 );
return rc;
}
SQLITE_PRIVATE int sqlite3OsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
DO_OS_MALLOC_TEST(0);
assert( dirSync==0 || dirSync==1 );
return pVfs->xDelete!=0 ? pVfs->xDelete(pVfs, zPath, dirSync) : SQLITE_OK;
SQLITE3_MUTEX_INITIALIZER(11),
SQLITE3_MUTEX_INITIALIZER(12),
SQLITE3_MUTEX_INITIALIZER(13)
};
static int winMutex_isInit = 0;
static int winMutex_isNt = -1; /* <0 means "need to query" */
/* As the winMutexInit() and winMutexEnd() functions are called as part
** of the sqlite3_initialize() and sqlite3_shutdown() processing, the
** "interlocked" magic used here is probably not strictly necessary.
*/
static LONG SQLITE_WIN32_VOLATILE winMutex_lock = 0;
SQLITE_API int sqlite3_win32_is_nt(void); /* os_win.c */
SQLITE_API void sqlite3_win32_sleep(DWORD milliseconds); /* os_win.c */
static int winMutexInit(void){
/* The first to increment to 1 does actual initialization */
if( InterlockedCompareExchange(&winMutex_lock, 1, 0)==0 ){
int i;
for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
#if SQLITE_OS_WINRT
InitializeCriticalSectionEx(&winMutex_staticMutexes[i].mutex, 0, 0);
#else
InitializeCriticalSection(&winMutex_staticMutexes[i].mutex);
#endif
}
winMutex_isInit = 1;
}else{
while( !winMutex_isInit ){
sqlite3_win32_sleep(1);
}
}
return SQLITE_OK;
}
static int winMutexEnd(void){
/* The first to decrement to 0 does actual shutdown
** (which should be the last to shutdown.) */
if( InterlockedCompareExchange(&winMutex_lock, 0, 1)==1 ){
if( winMutex_isInit==1 ){
int i;
for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
DeleteCriticalSection(&winMutex_staticMutexes[i].mutex);
}
winMutex_isInit = 0;
}
}
return SQLITE_OK;
}
default: {
#ifdef SQLITE_ENABLE_API_ARMOR
if( iType-2<0 || iType-2>=ArraySize(winMutex_staticMutexes) ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
p = &winMutex_staticMutexes[iType-2];
#ifdef SQLITE_DEBUG
#ifdef SQLITE_WIN32_MUTEX_TRACE_STATIC
InterlockedCompareExchange(&p->trace, 1, 0);
#endif
#endif
break;
}
}
assert( p==0 || p->id==iType );
return p;
}
** canonical filename and implemented in the previous division.)
**
** The sqlite3_file structure for POSIX is no longer just an integer file
** descriptor. It is now a structure that holds the integer file
** descriptor and a pointer to a structure that describes the internal
** locks on the corresponding inode. There is one locking structure
** per inode, so if the same inode is opened twice, both unixFile structures
** point to the same locking structure. The locking structure keeps
** a reference count (so we will know when to delete it) and a "cnt"
** field that tells us its internal lock status. cnt==0 means the
** file is unlocked. cnt==-1 means the file has an exclusive lock.
** cnt>0 means there are cnt shared locks on the file.
**
** Any attempt to lock or unlock a file first checks the locking
** structure. The fcntl() system call is only invoked to set a
** POSIX lock if the internal lock structure transitions between
** a locked and an unlocked state.
**
** But wait: there are yet more problems with POSIX advisory locks.
**
** If you close a file descriptor that points to a file that has locks,
** all locks on that file that are owned by the current process are
** released. To work around this problem, each unixInodeInfo object
** maintains a count of the number of pending locks on the inode.
** When an attempt is made to close an unixFile, if there are
** other unixFile open on the same inode that are holding locks, the call
** to close() the file descriptor is deferred until all of the locks clear.
** lock primitives (called read-locks and write-locks below, to avoid
** confusion with SQLite lock names). The algorithms are complicated
** slightly in order to be compatible with Windows95 systems simultaneously
** accessing the same database file, in case that is ever required.
**
** Symbols defined in os.h identify the 'pending byte' and the 'reserved
** byte', each single bytes at well known offsets, and the 'shared byte
** range', a range of 510 bytes at a well known offset.
**
** To obtain a SHARED lock, a read-lock is obtained on the 'pending
** byte'. If this is successful, 'shared byte range' is read-locked
** and the lock on the 'pending byte' released. (Legacy note: When
** SQLite was first developed, Windows95 systems were still very common,
** and Windows95 lacks a shared-lock capability. So on Windows95, a
** single randomly selected by from the 'shared byte range' is locked.
** Windows95 is now pretty much extinct, but this work-around for the
** lack of shared-locks on Windows95 lives on, for backwards
** compatibility.)
**
** A process may only obtain a RESERVED lock after it has a SHARED lock.
** A RESERVED lock is implemented by grabbing a write-lock on the
** 'reserved byte'.
**
** An EXCLUSIVE lock may only be requested after either a SHARED or
** RESERVED lock is held. An EXCLUSIVE lock is implemented by obtaining
** unixFile, do nothing. Don't use the end_lock: exit path, as
** unixEnterMutex() hasn't been called yet.
*/
if( pFile->eFileLock>=eFileLock ){
OSTRACE(("LOCK %d %s ok (already held) (unix)\n", pFile->h,
azFileLock(eFileLock)));
return SQLITE_OK;
}
/* Make sure the locking sequence is correct.
** (1) We never move from unlocked to anything higher than shared lock.
** (2) SQLite never explicitly requests a pending lock.
** (3) A shared lock is always held when a reserve lock is requested.
*/
assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
assert( eFileLock!=PENDING_LOCK );
assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
/* This mutex is needed because pFile->pInode is shared across threads
*/
pInode = pFile->pInode;
}
/*
** Lower the locking level on file descriptor pFile to eFileLock. eFileLock
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
**
** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
** the byte range is divided into 2 parts and the first part is unlocked then
** set to a read lock, then the other part is simply unlocked. This works
** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to
** remove the write lock on a region when a read lock is set.
*/
static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
unixFile *pFile = (unixFile*)id;
unixInodeInfo *pInode;
struct flock lock;
int rc = SQLITE_OK;
assert( pFile );
#define DOTLOCK_SUFFIX ".lock"
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
**
** In dotfile locking, either a lock exists or it does not. So in this
** variation of CheckReservedLock(), *pResOut is set to true if any lock
** is held on the file and false if the file is unlocked.
*/
static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
int rc = SQLITE_OK;
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
reserved = osAccess((const char*)pFile->lockingContext, 0)==0;
int rc = SQLITE_OK;
/* if we already have a lock, it is exclusive.
** Just adjust level and punt on outta here. */
if (pFile->eFileLock > NO_LOCK) {
pFile->eFileLock = eFileLock;
rc = SQLITE_OK;
goto sem_end_lock;
}
/* lock semaphore now but bail out when already locked. */
if( sem_trywait(pSem)==-1 ){
rc = SQLITE_BUSY;
goto sem_end_lock;
}
/* got it, set the type and return ok */
pFile->eFileLock = eFileLock;
sem_end_lock:
return rc;
typedef struct afpLockingContext afpLockingContext;
struct afpLockingContext {
int reserved;
const char *dbPath; /* Name of the open file */
};
struct ByteRangeLockPB2
{
unsigned long long offset; /* offset to first byte to lock */
unsigned long long length; /* nbr of bytes to lock */
unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
unsigned char unLockFlag; /* 1 = unlock, 0 = lock */
unsigned char startEndFlag; /* 1=rel to end of fork, 0=rel to start */
int fd; /* file desc to assoc this lock with */
};
#define afpfsByteRangeLock2FSCTL _IOWR('z', 23, struct ByteRangeLockPB2)
/*
** This is a utility for setting or clearing a bit-range lock on an
** AFP filesystem.
**
** Return SQLITE_OK on success, SQLITE_BUSY on failure.
*/
static int afpSetLock(
const char *path, /* Name of the file to be locked or unlocked */
unixFile *pFile, /* Open file descriptor on path */
unsigned long long offset, /* First byte to be locked */
unsigned long long length, /* Number of bytes to lock */
int setLockFlag /* True to set lock. False to clear lock */
){
struct ByteRangeLockPB2 pb;
int err;
pb.unLockFlag = setLockFlag ? 0 : 1;
pb.startEndFlag = 0;
pb.offset = offset;
pb.length = length;
** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
** unixEnterMutex() hasn't been called yet.
*/
if( pFile->eFileLock>=eFileLock ){
OSTRACE(("LOCK %d %s ok (already held) (afp)\n", pFile->h,
azFileLock(eFileLock)));
return SQLITE_OK;
}
/* Make sure the locking sequence is correct
** (1) We never move from unlocked to anything higher than shared lock.
** (2) SQLite never explicitly requests a pending lock.
** (3) A shared lock is always held when a reserve lock is requested.
*/
assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
assert( eFileLock!=PENDING_LOCK );
assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
/* This mutex is needed because pFile->pInode is shared across threads
*/
pInode = pFile->pInode;
** lock corresponding to slot iSlot, mutex aMutex[iSlot] must be held.
*/
struct unixShmNode {
unixInodeInfo *pInode; /* unixInodeInfo that owns this SHM node */
sqlite3_mutex *pShmMutex; /* Mutex to access this object */
char *zFilename; /* Name of the mmapped file */
int hShm; /* Open file descriptor */
int szRegion; /* Size of shared-memory regions */
u16 nRegion; /* Size of array apRegion */
u8 isReadonly; /* True if read-only */
u8 isUnlocked; /* True if no DMS lock held */
char **apRegion; /* Array of mapped shared-memory regions */
int nRef; /* Number of unixShm objects pointing to this */
unixShm *pFirst; /* All unixShm objects pointing to this */
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
sqlite3_mutex *aMutex[SQLITE_SHM_NLOCK];
#endif
int aLock[SQLITE_SHM_NLOCK]; /* # shared locks on slot, -1==excl lock */
#ifdef SQLITE_DEBUG
u8 nextShmId; /* Next available unixShm.id value */
#endif
p->pInode->pShmNode = 0;
sqlite3_free(p);
