/*
* Create a shared memory segment of the given size and initialize. Also,
* register an on_shmem_exit callback to release the storage.
*/
void *
pool_shared_memory_create(size_t size)
{
int shmid;
void *memAddress;
/* Try to create new segment */
shmid = shmget(IPC_PRIVATE, size, IPC_CREAT | IPC_EXCL | IPCProtection);
if (shmid < 0)
{
pool_error("could not create shared memory segment: %s",
strerror(errno));
return NULL;
}
/* Register on-exit routine to delete the new segment */
on_shmem_exit(IpcMemoryDelete, shmid);
/* OK, should be able to attach to the segment */
memAddress = shmat(shmid, NULL, PG_SHMAT_FLAGS);
if (memAddress == (void *) -1)
{
pool_error("shmat(id=%d) failed: %s", shmid, strerror(errno));
return NULL;
}
/* Register on-exit routine to detach new segment before deleting */
on_shmem_exit(IpcMemoryDetach, (Datum) memAddress);
return memAddress;
}
/*
* ProcSignalInit
* Register the current process in the procsignal array
*
* The passed index should be my BackendId if the process has one,
* or MaxBackends + aux process type if not.
*/
void
ProcSignalInit(int pss_idx)
{
volatile ProcSignalSlot *slot;
Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);
slot = &ProcSignalSlots[pss_idx - 1];
/* sanity check */
if (slot->pss_pid != 0)
elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
MyProcPid, pss_idx);
/* Clear out any leftover signal reasons */
MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
/* Mark slot with my PID */
slot->pss_pid = MyProcPid;
/* Remember slot location for CheckProcSignal */
MyProcSignalSlot = slot;
/* Set up to release the slot on process exit */
on_shmem_exit(CleanupProcSignalState, Int32GetDatum(pss_idx));
}
/*
* Create a semaphore set and initialize.
*/
void
pool_semaphore_create(int numSems)
{
int i;
/* Try to create new semaphore set */
semId = semget(IPC_PRIVATE, numSems, IPC_CREAT | IPC_EXCL | IPCProtection);
if (semId < 0)
ereport(FATAL,
(errmsg("Unable to create semaphores:%d error:\"%s\"",numSems,strerror(errno))));
on_shmem_exit(IpcSemaphoreKill, semId);
/* Initialize it to count 1 */
for (i = 0; i < numSems; i++)
{
union semun semun;
semun.val = 1;
if (semctl(semId, i, SETVAL, semun) < 0)
ereport(FATAL,
(errmsg("Unable to create semaphores:%d error:\"%s\"",numSems,strerror(errno)),
errdetail("semctl(%d, %d, SETVAL, %d) failed",semId,i,semun.val)));
}
}
/*
* SIBackendInit
* Initialize a new backend to operate on the sinval buffer
*
* Returns:
* >0 A-OK
* 0 Failed to find a free procState slot (ie, MaxBackends exceeded)
* <0 Some other failure (not currently used)
*
* NB: this routine, and all following ones, must be executed with the
* SInvalLock lock held, since there may be multiple backends trying
* to access the buffer.
*/
int
SIBackendInit(SISeg *segP)
{
int index;
ProcState *stateP = NULL;
/* Look for a free entry in the procState array */
for (index = 0; index < segP->lastBackend; index++)
{
if (segP->procState[index].nextMsgNum < 0) /* inactive slot? */
{
stateP = &segP->procState[index];
break;
}
}
if (stateP == NULL)
{
if (segP->lastBackend < segP->maxBackends)
{
stateP = &segP->procState[segP->lastBackend];
Assert(stateP->nextMsgNum < 0);
segP->lastBackend++;
}
else
{
/* out of procState slots */
MyBackendId = InvalidBackendId;
return 0;
}
}
MyBackendId = (stateP - &segP->procState[0]) + 1;
#ifdef INVALIDDEBUG
elog(DEBUG2, "my backend id is %d", MyBackendId);
#endif /* INVALIDDEBUG */
/* Advertise assigned backend ID in MyProc */
MyProc->backendId = MyBackendId;
/* Reduce free slot count */
segP->freeBackends--;
/* Fetch next local transaction ID into local memory */
nextLocalTransactionId = segP->nextLXID[MyBackendId - 1];
/* mark myself active, with all extant messages already read */
stateP->nextMsgNum = segP->maxMsgNum;
stateP->resetState = false;
/* register exit routine to mark my entry inactive at exit */
on_shmem_exit(CleanupInvalidationState, PointerGetDatum(segP));
return 1;
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* In the Win32 implementation, we acquire semaphores on-demand; the
* maxSemas parameter is just used to size the array that keeps track of
* acquired semas for subsequent releasing. We use anonymous semaphores
* so the semaphores are automatically freed when the last referencing
* process exits.
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
mySemSet = (HANDLE *) malloc(maxSemas * sizeof(HANDLE));
if (mySemSet == NULL)
elog(PANIC, "out of memory");
numSems = 0;
maxSems = maxSemas;
on_shmem_exit(ReleaseSemaphores, 0);
}
/* Initialize a per-walsender data structure for this walsender process */
static void
InitWalSnd(void)
{
int i;
/*
* WalSndCtl should be set up already (we inherit this by fork() or
* EXEC_BACKEND mechanism from the postmaster).
*/
Assert(WalSndCtl != NULL);
Assert(MyWalSnd == NULL);
/*
* Find a free walsender slot and reserve it. If this fails, we must be
* out of WalSnd structures.
*/
for (i = 0; i < max_wal_senders; i++)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];
SpinLockAcquire(&walsnd->mutex);
if (walsnd->pid != 0)
{
SpinLockRelease(&walsnd->mutex);
continue;
}
else
{
/*
* Found a free slot. Reserve it for us.
*/
walsnd->pid = MyProcPid;
MemSet(&walsnd->sentPtr, 0, sizeof(XLogRecPtr));
walsnd->state = WALSNDSTATE_STARTUP;
SpinLockRelease(&walsnd->mutex);
/* don't need the lock anymore */
OwnLatch((Latch *) &walsnd->latch);
MyWalSnd = (WalSnd *) walsnd;
break;
}
}
if (MyWalSnd == NULL)
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("number of requested standby connections "
"exceeds max_wal_senders (currently %d)",
max_wal_senders)));
/* Arrange to clean up at walsender exit */
on_shmem_exit(WalSndKill, 0);
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for Posix, we use
* it to generate the starting semaphore name). In a standalone backend,
* zero will be passed.
*
* In the Posix implementation, we acquire semaphores on-demand; the
* maxSemas parameter is just used to size the array that keeps track of
* acquired semas for subsequent releasing.
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
mySemPointers = (sem_t **) malloc(maxSemas * sizeof(sem_t *));
if (mySemPointers == NULL)
elog(PANIC, "out of memory");
numSems = 0;
maxSems = maxSemas;
nextSemKey = port * 1000;
on_shmem_exit(ReleaseSemaphores, 0);
}
static void
init_lwlock_stats(void)
{
int *LWLockCounter = (int *) ((char *) LWLockArray - 2 * sizeof(int));
int numLocks = LWLockCounter[1];
sh_acquire_counts = calloc(numLocks, sizeof(int));
ex_acquire_counts = calloc(numLocks, sizeof(int));
spin_delay_counts = calloc(numLocks, sizeof(int));
block_counts = calloc(numLocks, sizeof(int));
counts_for_pid = MyProcPid;
on_shmem_exit(print_lwlock_stats, 0);
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for SysV, we use
* it to generate the starting semaphore key). In a standalone backend,
* zero will be passed.
*
* In the SysV implementation, we acquire semaphore sets on-demand; the
* maxSemas parameter is just used to size the array that keeps track of
* acquired sets for subsequent releasing.
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
maxSemaSets = (maxSemas + SEMAS_PER_SET - 1) / SEMAS_PER_SET;
mySemaSets = (IpcSemaphoreId *)
malloc(maxSemaSets * sizeof(IpcSemaphoreId));
if (mySemaSets == NULL)
elog(PANIC, "out of memory");
numSemaSets = 0;
nextSemaKey = port * 1000;
nextSemaNumber = SEMAS_PER_SET; /* force sema set alloc on 1st call */
on_shmem_exit(ReleaseSemaphores, 0);
}
/*
* Establish an AuxProcessResourceOwner for the current process.