}
}
/*
** The DMS lock has not yet been taken on shm file pShmNode. Attempt to
** take it now. Return SQLITE_OK if successful, or an SQLite error
** code otherwise.
**
** If the DMS cannot be locked because this is a readonly_shm=1
** connection and no other process already holds a lock, return
** SQLITE_READONLY_CANTINIT and set pShmNode->isUnlocked=1.
*/
static int unixLockSharedMemory(unixFile *pDbFd, unixShmNode *pShmNode){
struct flock lock;
int rc = SQLITE_OK;
/* Use F_GETLK to determine the locks other processes are holding
** on the DMS byte. If it indicates that another process is holding
** a SHARED lock, then this process may also take a SHARED lock
** and proceed with opening the *-shm file.
**
** And if the *-shm file has been corrupted by a power failure or
** system crash, the database itself may also become corrupt. */
lock.l_whence = SEEK_SET;
lock.l_start = UNIX_SHM_DMS;
lock.l_len = 1;
lock.l_type = F_WRLCK;
if( osFcntl(pShmNode->hShm, F_GETLK, &lock)!=0 ) {
rc = SQLITE_IOERR_LOCK;
}else if( lock.l_type==F_UNLCK ){
if( pShmNode->isReadonly ){
pShmNode->isUnlocked = 1;
rc = SQLITE_READONLY_CANTINIT;
}else{
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
/* Do not use a blocking lock here. If the lock cannot be obtained
** immediately, it means some other connection is truncating the
** *-shm file. And after it has done so, it will not release its
** lock, but only downgrade it to a shared lock. So no point in
** blocking here. The call below to obtain the shared DMS lock may
** use a blocking lock. */
int iSaveTimeout = pDbFd->iBusyTimeout;
/* If the shared-memory file has not yet been opened, open it now. */
if( pDbFd->pShm==0 ){
rc = unixOpenSharedMemory(pDbFd);
if( rc!=SQLITE_OK ) return rc;
}
p = pDbFd->pShm;
pShmNode = p->pShmNode;
sqlite3_mutex_enter(pShmNode->pShmMutex);
if( pShmNode->isUnlocked ){
rc = unixLockSharedMemory(pDbFd, pShmNode);
if( rc!=SQLITE_OK ) goto shmpage_out;
pShmNode->isUnlocked = 0;
}
assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
assert( pShmNode->pInode==pDbFd->pInode );
assert( pShmNode->hShm>=0 || pDbFd->pInode->bProcessLock==1 );
assert( pShmNode->hShm<0 || pDbFd->pInode->bProcessLock==0 );
/* Minimum number of regions required to be mapped. */
nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;
if( pShmNode->nRegion<nReqRegion ){
assert( 0==memcmp(pShmNode->aLock, aLock, sizeof(aLock)) );
return (memcmp(pShmNode->aLock, aLock, sizeof(aLock))==0);
#endif
}
#endif
/*
** Change the lock state for a shared-memory segment.
**
** Note that the relationship between SHARED and EXCLUSIVE locks is a little
** different here than in posix. In xShmLock(), one can go from unlocked
** to shared and back or from unlocked to exclusive and back. But one may
** not go from shared to exclusive or from exclusive to shared.
*/
static int unixShmLock(
sqlite3_file *fd, /* Database file holding the shared memory */
int ofst, /* First lock to acquire or release */
int n, /* Number of locks to acquire or release */
int flags /* What to do with the lock */
){
unixFile *pDbFd = (unixFile*)fd; /* Connection holding shared memory */
unixShm *p; /* The shared memory being locked */
unixShmNode *pShmNode; /* The underlying file iNode */
int rc = SQLITE_OK; /* Result code */
u16 mask = (1<<(ofst+n)) - (1<<ofst); /* Mask of locks to take or release */
int *aLock;
p = pDbFd->pShm;
if( p==0 ) return SQLITE_IOERR_SHMLOCK;
pShmNode = p->pShmNode;
if( NEVER(pShmNode==0) ) return SQLITE_IOERR_SHMLOCK;
aLock = pShmNode->aLock;
|| (flags==(SQLITE_SHM_EXCLUSIVE|SQLITE_SHM_LOCK))
){
/* Take the required mutexes. In SETLK_TIMEOUT mode (blocking locks), if
** this is an attempt on an exclusive lock use sqlite3_mutex_try(). If any
** other thread is holding this mutex, then it is either holding or about
** to hold a lock exclusive to the one being requested, and we may
** therefore return SQLITE_BUSY to the caller.
**
** Doing this prevents some deadlock scenarios. For example, thread 1 may
** be a checkpointer blocked waiting on the WRITER lock. And thread 2
** may be a normal SQL client upgrading to a write transaction. In this
** case thread 2 does a non-blocking request for the WRITER lock. But -
** if it were to use sqlite3_mutex_enter() then it would effectively
** become a (doomed) blocking request, as thread 2 would block until thread
** 1 obtained WRITER and released the mutex. Since thread 2 already holds
** a lock on a read-locking slot at this point, this breaks the
** anti-deadlock rules (see above). */
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
int iMutex;
for(iMutex=ofst; iMutex<ofst+n; iMutex++){
#endif
if( ALWAYS(rc==SQLITE_OK) ){
if( flags & SQLITE_SHM_UNLOCK ){
/* Case (a) - unlock. */
int bUnlock = 1;
assert( (p->exclMask & p->sharedMask)==0 );
assert( !(flags & SQLITE_SHM_EXCLUSIVE) || (p->exclMask & mask)==mask );
assert( !(flags & SQLITE_SHM_SHARED) || (p->sharedMask & mask)==mask );
/* If this is a SHARED lock being unlocked, it is possible that other
** clients within this process are holding the same SHARED lock. In
** this case, set bUnlock to 0 so that the posix lock is not removed
** from the file-descriptor below. */
if( flags & SQLITE_SHM_SHARED ){
assert( n==1 );
assert( aLock[ofst]>=1 );
if( aLock[ofst]>1 ){
bUnlock = 0;
aLock[ofst]--;
p->sharedMask &= ~mask;
{ "smbfs", &afpIoMethods },
{ "webdav", &nolockIoMethods },
{ 0, 0 }
};
int i;
struct statfs fsInfo;
struct flock lockInfo;
if( !filePath ){
/* If filePath==NULL that means we are dealing with a transient file
** that does not need to be locked. */
return &nolockIoMethods;
}
if( statfs(filePath, &fsInfo) != -1 ){
if( fsInfo.f_flags & MNT_RDONLY ){
return &nolockIoMethods;
}
for(i=0; aMap[i].zFilesystem; i++){
if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){
return aMap[i].pMethods;
}
** work, then fallback to named semaphore locking.
*/
static const sqlite3_io_methods *vxworksIoFinderImpl(
const char *filePath, /* name of the database file */
unixFile *pNew /* the open file object */
){
struct flock lockInfo;
if( !filePath ){
/* If filePath==NULL that means we are dealing with a transient file
** that does not need to be locked. */
return &nolockIoMethods;
}
/* Test if fcntl() is supported and use POSIX style locks.
** Otherwise fall back to the named semaphore method.
*/
lockInfo.l_len = 1;
lockInfo.l_start = 0;
lockInfo.l_whence = SEEK_SET;
lockInfo.l_type = F_RDLCK;
#if SQLITE_OS_WINRT && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
{ "CreateFileMappingFromApp", (SYSCALL)CreateFileMappingFromApp, 0 },
#else
{ "CreateFileMappingFromApp", (SYSCALL)0, 0 },
#endif
#define osCreateFileMappingFromApp ((HANDLE(WINAPI*)(HANDLE, \
LPSECURITY_ATTRIBUTES,ULONG,ULONG64,LPCWSTR))aSyscall[75].pCurrent)
/*
** NOTE: On some sub-platforms, the InterlockedCompareExchange "function"
** is really just a macro that uses a compiler intrinsic (e.g. x64).
** So do not try to make this is into a redefinable interface.
*/
#if defined(InterlockedCompareExchange)
{ "InterlockedCompareExchange", (SYSCALL)0, 0 },
#define osInterlockedCompareExchange InterlockedCompareExchange
#else
{ "InterlockedCompareExchange", (SYSCALL)InterlockedCompareExchange, 0 },
#define osInterlockedCompareExchange ((LONG(WINAPI*)(LONG \
SQLITE_WIN32_VOLATILE*, LONG,LONG))aSyscall[76].pCurrent)
#endif /* defined(InterlockedCompareExchange) */
#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
{ "UuidCreate", (SYSCALL)UuidCreate, 0 },
#else
{ "UuidCreate", (SYSCALL)0, 0 },
#endif
#define osUuidCreate ((RPC_STATUS(RPC_ENTRY*)(UUID*))aSyscall[77].pCurrent)
#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
** based on the NT kernel.
*/
SQLITE_API int sqlite3_win32_is_nt(void){
#if SQLITE_OS_WINRT
/*
** NOTE: The WinRT sub-platform is always assumed to be based on the NT
** kernel.
*/
return 1;
#elif SQLITE_WIN32_GETVERSIONEX
if( osInterlockedCompareExchange(&sqlite3_os_type, 0, 0)==0 ){
#if defined(SQLITE_WIN32_HAS_ANSI)
OSVERSIONINFOA sInfo;
sInfo.dwOSVersionInfoSize = sizeof(sInfo);
osGetVersionExA(&sInfo);
osInterlockedCompareExchange(&sqlite3_os_type,
(sInfo.dwPlatformId == VER_PLATFORM_WIN32_NT) ? 2 : 1, 0);
#elif defined(SQLITE_WIN32_HAS_WIDE)
OSVERSIONINFOW sInfo;
sInfo.dwOSVersionInfoSize = sizeof(sInfo);
osGetVersionExW(&sInfo);
osInterlockedCompareExchange(&sqlite3_os_type,
(sInfo.dwPlatformId == VER_PLATFORM_WIN32_NT) ? 2 : 1, 0);
#endif
}
return osInterlockedCompareExchange(&sqlite3_os_type, 2, 2)==2;
#elif SQLITE_TEST
return osInterlockedCompareExchange(&sqlite3_os_type, 2, 2)==2;