*/
void
CreateAuxProcessResourceOwner(void)
{
Assert(AuxProcessResourceOwner == NULL);
Assert(CurrentResourceOwner == NULL);
AuxProcessResourceOwner = ResourceOwnerCreate(NULL, "AuxiliaryProcess");
CurrentResourceOwner = AuxProcessResourceOwner;
/*
* Register a shmem-exit callback for cleanup of aux-process resource
* owner. (This needs to run after, e.g., ShutdownXLOG.)
*/
on_shmem_exit(ReleaseAuxProcessResourcesCallback, 0);
}
/*
* InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
*
* This is separate from InitProcess because we can't acquire LWLocks until
* we've created a PGPROC, but in the EXEC_BACKEND case ProcArrayAdd won't
* work until after we've done CreateSharedMemoryAndSemaphores.
*/
void
InitProcessPhase2(void)
{
Assert(MyProc != NULL);
/*
* Add our PGPROC to the PGPROC array in shared memory.
*/
ProcArrayAdd(MyProc);
/*
* Arrange to clean that up at backend exit.
*/
on_shmem_exit(RemoveProcFromArray, 0);
}
/*
* shmem_startup_hook
*/
static void
pgcl_shmem_startup(void)
{
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
/*
* If we're in the postmaster (or a standalone backend...),
* set up a shmem exit hook to call command_at_shutdown.
*/
if (!IsUnderPostmaster)
on_shmem_exit(pgcl_shmem_shutdown, (Datum) 0);
if (command_at_startup)
ExecuteCommand(command_at_startup, "command_at_startup");
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for SysV, we use
* it to generate the starting semaphore key). In a standalone backend,
* zero will be passed.
*
* In the SysV implementation, we acquire semaphore sets on-demand; the
* maxSemas parameter is just used to size the array that keeps track of
* acquired sets for subsequent releasing.
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
maxSemaSets = (maxSemas + SEMAS_PER_SET - 1) / SEMAS_PER_SET;
mySemaSets = (IpcSemaphoreId *)
malloc(maxSemaSets * sizeof(IpcSemaphoreId));
if (mySemaSets == NULL)
elog(PANIC, "out of memory");
numSemaSets = 0;
nextSemaKey = port * 1000;
nextSemaNumber = SEMAS_PER_SET; /* force sema set alloc on 1st call */
elog((Debug_print_semaphore_detail ? LOG : DEBUG5),
"maxSemaSets %d, nextSemaKey %d, nextSemaNumber %d",
maxSemaSets, nextSemaKey, nextSemaNumber);
on_shmem_exit(ReleaseSemaphores, 0);
}
void PersistentDatabase_DirIterateInit(void)
{
READ_PERSISTENT_STATE_ORDERED_LOCK_DECLARE;
Assert(persistentDatabaseSharedData != NULL);
PersistentDatabase_VerifyInitScan();
PersistentDatabase_ReleaseDirIterator();
READ_PERSISTENT_STATE_ORDERED_LOCK;
if (!iterateOnShmemExitArmed)
{
on_shmem_exit(AtProcExit_PersistentDatabase, 0);
iterateOnShmemExitArmed = true;
}
dirIterateDatabaseDirEntry = NULL;
READ_PERSISTENT_STATE_ORDERED_UNLOCK;
}
static void
init_lwlock_stats(void)
{
HASHCTL ctl;
static MemoryContext lwlock_stats_cxt = NULL;
static bool exit_registered = false;
if (lwlock_stats_cxt != NULL)
MemoryContextDelete(lwlock_stats_cxt);
/*
* The LWLock stats will be updated within a critical section, which
* requires allocating new hash entries. Allocations within a critical
* section are normally not allowed because running out of memory would
* lead to a PANIC, but LWLOCK_STATS is debugging code that's not normally
* turned on in production, so that's an acceptable risk. The hash entries
* are small, so the risk of running out of memory is minimal in practice.