#else
/*
** NOTE: All sub-platforms where the GetVersionEx[AW] functions are
** deprecated are always assumed to be based on the NT kernel.
*/
return 1;
#endif
}
#ifdef SQLITE_WIN32_MALLOC
**
*/
struct winShmNode {
sqlite3_mutex *mutex; /* Mutex to access this object */
char *zFilename; /* Name of the file */
winFile hFile; /* File handle from winOpen */
int szRegion; /* Size of shared-memory regions */
int nRegion; /* Size of array apRegion */
u8 isReadonly; /* True if read-only */
u8 isUnlocked; /* True if no DMS lock held */
struct ShmRegion {
HANDLE hMap; /* File handle from CreateFileMapping */
void *pMap;
} *aRegion;
DWORD lastErrno; /* The Windows errno from the last I/O error */
int nRef; /* Number of winShm objects pointing to this */
winShm *pFirst; /* All winShm objects pointing to this */
winShmNode *pNext; /* Next in list of all winShmNode objects */
/*
** Apply advisory locks for all n bytes beginning at ofst.
*/
#define WINSHM_UNLCK 1
#define WINSHM_RDLCK 2
#define WINSHM_WRLCK 3
static int winShmSystemLock(
winShmNode *pFile, /* Apply locks to this open shared-memory segment */
int lockType, /* WINSHM_UNLCK, WINSHM_RDLCK, or WINSHM_WRLCK */
int ofst, /* Offset to first byte to be locked/unlocked */
int nByte /* Number of bytes to lock or unlock */
){
int rc = 0; /* Result code form Lock/UnlockFileEx() */
/* Access to the winShmNode object is serialized by the caller */
assert( pFile->nRef==0 || sqlite3_mutex_held(pFile->mutex) );
OSTRACE(("SHM-LOCK file=%p, lock=%d, offset=%d, size=%d\n",
pFile->hFile.h, lockType, ofst, nByte));
pp = &p->pNext;
}
}
}
/*
** The DMS lock has not yet been taken on shm file pShmNode. Attempt to
** take it now. Return SQLITE_OK if successful, or an SQLite error
** code otherwise.
**
** If the DMS cannot be locked because this is a readonly_shm=1
** connection and no other process already holds a lock, return
** SQLITE_READONLY_CANTINIT and set pShmNode->isUnlocked=1.
*/
static int winLockSharedMemory(winShmNode *pShmNode){
int rc = winShmSystemLock(pShmNode, WINSHM_WRLCK, WIN_SHM_DMS, 1);
if( rc==SQLITE_OK ){
if( pShmNode->isReadonly ){
pShmNode->isUnlocked = 1;
winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
return SQLITE_READONLY_CANTINIT;
}else if( winTruncate((sqlite3_file*)&pShmNode->hFile, 0) ){
winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
return winLogError(SQLITE_IOERR_SHMOPEN, osGetLastError(),
"winLockSharedMemory", pShmNode->zFilename);
}
}
if( rc==SQLITE_OK ){
/*
** Change the lock state for a shared-memory segment.
*/
static int winShmLock(
sqlite3_file *fd, /* Database file holding the shared memory */
int ofst, /* First lock to acquire or release */
int n, /* Number of locks to acquire or release */
int flags /* What to do with the lock */
){
winFile *pDbFd = (winFile*)fd; /* Connection holding shared memory */
winShm *p = pDbFd->pShm; /* The shared memory being locked */
winShm *pX; /* For looping over all siblings */
winShmNode *pShmNode;
int rc = SQLITE_OK; /* Result code */
u16 mask; /* Mask of locks to take or release */
if( p==0 ) return SQLITE_IOERR_SHMLOCK;
pShmNode = p->pShmNode;
if( NEVER(pShmNode==0) ) return SQLITE_IOERR_SHMLOCK;
assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
** lock. If any do, return SQLITE_BUSY right away.
*/
for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
rc = SQLITE_BUSY;
break;
}
}
/* Get the exclusive locks at the system level. Then if successful
** also mark the local connection as being locked.
*/
if( rc==SQLITE_OK ){
rc = winShmSystemLock(pShmNode, WINSHM_WRLCK, ofst+WIN_SHM_BASE, n);
if( rc==SQLITE_OK ){
assert( (p->sharedMask & mask)==0 );
p->exclMask |= mask;
}
}
}
sqlite3_mutex_leave(pShmNode->mutex);
if( !pShm ){
rc = winOpenSharedMemory(pDbFd);
if( rc!=SQLITE_OK ) return rc;
pShm = pDbFd->pShm;
assert( pShm!=0 );
}
pShmNode = pShm->pShmNode;
sqlite3_mutex_enter(pShmNode->mutex);
if( pShmNode->isUnlocked ){
rc = winLockSharedMemory(pShmNode);
if( rc!=SQLITE_OK ) goto shmpage_out;
pShmNode->isUnlocked = 0;
}
assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
if( pShmNode->nRegion<=iRegion ){
struct ShmRegion *apNew; /* New aRegion[] array */
int nByte = (iRegion+1)*szRegion; /* Minimum required file size */
sqlite3_int64 sz; /* Current size of wal-index file */
pShmNode->szRegion = szRegion;
** WRITER_DBMOD -> WRITER_FINISHED [sqlite3PagerCommitPhaseOne]
** WRITER_*** -> READER [pager_end_transaction]
**
** WRITER_*** -> ERROR [pager_error]
** ERROR -> OPEN [pager_unlock]
**
**
** OPEN:
**
** The pager starts up in this state. Nothing is guaranteed in this
** state - the file may or may not be locked and the database size is
** unknown. The database may not be read or written.
**
** * No read or write transaction is active.
** * Any lock, or no lock at all, may be held on the database file.
** * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
**
** READER:
**
** In this state all the requirements for reading the database in
** rollback (non-WAL) mode are met. Unless the pager is (or recently
** pagerUnlockDb() take a conservative approach - eLock is always updated
** when unlocking the file, and only updated when locking the file if the
** VFS call is successful. This way, the Pager.eLock variable may be set
** to a less exclusive (lower) value than the lock that is actually held
** at the system level, but it is never set to a more exclusive value.
**
** This is usually safe. If an xUnlock fails or appears to fail, there may
** be a few redundant xLock() calls or a lock may be held for longer than
** required, but nothing really goes wrong.
**
** The exception is when the database file is unlocked as the pager moves
** from ERROR to OPEN state. At this point there may be a hot-journal file
** in the file-system that needs to be rolled back (as part of an OPEN->SHARED
** transition, by the same pager or any other). If the call to xUnlock()
** fails at this point and the pager is left holding an EXCLUSIVE lock, this
** can confuse the call to xCheckReservedLock() call made later as part
** of hot-journal detection.
**
** xCheckReservedLock() is defined as returning true "if there is a RESERVED
** lock held by this process or any others". So xCheckReservedLock may
** return true because the caller itself is holding an EXCLUSIVE lock (but
}
return rc;
}
/*
** This function is a no-op if the pager is in exclusive mode and not
** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
** state.
**
** If the pager is not in exclusive-access mode, the database file is
** completely unlocked. If the file is unlocked and the file-system does
** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
** closed (if it is open).
**
** If the pager is in ERROR state when this function is called, the
** contents of the pager cache are discarded before switching back to
** the OPEN state. Regardless of whether the pager is in exclusive-mode
** or not, any journal file left in the file-system will be treated
** as a hot-journal and rolled back the next time a read-transaction
** is opened (by this or by any other connection).
*/
** Ticket #1171: The statement journal might contain page content that is
** different from the page content at the start of the transaction.
** This occurs when a page is changed prior to the start of a statement
** then changed again within the statement. When rolling back such a
** statement we must not write to the original database unless we know
** for certain that original page contents are synced into the main rollback
** journal. Otherwise, a power loss might leave modified data in the
** database file without an entry in the rollback journal that can
** restore the database to its original form. Two conditions must be
** met before writing to the database files. (1) the database must be
** locked. (2) we know that the original page content is fully synced
** in the main journal either because the page is not in cache or else
** the page is marked as needSync==0.
**
** 2008-04-14: When attempting to vacuum a corrupt database file, it
** is possible to fail a statement on a database that does not yet exist.
** Do not attempt to write if database file has never been opened.
*/
if( pagerUseWal(pPager) ){
pPg = 0;
}else{
assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
));
*pExists = 0;
if( !jrnlOpen ){
rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
}
if( rc==SQLITE_OK && exists ){
int locked = 0; /* True if some process holds a RESERVED lock */
/* Race condition here: Another process might have been holding the
** the RESERVED lock and have a journal open at the sqlite3OsAccess()
** call above, but then delete the journal and drop the lock before
** we get to the following sqlite3OsCheckReservedLock() call. If that
** is the case, this routine might think there is a hot journal when
** in fact there is none. This results in a false-positive which will
** be dealt with by the playback routine. Ticket #3883.
*/
rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
if( rc==SQLITE_OK && !locked ){
Pgno nPage; /* Number of pages in database file */
assert( pPager->tempFile==0 );
rc = pagerPagecount(pPager, &nPage);
if( rc==SQLITE_OK ){
/* If the database is zero pages in size, that means that either (1) the
** journal is a remnant from a prior database with the same name where
** the database file but not the journal was deleted, or (2) the initial
** transaction that populates a new database is being rolled back.
** In either case, the journal file can be deleted. However, take care
lockIdx-WAL_READ_LOCK(0));
return zName;
}
}
#endif /*defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
/*
** Set or release locks on the WAL. Locks are either shared or exclusive.
** A lock cannot be moved directly between shared and exclusive - it must go
** through the unlocked state first.
**
** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
*/
static int walLockShared(Wal *pWal, int lockIdx){
int rc;
if( pWal->exclusiveMode ) return SQLITE_OK;
rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
SQLITE_SHM_LOCK | SQLITE_SHM_SHARED);
WALTRACE(("WAL%p: acquire SHARED-%s %s\n", pWal,
walLockName(lockIdx), rc ? "failed" : "ok"));
** that this thread is running recovery. If unable to establish
** the necessary locks, this routine returns SQLITE_BUSY.
*/
static int walIndexRecover(Wal *pWal){
int rc; /* Return Code */
i64 nSize; /* Size of log file */
u32 aFrameCksum[2] = {0, 0};
int iLock; /* Lock offset to lock for checkpoint */
/* Obtain an exclusive lock on all byte in the locking range not already
** locked by the caller. The caller is guaranteed to have locked the
** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
** If successful, the same bytes that are locked here are unlocked before
** this function returns.
*/
assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
assert( pWal->writeLock );
iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
rc = walLockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
if( rc ){
return rc;
volatile WalCkptInfo *pInfo; /* Checkpoint information in wal-index */
u32 mxReadMark; /* Largest aReadMark[] value */
int mxI; /* Index of largest aReadMark[] value */
int i; /* Loop counter */
int rc = SQLITE_OK; /* Return code */
u32 mxFrame; /* Wal frame to lock to */
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
int nBlockTmout = 0;
#endif
assert( pWal->readLock<0 ); /* Not currently locked */
/* useWal may only be set for read/write connections */
assert( (pWal->readOnly & WAL_SHM_RDONLY)==0 || useWal==0 );
/* Take steps to avoid spinning forever if there is a protocol error.
**
** Circumstances that cause a RETRY should only last for the briefest
** instances of time. No I/O or other system calls are done while the
** locks are held, so the locks should not be held for very long. But
** if we are unlucky, another process that is holding a lock might get
** The pBt pointer itself may not be changed while there exists cursors
** in the referenced BtShared that point back to this Btree since those
** cursors have to go through this Btree to find their BtShared and
** they often do so without holding sqlite3.mutex.
*/
struct Btree {
sqlite3 *db; /* The database connection holding this btree */
BtShared *pBt; /* Sharable content of this btree */
u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
u8 sharable; /* True if we can share pBt with another db */
u8 locked; /* True if db currently has pBt locked */
u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
int nBackup; /* Number of backup operations reading this btree */
u32 iBDataVersion; /* Combines with pBt->pPager->iDataVersion */
Btree *pNext; /* List of other sharable Btrees from the same db */
Btree *pPrev; /* Back pointer of the same list */
#ifdef SQLITE_DEBUG
u64 nSeek; /* Calls to sqlite3BtreeMovetoUnpacked() */
#endif
#ifndef SQLITE_OMIT_SHARED_CACHE
#endif
/************** End of btreeInt.h ********************************************/
/************** Continuing where we left off in btmutex.c ********************/
#ifndef SQLITE_OMIT_SHARED_CACHE
#if SQLITE_THREADSAFE
/*
** Obtain the BtShared mutex associated with B-Tree handle p. Also,
** set BtShared.db to the database handle associated with p and the
** p->locked boolean to true.
*/
static void lockBtreeMutex(Btree *p){
assert( p->locked==0 );
assert( sqlite3_mutex_notheld(p->pBt->mutex) );
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3_mutex_enter(p->pBt->mutex);
p->pBt->db = p->db;
p->locked = 1;
}
/*
** Release the BtShared mutex associated with B-Tree handle p and
** clear the p->locked boolean.
*/
static void SQLITE_NOINLINE unlockBtreeMutex(Btree *p){
BtShared *pBt = p->pBt;
assert( p->locked==1 );
assert( sqlite3_mutex_held(pBt->mutex) );
assert( sqlite3_mutex_held(p->db->mutex) );
assert( p->db==pBt->db );
sqlite3_mutex_leave(pBt->mutex);
p->locked = 0;
}
/* Forward reference */
static void SQLITE_NOINLINE btreeLockCarefully(Btree *p);
/*
** Enter a mutex on the given BTree object.
**
** If the object is not sharable, then no mutex is ever required
** and this routine is a no-op. The underlying mutex is non-recursive.
** But we keep a reference count in Btree.wantToLock so the behavior
** of this interface is recursive.
**
** To avoid deadlocks, multiple Btrees are locked in the same order
** by all database connections. The p->pNext is a list of other
** Btrees belonging to the same database connection as the p Btree
** which need to be locked after p. If we cannot get a lock on
** p, then first unlock all of the others on p->pNext, then wait
** for the lock to become available on p, then relock all of the
** subsequent Btrees that desire a lock.
*/
SQLITE_PRIVATE void sqlite3BtreeEnter(Btree *p){
/* Some basic sanity checking on the Btree. The list of Btrees
** connected by pNext and pPrev should be in sorted order by
** Btree.pBt value. All elements of the list should belong to
** the same connection. Only shared Btrees are on the list. */
assert( p->pNext==0 || p->pNext->pBt>p->pBt );
assert( p->pPrev==0 || p->pPrev->pBt<p->pBt );
assert( p->pNext==0 || p->pNext->db==p->db );
assert( p->pPrev==0 || p->pPrev->db==p->db );
assert( p->sharable || (p->pNext==0 && p->pPrev==0) );
/* Check for locking consistency */
assert( !p->locked || p->wantToLock>0 );
assert( p->sharable || p->wantToLock==0 );
/* We should already hold a lock on the database connection */
assert( sqlite3_mutex_held(p->db->mutex) );
/* Unless the database is sharable and unlocked, then BtShared.db
** should already be set correctly. */
assert( (p->locked==0 && p->sharable) || p->pBt->db==p->db );
if( !p->sharable ) return;
p->wantToLock++;
if( p->locked ) return;
btreeLockCarefully(p);
}
/* This is a helper function for sqlite3BtreeLock(). By moving
** complex, but seldom used logic, out of sqlite3BtreeLock() and
** into this routine, we avoid unnecessary stack pointer changes
** and thus help the sqlite3BtreeLock() routine to run much faster
** in the common case.
*/
static void SQLITE_NOINLINE btreeLockCarefully(Btree *p){
Btree *pLater;
/* In most cases, we should be able to acquire the lock we
** want without having to go through the ascending lock
** procedure that follows. Just be sure not to block.
*/
if( sqlite3_mutex_try(p->pBt->mutex)==SQLITE_OK ){
p->pBt->db = p->db;
p->locked = 1;
return;
}
/* To avoid deadlock, first release all locks with a larger
** BtShared address. Then acquire our lock. Then reacquire
** the other BtShared locks that we used to hold in ascending
** order.
*/
for(pLater=p->pNext; pLater; pLater=pLater->pNext){
assert( pLater->sharable );
assert( pLater->pNext==0 || pLater->pNext->pBt>pLater->pBt );
assert( !pLater->locked || pLater->wantToLock>0 );
if( pLater->locked ){
unlockBtreeMutex(pLater);
}
}
lockBtreeMutex(p);
for(pLater=p->pNext; pLater; pLater=pLater->pNext){
if( pLater->wantToLock ){
lockBtreeMutex(pLater);
}
}
}
}
#ifndef NDEBUG
/*
** Return true if the BtShared mutex is held on the btree, or if the
** B-Tree is not marked as sharable.
**
** This routine is used only from within assert() statements.
*/
SQLITE_PRIVATE int sqlite3BtreeHoldsMutex(Btree *p){
assert( p->sharable==0 || p->locked==0 || p->wantToLock>0 );
assert( p->sharable==0 || p->locked==0 || p->db==p->pBt->db );
assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->pBt->mutex) );
assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->db->mutex) );
return (p->sharable==0 || p->locked);
}
#endif
/*
** Enter the mutex on every Btree associated with a database
** connection. This is needed (for example) prior to parsing
** a statement since we will be comparing table and column names
** against all schemas and we do not want those schemas being
** reset out from under us.
SQLITE_PRIVATE int sqlite3SchemaMutexHeld(sqlite3 *db, int iDb, Schema *pSchema){
Btree *p;
assert( db!=0 );
if( db->pVfs==0 && db->nDb==0 ) return 1;
if( pSchema ) iDb = sqlite3SchemaToIndex(db, pSchema);
assert( iDb>=0 && iDb<db->nDb );
if( !sqlite3_mutex_held(db->mutex) ) return 0;
if( iDb==1 ) return 1;
p = db->aDb[iDb].pBt;
assert( p!=0 );
return p->sharable==0 || p->locked==1;
}
#endif /* NDEBUG */
#else /* SQLITE_THREADSAFE>0 above. SQLITE_THREADSAFE==0 below */
/*
** The following are special cases for mutex enter routines for use
** in single threaded applications that use shared cache. Except for
** these two routines, all mutex operations are no-ops in that case and
** are null #defines in btree.h.
**
/* This routine is a no-op if the shared-cache is not enabled */
if( !p->sharable ){
return SQLITE_OK;
}
/* If some other connection is holding an exclusive lock, the
** requested lock may not be obtained.
*/
if( pBt->pWriter!=p && (pBt->btsFlags & BTS_EXCLUSIVE)!=0 ){
sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
return SQLITE_LOCKED_SHAREDCACHE;
}
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
/* The condition (pIter->eLock!=eLock) in the following if(...)
** statement is a simplification of:
**
** (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
**
** since we know that if eLock==WRITE_LOCK, then no other connection
** may hold a WRITE_LOCK on any table in this file (since there can
** only be a single writer).
*/
assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
if( eLock==WRITE_LOCK ){
assert( p==pBt->pWriter );
pBt->btsFlags |= BTS_PENDING;
}
return SQLITE_LOCKED_SHAREDCACHE;
}
}
return SQLITE_OK;
}
#endif /* !SQLITE_OMIT_SHARED_CACHE */
** The call to sqlite3BtreeRollback() drops any table-locks held by
** this handle.
*/
sqlite3BtreeRollback(p, SQLITE_OK, 0);
sqlite3BtreeLeave(p);
/* If there are still other outstanding references to the shared-btree
** structure, return now. The remainder of this procedure cleans
** up the shared-btree.
*/
assert( p->wantToLock==0 && p->locked==0 );
if( !p->sharable || removeFromSharingList(pBt) ){
/* The pBt is no longer on the sharing list, so we can access
** it without having to hold the mutex.
**
** Clean out and delete the BtShared object.
*/
assert( !pBt->pCursor );
sqlite3PagerClose(pBt->pPager, p->db);
if( pBt->xFreeSchema && pBt->pSchema ){
pBt->xFreeSchema(pBt->pSchema);
}
sqlite3DbFree(0, pBt->pSchema);
freeTempSpace(pBt);
sqlite3_free(pBt);
}
#ifndef SQLITE_OMIT_SHARED_CACHE
assert( p->wantToLock==0 );
assert( p->locked==0 );
if( p->pPrev ) p->pPrev->pNext = p->pNext;
if( p->pNext ) p->pNext->pPrev = p->pPrev;
#endif
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Change the "soft" limit on the number of pages in the cache.