*/
lwlock_stats_cxt = AllocSetContextCreate(TopMemoryContext,
"LWLock stats",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
MemoryContextAllowInCriticalSection(lwlock_stats_cxt, true);
MemSet(&ctl, 0, sizeof(ctl));
ctl.keysize = sizeof(lwlock_stats_key);
ctl.entrysize = sizeof(lwlock_stats);
ctl.hash = tag_hash;
ctl.hcxt = lwlock_stats_cxt;
lwlock_stats_htab = hash_create("lwlock stats", 16384, &ctl,
HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT);
if (!exit_registered)
{
on_shmem_exit(print_lwlock_stats, 0);
exit_registered = true;
}
}
/*
* InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
*
* This is separate from InitProcess because we can't acquire LWLocks until
* we've created a PGPROC, but in the EXEC_BACKEND case there is a good deal
* of stuff to be done before this step that will require LWLock access.
*/
void
InitProcessPhase2(void)
{
Assert(MyProc != NULL);
/*
* We should now know what database we're in, so advertise that. (We need
* not do any locking here, since no other backend can yet see our
* PGPROC.)
*/
Assert(OidIsValid(MyDatabaseId));
MyProc->databaseId = MyDatabaseId;
/*
* Add our PGPROC to the PGPROC array in shared memory.
*/
ProcArrayAdd(MyProc);
/*
* Arrange to clean that up at backend exit.
*/
on_shmem_exit(RemoveProcFromArray, 0);
}
/**
* Initialize global sate of backoff scheduler. This is called during creation
* of shared memory and semaphores.
*/
void
BackoffStateInit()
{
bool found = false;
/* Create or attach to the shared array */
backoffSingleton = (BackoffState *) ShmemInitStruct("Backoff Global State", sizeof(BackoffState), &found);
if (!found)
{
bool ret = false;
/*
* We're the first - initialize.
*/
MemSet(backoffSingleton, 0, sizeof(BackoffState));
backoffSingleton->numEntries = MaxBackends;
backoffSingleton->backendEntries = (BackoffBackendSharedEntry *) ShmemInitStruct("Backoff Backend Entries", mul_size(sizeof(BackoffBackendSharedEntry), backoffSingleton->numEntries), &ret);
backoffSingleton->sweeperInProgress = false;
Assert(!ret);
}
on_shmem_exit(BackoffStateAtExit, 0);
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for Posix, we use
* it to generate the starting semaphore name). In a standalone backend,
* zero will be passed.
*
* In the Posix implementation, we acquire semaphores on-demand; the
* maxSemas parameter is just used to size the arrays. For unnamed
* semaphores, there is an array of PGSemaphoreData structs in shared memory.
* For named semaphores, we keep a postmaster-local array of sem_t pointers,
* which we use for releasing the semphores when done.
* (This design minimizes the dependency of postmaster shutdown on the
* contents of shared memory, which a failed backend might have clobbered.
* We can't do much about the possibility of sem_destroy() crashing, but
* we don't have to expose the counters to other processes.)
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
#ifdef USE_NAMED_POSIX_SEMAPHORES
mySemPointers = (sem_t **) malloc(maxSemas * sizeof(sem_t *));
if (mySemPointers == NULL)
elog(PANIC, "out of memory");
#else
/*
* We must use ShmemAllocUnlocked(), since the spinlock protecting
* ShmemAlloc() won't be ready yet. (This ordering is necessary when we
* are emulating spinlocks with semaphores.)
*/
sharedSemas = (PGSemaphore)
ShmemAllocUnlocked(PGSemaphoreShmemSize(maxSemas));
#endif
numSems = 0;
maxSems = maxSemas;
nextSemKey = port * 1000;
on_shmem_exit(ReleaseSemaphores, 0);
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for SysV, we use
* it to generate the starting semaphore key). In a standalone backend,
* zero will be passed.
*
* In the SysV implementation, we acquire semaphore sets on-demand; the
* maxSemas parameter is just used to size the arrays. There is an array
* of PGSemaphoreData structs in shared memory, and a postmaster-local array
* with one entry per SysV semaphore set, which we use for releasing the
* semaphore sets when done. (This design ensures that postmaster shutdown
* doesn't rely on the contents of shared memory, which a failed backend might
* have clobbered.)