/* Forward declaration */
static int newDatabase(BtShared*);
/*
** Get a reference to pPage1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory.
*/
static int lockBtree(BtShared *pBt){
int rc; /* Result code from subfunctions */
MemPage *pPage1; /* Page 1 of the database file */
u32 nPage; /* Number of pages in the database */
u32 nPageFile = 0; /* Number of pages in the database file */
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pBt->pPage1==0 );
**
** sqlite3BtreeCreateTable()
** sqlite3BtreeCreateIndex()
** sqlite3BtreeClearTable()
** sqlite3BtreeDropTable()
** sqlite3BtreeInsert()
** sqlite3BtreeDelete()
** sqlite3BtreeUpdateMeta()
**
** If an initial attempt to acquire the lock fails because of lock contention
** and the database was previously unlocked, then invoke the busy handler
** if there is one. But if there was previously a read-lock, do not
** invoke the busy handler - just return SQLITE_BUSY. SQLITE_BUSY is
** returned when there is already a read-lock in order to avoid a deadlock.
**
** Suppose there are two processes A and B. A has a read lock and B has
** a reserved lock. B tries to promote to exclusive but is blocked because
** of A's read lock. A tries to promote to reserved but is blocked by B.
** One or the other of the two processes must give way or there can be
** no progress. By returning SQLITE_BUSY and not invoking the busy callback
** when A already has a read lock, we encourage A to give up and let B
** proceed.
*/
static SQLITE_NOINLINE int btreeBeginTrans(
Btree *p, /* The btree in which to start the transaction */
int wrflag, /* True to start a write transaction */
int *pSchemaVersion /* Put schema version number here, if not NULL */
){
}else if( wrflag>1 ){
BtLock *pIter;
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p ){
pBlock = pIter->pBtree->db;
break;
}
}
}
if( pBlock ){
sqlite3ConnectionBlocked(p->db, pBlock);
rc = SQLITE_LOCKED_SHAREDCACHE;
goto trans_begun;
}
}
#endif
/* Any read-only or read-write transaction implies a read-lock on
** page 1. So if some other shared-cache client already has a write-lock
** on page 1, the transaction cannot be opened. */
rc = querySharedCacheTableLock(p, SCHEMA_ROOT, READ_LOCK);
sqlite3_backup *p; /* Value to return */
#ifdef SQLITE_ENABLE_API_ARMOR
if( !sqlite3SafetyCheckOk(pSrcDb)||!sqlite3SafetyCheckOk(pDestDb) ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
/* Lock the source database handle. The destination database
** handle is not locked in this routine, but it is locked in
** sqlite3_backup_step(). The user is required to ensure that no
** other thread accesses the destination handle for the duration
** of the backup operation. Any attempt to use the destination
** database connection while a backup is in progress may cause
** a malfunction or a deadlock.
*/
sqlite3_mutex_enter(pSrcDb->mutex);
sqlite3_mutex_enter(pDestDb->mutex);
if( pSrcDb==pDestDb ){
/* If there is no open read-transaction on the source database, open
** one now. If a transaction is opened here, then it will be closed
** before this function exits.
*/
if( rc==SQLITE_OK && SQLITE_TXN_NONE==sqlite3BtreeTxnState(p->pSrc) ){
rc = sqlite3BtreeBeginTrans(p->pSrc, 0, 0);
bCloseTrans = 1;
}
/* If the destination database has not yet been locked (i.e. if this
** is the first call to backup_step() for the current backup operation),
** try to set its page size to the same as the source database. This
** is especially important on ZipVFS systems, as in that case it is
** not possible to create a database file that uses one page size by
** writing to it with another. */
if( p->bDestLocked==0 && rc==SQLITE_OK && setDestPgsz(p)==SQLITE_NOMEM ){
rc = SQLITE_NOMEM;
}
/* Lock the destination database, if it is not locked already. */
if( SQLITE_OK==rc && p->bDestLocked==0
&& SQLITE_OK==(rc = sqlite3BtreeBeginTrans(p->pDest, 2,
(int*)&p->iDestSchema))
){
p->bDestLocked = 1;
}
/* Do not allow backup if the destination database is in WAL mode
** and the page sizes are different between source and destination */
pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
for(i=0; i<nDb; i++){
if( i!=1 && DbMaskTest(p->lockMask,i) && ALWAYS(aDb[i].pBt!=0) ){
sqlite3BtreeEnter(aDb[i].pBt);
}
}
}
#endif
#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
/*
** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
*/
static SQLITE_NOINLINE void vdbeLeave(Vdbe *p){
int i;
sqlite3 *db;
Db *aDb;
int nDb;
db = p->db;
aDb = db->aDb;
nDb = db->nDb;
for(i=0; i<nDb; i++){
assert( db->nVdbeActive>=db->nVdbeRead );
assert( db->nVdbeRead>=db->nVdbeWrite );
assert( db->nVdbeWrite>=0 );
p->eVdbeState = VDBE_HALT_STATE;
checkActiveVdbeCnt(db);
if( db->mallocFailed ){
p->rc = SQLITE_NOMEM_BKPT;
}
/* If the auto-commit flag is set to true, then any locks that were held
** by connection db have now been released. Call sqlite3ConnectionUnlocked()
** to invoke any required unlock-notify callbacks.
*/
if( db->autoCommit ){
sqlite3ConnectionUnlocked(db);
}
assert( db->nVdbeActive>0 || db->autoCommit==0 || db->nStatement==0 );
return (p->rc==SQLITE_BUSY ? SQLITE_BUSY : SQLITE_OK);
}
/*
** Each VDBE holds the result of the most recent sqlite3_step() call
** in p->rc. This routine sets that result back to SQLITE_OK.
**
** Obtain a lock on a particular table. This instruction is only used when
** the shared-cache feature is enabled.
**
** P1 is the index of the database in sqlite3.aDb[] of the database
** on which the lock is acquired. A readlock is obtained if P3==0 or
** a write lock if P3==1.
**
** P2 contains the root-page of the table to lock.
**
** P4 contains a pointer to the name of the table being locked. This is only
** used to generate an error message if the lock cannot be obtained.
*/
case OP_TableLock: {
u8 isWriteLock = (u8)pOp->p3;
if( isWriteLock || 0==(db->flags&SQLITE_ReadUncommit) ){
int p1 = pOp->p1;
assert( p1>=0 && p1<db->nDb );
assert( DbMaskTest(p->btreeMask, p1) );
assert( isWriteLock==0 || isWriteLock==1 );
rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
if( rc ){
if( (rc&0xFF)==SQLITE_LOCKED ){
const char *z = pOp->p4.z;
sqlite3VdbeError(p, "database table is locked: %s", z);
}
goto abort_due_to_error;
}
}
break;
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Opcode: VBegin * * * P4 *
SortSubtask *pTask,
const char *zEvent
){
i64 t;
int iTask = (pTask - pTask->pSorter->aTask);
sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
fprintf(stderr, "%lld:bg%d %s\n", t, iTask, zEvent);
}
static void vdbeSorterBlockDebug(
SortSubtask *pTask,
int bBlocked,
const char *zEvent
){
if( bBlocked ){
i64 t;
sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
fprintf(stderr, "%lld:main %s\n", t, zEvent);
}
}
#else
# define vdbeSorterWorkDebug(x,y)
# define vdbeSorterRewindDebug(y)
# define vdbeSorterPopulateDebug(x,y)
# define vdbeSorterBlockDebug(x,y,z)
sqlite3_snprintf(sizeof(zErr),zErr, "no such database: %s", zName);
goto detach_error;
}
if( i<2 ){
sqlite3_snprintf(sizeof(zErr),zErr, "cannot detach database %s", zName);
goto detach_error;
}
if( sqlite3BtreeTxnState(pDb->pBt)!=SQLITE_TXN_NONE
|| sqlite3BtreeIsInBackup(pDb->pBt)
){
sqlite3_snprintf(sizeof(zErr),zErr, "database %s is locked", zName);
goto detach_error;
}
/* If any TEMP triggers reference the schema being detached, move those
** triggers to reference the TEMP schema itself. */
assert( db->aDb[1].pSchema );
pEntry = sqliteHashFirst(&db->aDb[1].pSchema->trigHash);
while( pEntry ){
Trigger *pTrig = (Trigger*)sqliteHashData(pEntry);
if( pTrig->pTabSchema==pDb->pSchema ){
** ROLLBACK
*/
/* #include "sqliteInt.h" */
#ifndef SQLITE_OMIT_SHARED_CACHE
/*
** The TableLock structure is only used by the sqlite3TableLock() and
** codeTableLocks() functions.
*/
struct TableLock {
int iDb; /* The database containing the table to be locked */
Pgno iTab; /* The root page of the table to be locked */
u8 isWriteLock; /* True for write lock. False for a read lock */
const char *zLockName; /* Name of the table */
};
/*
** Record the fact that we want to lock a table at run-time.
**
** The table to be locked has root page iTab and is found in database iDb.
** A read or a write lock can be taken depending on isWritelock.
**
** This routine just records the fact that the lock is desired. The
** code to make the lock occur is generated by a later call to
** codeTableLocks() which occurs during sqlite3FinishCoding().
*/
static SQLITE_NOINLINE void lockTable(
Parse *pParse, /* Parsing context */
int iDb, /* Index of the database containing the table to lock */
Pgno iTab, /* Root page number of the table to be locked */
u8 isWriteLock, /* True for a write lock */
const char *zName /* Name of the table to be locked */
){
Parse *pToplevel;
int i;
int nBytes;
TableLock *p;
assert( iDb>=0 );
pToplevel = sqlite3ParseToplevel(pParse);
for(i=0; i<pToplevel->nTableLock; i++){
p = &pToplevel->aTableLock[i];
p->isWriteLock = isWriteLock;
p->zLockName = zName;
}else{
pToplevel->nTableLock = 0;
sqlite3OomFault(pToplevel->db);
}
}
SQLITE_PRIVATE void sqlite3TableLock(
Parse *pParse, /* Parsing context */
int iDb, /* Index of the database containing the table to lock */
Pgno iTab, /* Root page number of the table to be locked */
u8 isWriteLock, /* True for a write lock */
const char *zName /* Name of the table to be locked */
){
if( iDb==1 ) return;
if( !sqlite3BtreeSharable(pParse->db->aDb[iDb].pBt) ) return;
lockTable(pParse, iDb, iTab, isWriteLock, zName);
}
/*
** Code an OP_TableLock instruction for each table locked by the
** statement (configured by calls to sqlite3TableLock()).
*/
static void codeTableLocks(Parse *pParse){
int i;
Vdbe *pVdbe = pParse->pVdbe;
assert( pVdbe!=0 );
for(i=0; i<pParse->nTableLock; i++){
TableLock *p = &pParse->aTableLock[i];
int p1 = p->iDb;
returnSingleInt(v, db->nAnalysisLimit); /* IMP: R-57594-65522 */
break;
}
#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
/*
** Report the current state of file logs for all databases
*/
case PragTyp_LOCK_STATUS: {
static const char *const azLockName[] = {
"unlocked", "shared", "reserved", "pending", "exclusive"
};
int i;
pParse->nMem = 2;
for(i=0; i<db->nDb; i++){
Btree *pBt;
const char *zState = "unknown";
int j;
if( db->aDb[i].zDbSName==0 ) continue;
pBt = db->aDb[i].pBt;
if( pBt==0 || sqlite3BtreePager(pBt)==0 ){
** works even if READ_UNCOMMITTED is set.
*/
if( !db->noSharedCache ){
for(i=0; i<db->nDb; i++) {
Btree *pBt = db->aDb[i].pBt;
if( pBt ){
assert( sqlite3BtreeHoldsMutex(pBt) );
rc = sqlite3BtreeSchemaLocked(pBt);
if( rc ){
const char *zDb = db->aDb[i].zDbSName;
sqlite3ErrorWithMsg(db, rc, "database schema is locked: %s", zDb);
testcase( db->flags & SQLITE_ReadUncommit );
goto end_prepare;
}
}
}
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( db->pDisconnect ) sqlite3VtabUnlockList(db);
#endif
assert( rc==SQLITE_OK || (*ppStmt)==0 );
return rc;
}
/*
** Rerun the compilation of a statement after a schema change.
**
** If the statement is successfully recompiled, return SQLITE_OK. Otherwise,
** if the statement cannot be recompiled because another connection has
** locked the sqlite3_schema table, return SQLITE_LOCKED. If any other error
** occurs, return SQLITE_SCHEMA.
*/
SQLITE_PRIVATE int sqlite3Reprepare(Vdbe *p){
int rc;
sqlite3_stmt *pNew;
const char *zSql;
sqlite3 *db;
u8 prepFlags;
assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );
return 0;
}
isOuterJoin = 1;
}
assert( pSubSrc->nSrc>0 ); /* True by restriction (7) */
if( iFrom>0 && (pSubSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
return 0; /* Restriction (27a) */
}
/* Condition (28) is blocked by the caller */
assert( !pSubitem->fg.isCte || pSubitem->u2.pCteUse->eM10d!=M10d_Yes );
/* Restriction (17): If the sub-query is a compound SELECT, then it must
** use only the UNION ALL operator. And none of the simple select queries
** that make up the compound SELECT are allowed to be aggregate or distinct
** queries.
*/
if( pSub->pPrior ){
int ii;
if( pSub->pOrderBy ){
assert( pMod->pEpoTab==0 );
sqlite3DbFree(db, pMod);
}
}
/*
** Lock the virtual table so that it cannot be disconnected.
** Locks nest. Every lock should have a corresponding unlock.
** If an unlock is omitted, resources leaks will occur.
**
** If a disconnect is attempted while a virtual table is locked,
** the disconnect is deferred until all locks have been removed.
*/
SQLITE_PRIVATE void sqlite3VtabLock(VTable *pVTab){
pVTab->nRef++;
}
/*
** pTab is a pointer to a Table structure representing a virtual-table.
** Return a pointer to the VTable object used by connection db to access
** Return a static string that describes the kind of error specified in the
** argument.
*/
SQLITE_PRIVATE const char *sqlite3ErrStr(int rc){
static const char* const aMsg[] = {
/* SQLITE_OK */ "not an error",
/* SQLITE_ERROR */ "SQL logic error",
/* SQLITE_INTERNAL */ 0,
/* SQLITE_PERM */ "access permission denied",
/* SQLITE_ABORT */ "query aborted",
/* SQLITE_BUSY */ "database is locked",
/* SQLITE_LOCKED */ "database table is locked",
/* SQLITE_NOMEM */ "out of memory",
/* SQLITE_READONLY */ "attempt to write a readonly database",
/* SQLITE_INTERRUPT */ "interrupted",
/* SQLITE_IOERR */ "disk I/O error",
/* SQLITE_CORRUPT */ "database disk image is malformed",
/* SQLITE_NOTFOUND */ "unknown operation",
/* SQLITE_FULL */ "database or disk is full",
/* SQLITE_CANTOPEN */ "unable to open database file",
/* SQLITE_PROTOCOL */ "locking protocol",
/* SQLITE_EMPTY */ 0,
*/
/* #include "sqliteInt.h" */
/* #include "btreeInt.h" */
/* Omit this entire file if SQLITE_ENABLE_UNLOCK_NOTIFY is not defined. */
#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
/*
** Public interfaces:
**
** sqlite3ConnectionBlocked()
** sqlite3ConnectionUnlocked()
** sqlite3ConnectionClosed()
** sqlite3_unlock_notify()
*/
#define assertMutexHeld() \
assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN)) )
/*
** Head of a linked list of all sqlite3 objects created by this process
** for which either sqlite3.pBlockingConnection or sqlite3.pUnlockConnection
** is not NULL. This variable may only accessed while the STATIC_MAIN
** mutex is held.
*/
static sqlite3 *SQLITE_WSD sqlite3BlockedList = 0;
#ifndef NDEBUG
/*
** This function is a complex assert() that verifies the following
** properties of the blocked connections list:
**
** 1) Each entry in the list has a non-NULL value for either
** pUnlockConnection or pBlockingConnection, or both.
**
** 2) All entries in the list that share a common value for
** xUnlockNotify are grouped together.
**
** 3) If the argument db is not NULL, then none of the entries in the
** blocked connections list have pUnlockConnection or pBlockingConnection
** set to db. This is used when closing connection db.
*/
static void checkListProperties(sqlite3 *db){
sqlite3 *p;
for(p=sqlite3BlockedList; p; p=p->pNextBlocked){
int seen = 0;
sqlite3 *p2;
/* Verify property (1) */
assert( p->pUnlockConnection || p->pBlockingConnection );
/* Verify property (2) */
for(p2=sqlite3BlockedList; p2!=p; p2=p2->pNextBlocked){
if( p2->xUnlockNotify==p->xUnlockNotify ) seen = 1;
assert( p2->xUnlockNotify==p->xUnlockNotify || !seen );
assert( db==0 || p->pUnlockConnection!=db );
assert( db==0 || p->pBlockingConnection!=db );
}
}
}
#else
# define checkListProperties(x)
#endif
/*
** Remove connection db from the blocked connections list. If connection
** db is not currently a part of the list, this function is a no-op.
*/
static void removeFromBlockedList(sqlite3 *db){
sqlite3 **pp;
assertMutexHeld();
for(pp=&sqlite3BlockedList; *pp; pp = &(*pp)->pNextBlocked){
if( *pp==db ){
*pp = (*pp)->pNextBlocked;
break;
}
}
}
/*
** Add connection db to the blocked connections list. It is assumed
** that it is not already a part of the list.
*/
static void addToBlockedList(sqlite3 *db){
sqlite3 **pp;
assertMutexHeld();
for(
pp=&sqlite3BlockedList;
*pp && (*pp)->xUnlockNotify!=db->xUnlockNotify;
pp=&(*pp)->pNextBlocked
);
db->pNextBlocked = *pp;
*pp = db;
}
/*
** Obtain the STATIC_MAIN mutex.
*/
static void enterMutex(void){
sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MAIN));
checkListProperties(0);
}
** Register an unlock-notify callback.
**
** This is called after connection "db" has attempted some operation
** but has received an SQLITE_LOCKED error because another connection
** (call it pOther) in the same process was busy using the same shared
** cache. pOther is found by looking at db->pBlockingConnection.
**
** If there is no blocking connection, the callback is invoked immediately,
** before this routine returns.
**
** If pOther is already blocked on db, then report SQLITE_LOCKED, to indicate
** a deadlock.
**
** Otherwise, make arrangements to invoke xNotify when pOther drops
** its locks.
**
** Each call to this routine overrides any prior callbacks registered
** on the same "db". If xNotify==0 then any prior callbacks are immediately
** cancelled.
*/
SQLITE_API int sqlite3_unlock_notify(
){
int rc = SQLITE_OK;
#ifdef SQLITE_ENABLE_API_ARMOR
if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
#endif
sqlite3_mutex_enter(db->mutex);
enterMutex();
if( xNotify==0 ){
removeFromBlockedList(db);
db->pBlockingConnection = 0;
db->pUnlockConnection = 0;
db->xUnlockNotify = 0;
db->pUnlockArg = 0;
}else if( 0==db->pBlockingConnection ){
/* The blocking transaction has been concluded. Or there never was a
** blocking transaction. In either case, invoke the notify callback
** immediately.
*/
xNotify(&pArg, 1);
}else{
sqlite3 *p;
for(p=db->pBlockingConnection; p && p!=db; p=p->pUnlockConnection){}
if( p ){
rc = SQLITE_LOCKED; /* Deadlock detected. */
}else{
db->pUnlockConnection = db->pBlockingConnection;
db->xUnlockNotify = xNotify;
db->pUnlockArg = pArg;
removeFromBlockedList(db);
addToBlockedList(db);
}
}
leaveMutex();
assert( !db->mallocFailed );
sqlite3ErrorWithMsg(db, rc, (rc?"database is deadlocked":0));
sqlite3_mutex_leave(db->mutex);
return rc;
}
/*
** This function is called while stepping or preparing a statement
** associated with connection db. The operation will return SQLITE_LOCKED
** to the user because it requires a lock that will not be available
** until connection pBlocker concludes its current transaction.
*/
SQLITE_PRIVATE void sqlite3ConnectionBlocked(sqlite3 *db, sqlite3 *pBlocker){
enterMutex();
if( db->pBlockingConnection==0 && db->pUnlockConnection==0 ){
addToBlockedList(db);
}
db->pBlockingConnection = pBlocker;
leaveMutex();
}
/*
** This function is called when
** the transaction opened by database db has just finished. Locks held
** by database connection db have been released.
**
** This function loops through each entry in the blocked connections
** list and does the following:
**
** 1) If the sqlite3.pBlockingConnection member of a list entry is
** set to db, then set pBlockingConnection=0.
**
** 2) If the sqlite3.pUnlockConnection member of a list entry is
** set to db, then invoke the configured unlock-notify callback and
** set pUnlockConnection=0.
**
** 3) If the two steps above mean that pBlockingConnection==0 and
** pUnlockConnection==0, remove the entry from the blocked connections
** list.
*/
SQLITE_PRIVATE void sqlite3ConnectionUnlocked(sqlite3 *db){
void (*xUnlockNotify)(void **, int) = 0; /* Unlock-notify cb to invoke */
int nArg = 0; /* Number of entries in aArg[] */
sqlite3 **pp; /* Iterator variable */
void **aArg; /* Arguments to the unlock callback */
void **aDyn = 0; /* Dynamically allocated space for aArg[] */
void *aStatic[16]; /* Starter space for aArg[]. No malloc required */
aArg = aStatic;
enterMutex(); /* Enter STATIC_MAIN mutex */
/* This loop runs once for each entry in the blocked-connections list. */
for(pp=&sqlite3BlockedList; *pp; /* no-op */ ){
sqlite3 *p = *pp;
/* Step 1. */
if( p->pBlockingConnection==db ){
p->pBlockingConnection = 0;
}
/* Step 2. */
if( p->pUnlockConnection==db ){
assert( p->xUnlockNotify );
aDyn = aArg = pNew;
}else{
/* This occurs when the array of context pointers that need to
** be passed to the unlock-notify callback is larger than the
** aStatic[] array allocated on the stack and the attempt to
** allocate a larger array from the heap has failed.
**
** This is a difficult situation to handle. Returning an error
** code to the caller is insufficient, as even if an error code
** is returned the transaction on connection db will still be
** closed and the unlock-notify callbacks on blocked connections
** will go unissued. This might cause the application to wait
** indefinitely for an unlock-notify callback that will never
** arrive.
**
** Instead, invoke the unlock-notify callback with the context
** array already accumulated. We can then clear the array and
** begin accumulating any further context pointers without
** requiring any dynamic allocation. This is sub-optimal because
** it means that instead of one callback with a large array of
** context pointers the application will receive two or more
aArg[nArg++] = p->pUnlockArg;
xUnlockNotify = p->xUnlockNotify;
p->pUnlockConnection = 0;
p->xUnlockNotify = 0;
p->pUnlockArg = 0;
}
/* Step 3. */
if( p->pBlockingConnection==0 && p->pUnlockConnection==0 ){
/* Remove connection p from the blocked connections list. */
*pp = p->pNextBlocked;
p->pNextBlocked = 0;
}else{
pp = &p->pNextBlocked;
}
}
if( nArg!=0 ){
xUnlockNotify(aArg, nArg);
}
sqlite3_free(aDyn);
leaveMutex(); /* Leave STATIC_MAIN mutex */
}
/*
** This is called when the database connection passed as an argument is
** being closed. The connection is removed from the blocked list.
*/
SQLITE_PRIVATE void sqlite3ConnectionClosed(sqlite3 *db){
sqlite3ConnectionUnlocked(db);
enterMutex();
removeFromBlockedList(db);
checkListProperties(db);
leaveMutex();
}
#endif
/************** End of notify.c **********************************************/
/************** Begin file fts3.c ********************************************/
/*
** 2006 Oct 10
**
** New error codes may be added in future versions of SQLite.
**
** See also: [extended result code definitions]
*/
#define SQLITE_OK 0 /* Successful result */
/* beginning-of-error-codes */
#define SQLITE_ERROR 1 /* Generic error */
#define SQLITE_INTERNAL 2 /* Internal logic error in SQLite */
#define SQLITE_PERM 3 /* Access permission denied */
#define SQLITE_ABORT 4 /* Callback routine requested an abort */
#define SQLITE_BUSY 5 /* The database file is locked */
#define SQLITE_LOCKED 6 /* A table in the database is locked */
#define SQLITE_NOMEM 7 /* A malloc() failed */
#define SQLITE_READONLY 8 /* Attempt to write a readonly database */
#define SQLITE_INTERRUPT 9 /* Operation terminated by sqlite3_interrupt()*/
#define SQLITE_IOERR 10 /* Some kind of disk I/O error occurred */
#define SQLITE_CORRUPT 11 /* The database disk image is malformed */
#define SQLITE_NOTFOUND 12 /* Unknown opcode in sqlite3_file_control() */
#define SQLITE_FULL 13 /* Insertion failed because database is full */
#define SQLITE_CANTOPEN 14 /* Unable to open the database file */
#define SQLITE_PROTOCOL 15 /* Database lock protocol error */
#define SQLITE_EMPTY 16 /* Internal use only */
** this file-control is NULL. However, if the database file is being synced
** as part of a multi-database commit, the argument points to a nul-terminated
** string containing the transactions super-journal file name. VFSes that
** do not need this signal should silently ignore this opcode. Applications
** should not call [sqlite3_file_control()] with this opcode as doing so may
** disrupt the operation of the specialized VFSes that do require it.
**
** <li>[[SQLITE_FCNTL_COMMIT_PHASETWO]]
** The [SQLITE_FCNTL_COMMIT_PHASETWO] opcode is generated internally by SQLite
** and sent to the VFS after a transaction has been committed immediately
** but before the database is unlocked. VFSes that do not need this signal
** should silently ignore this opcode. Applications should not call
** [sqlite3_file_control()] with this opcode as doing so may disrupt the
** operation of the specialized VFSes that do require it.
**
** <li>[[SQLITE_FCNTL_WIN32_AV_RETRY]]
** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
** retry counts and intervals for certain disk I/O operations for the
** windows [VFS] in order to provide robustness in the presence of
** anti-virus programs. By default, the windows VFS will retry file read,
** file write, and file delete operations up to 10 times, with a delay
** <ul>
** <li> SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
** <li> SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
** <li> SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
** <li> SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
** </ul>
**
** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
** was given on the corresponding lock.
**
** The xShmLock method can transition between unlocked and SHARED or
** between unlocked and EXCLUSIVE. It cannot transition between SHARED
** and EXCLUSIVE.
*/
#define SQLITE_SHM_UNLOCK 1
#define SQLITE_SHM_LOCK 2
#define SQLITE_SHM_SHARED 4
#define SQLITE_SHM_EXCLUSIVE 8
/*
** CAPI3REF: Maximum xShmLock index
**
/*
** CAPI3REF: Register A Callback To Handle SQLITE_BUSY Errors
** KEYWORDS: {busy-handler callback} {busy handler}
** METHOD: sqlite3
**
** ^The sqlite3_busy_handler(D,X,P) routine sets a callback function X
** that might be invoked with argument P whenever
** an attempt is made to access a database table associated with
** [database connection] D when another thread
** or process has the table locked.
** The sqlite3_busy_handler() interface is used to implement
** [sqlite3_busy_timeout()] and [PRAGMA busy_timeout].
**
** ^If the busy callback is NULL, then [SQLITE_BUSY]
** is returned immediately upon encountering the lock. ^If the busy callback
** is not NULL, then the callback might be invoked with two arguments.
**
** ^The first argument to the busy handler is a copy of the void* pointer which
** is the third argument to sqlite3_busy_handler(). ^The second argument to
** the busy handler callback is the number of times that the busy handler has
**
** The presence of a busy handler does not guarantee that it will be invoked
** when there is lock contention. ^If SQLite determines that invoking the busy
** handler could result in a deadlock, it will go ahead and return [SQLITE_BUSY]
** to the application instead of invoking the
** busy handler.
** Consider a scenario where one process is holding a read lock that
** it is trying to promote to a reserved lock and
** a second process is holding a reserved lock that it is trying
** to promote to an exclusive lock. The first process cannot proceed
** because it is blocked by the second and the second process cannot
** proceed because it is blocked by the first. If both processes
** invoke the busy handlers, neither will make any progress. Therefore,
** SQLite returns [SQLITE_BUSY] for the first process, hoping that this
** will induce the first process to release its read lock and allow
** the second process to proceed.
**
** ^The default busy callback is NULL.
**
** ^(There can only be a single busy handler defined for each
** [database connection]. Setting a new busy handler clears any
** previously set handler.)^ ^Note that calling [sqlite3_busy_timeout()]
** A busy handler must not close the database connection
** or [prepared statement] that invoked the busy handler.
*/
SQLITE_API int sqlite3_busy_handler(sqlite3*,int(*)(void*,int),void*);
/*
** CAPI3REF: Set A Busy Timeout
** METHOD: sqlite3
**
** ^This routine sets a [sqlite3_busy_handler | busy handler] that sleeps
** for a specified amount of time when a table is locked. ^The handler
** will sleep multiple times until at least "ms" milliseconds of sleeping
** have accumulated. ^After at least "ms" milliseconds of sleeping,
** the handler returns 0 which causes [sqlite3_step()] to return
** [SQLITE_BUSY].
**
** ^Calling this routine with an argument less than or equal to zero
** turns off all busy handlers.
**
** ^(There can only be a single busy handler for a particular
** [database connection] at any given moment. If another busy handler
** CAPI3REF: Online Backup API.
**
** The backup API copies the content of one database into another.
** It is useful either for creating backups of databases or
** for copying in-memory databases to or from persistent files.
**
** See Also: [Using the SQLite Online Backup API]
**
** ^SQLite holds a write transaction open on the destination database file
** for the duration of the backup operation.
** ^The source database is read-locked only while it is being read;
** it is not locked continuously for the entire backup operation.
** ^Thus, the backup may be performed on a live source database without
** preventing other database connections from
** reading or writing to the source database while the backup is underway.
**
** ^(To perform a backup operation:
** <ol>
** <li><b>sqlite3_backup_init()</b> is called once to initialize the
** backup,
** <li><b>sqlite3_backup_step()</b> is called one or more times to transfer
** the data between the two databases, and finally
** errors are considered fatal.)^ The application must accept
** that the backup operation has failed and pass the backup operation handle
** to the sqlite3_backup_finish() to release associated resources.
**
** ^The first call to sqlite3_backup_step() obtains an exclusive lock
** on the destination file. ^The exclusive lock is not released until either
** sqlite3_backup_finish() is called or the backup operation is complete
** and sqlite3_backup_step() returns [SQLITE_DONE]. ^Every call to
** sqlite3_backup_step() obtains a [shared lock] on the source database that
** lasts for the duration of the sqlite3_backup_step() call.
** ^Because the source database is not locked between calls to
** sqlite3_backup_step(), the source database may be modified mid-way
** through the backup process. ^If the source database is modified by an
** external process or via a database connection other than the one being
** used by the backup operation, then the backup will be automatically
** restarted by the next call to sqlite3_backup_step(). ^If the source
** database is modified by the using the same database connection as is used
** by the backup operation, then the backup database is automatically
** updated at the same time.
**
** [[sqlite3_backup_finish()]] <b>sqlite3_backup_finish()</b>
** ^This API may be used to register a callback that SQLite will invoke
** when the connection currently holding the required lock relinquishes it.
** ^This API is only available if the library was compiled with the
** [SQLITE_ENABLE_UNLOCK_NOTIFY] C-preprocessor symbol defined.
**
** See Also: [Using the SQLite Unlock Notification Feature].
**
** ^Shared-cache locks are released when a database connection concludes
** its current transaction, either by committing it or rolling it back.
**
** ^When a connection (known as the blocked connection) fails to obtain a
** shared-cache lock and SQLITE_LOCKED is returned to the caller, the
** identity of the database connection (the blocking connection) that
** has locked the required resource is stored internally. ^After an
** application receives an SQLITE_LOCKED error, it may call the
** sqlite3_unlock_notify() method with the blocked connection handle as
** the first argument to register for a callback that will be invoked
** when the blocking connections current transaction is concluded. ^The
** callback is invoked from within the [sqlite3_step] or [sqlite3_close]
** call that concludes the blocking connection's transaction.
**
** ^(If sqlite3_unlock_notify() is called in a multi-threaded application,
** there is a chance that the blocking connection will have already
** concluded its transaction by the time sqlite3_unlock_notify() is invoked.
** If this happens, then the specified callback is invoked immediately,
** from within the call to sqlite3_unlock_notify().)^
**
** ^If the blocked connection is attempting to obtain a write-lock on a
** shared-cache table, and more than one other connection currently holds
** a read-lock on the same table, then SQLite arbitrarily selects one of
** the other connections to use as the blocking connection.
**
** ^(There may be at most one unlock-notify callback registered by a
** blocked connection. If sqlite3_unlock_notify() is called when the
** blocked connection already has a registered unlock-notify callback,
** then the new callback replaces the old.)^ ^If sqlite3_unlock_notify() is
** called with a NULL pointer as its second argument, then any existing
** unlock-notify callback is canceled. ^The blocked connections
** unlock-notify callback may also be canceled by closing the blocked
** connection using [sqlite3_close()].
**
** The unlock-notify callback is not reentrant. If an application invokes
** any sqlite3_xxx API functions from within an unlock-notify callback, a
** crash or deadlock may be the result.
**
** ^Unless deadlock is detected (see below), sqlite3_unlock_notify() always
** returns SQLITE_OK.
**
** <b>Callback Invocation Details</b>
**
** When an unlock-notify callback is registered, the application provides a
** single void* pointer that is passed to the callback when it is invoked.
** However, the signature of the callback function allows SQLite to pass
** it an array of void* context pointers. The first argument passed to
** an unlock-notify callback is a pointer to an array of void* pointers,
** and the second is the number of entries in the array.
**
** When a blocking connection's transaction is concluded, there may be
** more than one blocked connection that has registered for an unlock-notify
** callback. ^If two or more such blocked connections have specified the
** same callback function, then instead of invoking the callback function
** multiple times, it is invoked once with the set of void* context pointers
** specified by the blocked connections bundled together into an array.
** This gives the application an opportunity to prioritize any actions
** related to the set of unblocked database connections.
**
** <b>Deadlock Detection</b>
**
** Assuming that after registering for an unlock-notify callback a
** database waits for the callback to be issued before taking any further
** action (a reasonable assumption), then using this API may cause the
** application to deadlock. For example, if connection X is waiting for
** connection Y's transaction to be concluded, and similarly connection
** Y is waiting on connection X's transaction, then neither connection
** will proceed and the system may remain deadlocked indefinitely.
**
** To avoid this scenario, the sqlite3_unlock_notify() performs deadlock
** detection. ^If a given call to sqlite3_unlock_notify() would put the
** system in a deadlocked state, then SQLITE_LOCKED is returned and no
** unlock-notify callback is registered. The system is said to be in
** a deadlocked state if connection A has registered for an unlock-notify
** callback on the conclusion of connection B's transaction, and connection
** B has itself registered for an unlock-notify callback when connection
** A's transaction is concluded. ^Indirect deadlock is also detected, so
** the system is also considered to be deadlocked if connection B has
** registered for an unlock-notify callback on the conclusion of connection
** C's transaction, where connection C is waiting on connection A. ^Any
** number of levels of indirection are allowed.
**
** <b>The "DROP TABLE" Exception</b>
**
** When a call to [sqlite3_step()] returns SQLITE_LOCKED, it is almost
** always appropriate to call sqlite3_unlock_notify(). There is however,
** one exception. When executing a "DROP TABLE" or "DROP INDEX" statement,
** SQLite checks if there are any currently executing SELECT statements
** invoked immediately. If the application then re-attempts the "DROP TABLE"
** or "DROP INDEX" query, an infinite loop might be the result.
**
** One way around this problem is to check the extended error code returned
** by an sqlite3_step() call. ^(If there is a blocking connection, then the
** extended error code is set to SQLITE_LOCKED_SHAREDCACHE. Otherwise, in
** the special "DROP TABLE/INDEX" case, the extended error code is just
** SQLITE_LOCKED.)^
*/
SQLITE_API int sqlite3_unlock_notify(
sqlite3 *pBlocked, /* Waiting connection */
void (*xNotify)(void **apArg, int nArg), /* Callback function to invoke */
void *pNotifyArg /* Argument to pass to xNotify */
);
/*
** CAPI3REF: String Comparison
**
** ^The [sqlite3_stricmp()] and [sqlite3_strnicmp()] APIs allow applications
** and extensions to compare the contents of two buffers containing UTF-8
t/08_busy.t view on Meta::CPAN
dbfile => 'foo',
RaiseError => 1,
PrintError => 0,
AutoCommit => 0,
);
my $dbfile = dbfile('foo');
# NOTE: Let's make it clear what we're doing here.
# $dbh starts locking with the first INSERT statement.
# $dbh2 tries to INSERT, but as the database is locked,
# it starts waiting. However, $dbh won't release the lock.
# Eventually $dbh2 gets timed out, and spits an error, saying
# the database is locked. So, we don't need to let $dbh2 wait
# too much here. It should be timed out anyway.
ok($dbh2->$call_func(300, 'busy_timeout'));
ok($dbh->do("CREATE TABLE Blah ( id INTEGER, val VARCHAR )"));
ok($dbh->commit);
ok($dbh->do("INSERT INTO Blah VALUES ( 1, 'Test1' )"));
eval {
$dbh2->do("INSERT INTO Blah VALUES ( 2, 'Test2' )");
};
ok($@);
t/08_busy.t view on Meta::CPAN
$dbh->commit;
ok($dbh2->do("INSERT INTO Blah VALUES ( 2, 'Test2' )"));
$dbh2->commit;
$dbh2->disconnect;
undef($dbh2);
# NOTE: The second test is to see what happens if a lock is
# is released while waiting. When both parent and child are
# ready, the database is locked by the child. The parent
# starts waiting for a long enough time (apparently we need
# to wait much longer than we expected, as testers may use
# very slow (virtual) machines to test, but don't worry,
# it's only for the slowest environment). After a short sleep,
# the child commits and releases the lock. Eventually the parent
# notices that, and does the pended INSERT (hopefully before
# it is timed out). As both the parent and the child wait till
# both are ready, we don't need to sleep for a long time.
pipe(READER, WRITER);
my $pid = fork;
t/47_execute.t view on Meta::CPAN
dbfile => 'foo',
RaiseError => 1,
PrintError => 0,
AutoCommit => 0,
);
my $dbfile = dbfile('foo');
# NOTE: Let's make it clear what we're doing here.
# $dbh starts locking with the first INSERT statement.
# $dbh2 tries to INSERT, but as the database is locked,
# it starts waiting. However, $dbh won't release the lock.
# Eventually $dbh2 gets timed out, and spits an error, saying
# the database is locked. So, we don't need to let $dbh2 wait
# too much here. It should be timed out anyway.
ok($dbh->$call_func(300, 'busy_timeout'));
ok($dbh2->$call_func(300, 'busy_timeout'));
$dbh->do("CREATE TABLE Blah ( id INTEGER )");
$dbh->do("INSERT INTO Blah VALUES ( 1 )");
$dbh->commit;
my $sth;
ok($sth = $dbh->prepare("SELECT id FROM Blah"));
$sth->execute;
( run in 0.566 second using v1.01-cache-2.11-cpan-49f99fa48dc )