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
/*
* We must use ShmemAllocUnlocked(), since the spinlock protecting
* ShmemAlloc() won't be ready yet. (This ordering is necessary when we
* are emulating spinlocks with semaphores.)
*/
sharedSemas = (PGSemaphore)
ShmemAllocUnlocked(PGSemaphoreShmemSize(maxSemas));
numSharedSemas = 0;
maxSharedSemas = maxSemas;
maxSemaSets = (maxSemas + SEMAS_PER_SET - 1) / SEMAS_PER_SET;
mySemaSets = (IpcSemaphoreId *)
malloc(maxSemaSets * sizeof(IpcSemaphoreId));
if (mySemaSets == NULL)
elog(PANIC, "out of memory");
numSemaSets = 0;
nextSemaKey = port * 1000;
nextSemaNumber = SEMAS_PER_SET; /* force sema set alloc on 1st call */
on_shmem_exit(ReleaseSemaphores, 0);
}
/*
* SharedInvalBackendInit
* Initialize a new backend to operate on the sinval buffer
*/
void
SharedInvalBackendInit(bool sendOnly)
{
int index;
ProcState *stateP = NULL;
SISeg *segP = shmInvalBuffer;
/*
* This can run in parallel with read operations, and for that matter with
* write operations; but not in parallel with additions and removals of
* backends, nor in parallel with SICleanupQueue. It doesn't seem worth
* having a third lock, so we choose to use SInvalWriteLock to serialize
* additions/removals.
*/
LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
/* Look for a free entry in the procState array */
for (index = 0; index < segP->lastBackend; index++)
{
if (segP->procState[index].procPid == 0) /* inactive slot? */
{
stateP = &segP->procState[index];
break;
}
}
if (stateP == NULL)
{
if (segP->lastBackend < segP->maxBackends)
{
stateP = &segP->procState[segP->lastBackend];
Assert(stateP->procPid == 0);
segP->lastBackend++;
}
else
{
/*
* out of procState slots: MaxBackends exceeded -- report normally
*/
MyBackendId = InvalidBackendId;
LWLockRelease(SInvalWriteLock);
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("sorry, too many clients already")));
}
}
MyBackendId = (stateP - &segP->procState[0]) + 1;
/* Advertise assigned backend ID in MyProc */
MyProc->backendId = MyBackendId;
/* Fetch next local transaction ID into local memory */
nextLocalTransactionId = stateP->nextLXID;
/* mark myself active, with all extant messages already read */
stateP->procPid = MyProcPid;
stateP->nextMsgNum = segP->maxMsgNum;
stateP->resetState = false;
stateP->signaled = false;
stateP->sendOnly = sendOnly;
LWLockRelease(SInvalWriteLock);
/* register exit routine to mark my entry inactive at exit */
on_shmem_exit(CleanupInvalidationState, PointerGetDatum(segP));
elog(DEBUG4, "my backend id is %d", MyBackendId);
}
/* --------------------------------
* InitPostgres
* Initialize POSTGRES.
*
* The database can be specified by name, using the in_dbname parameter, or by
* OID, using the dboid parameter. In the latter case, the actual database
* name can be returned to the caller in out_dbname. If out_dbname isn't
* NULL, it must point to a buffer of size NAMEDATALEN.
*
* In bootstrap mode no parameters are used. The autovacuum launcher process
* doesn't use any parameters either, because it only goes far enough to be
* able to read pg_database; it doesn't connect to any particular database.
* In walsender mode only username is used.
*
* As of PostgreSQL 8.2, we expect InitProcess() was already called, so we
* already have a PGPROC struct ... but it's not completely filled in yet.
*
* Note:
* Be very careful with the order of calls in the InitPostgres function.
* --------------------------------
*/
void
InitPostgres(const char *in_dbname, Oid dboid, const char *username,
char *out_dbname)
{
bool bootstrap = IsBootstrapProcessingMode();
bool am_superuser;
char *fullpath;
char dbname[NAMEDATALEN];
elog(DEBUG3, "InitPostgres");
/*
* Add my PGPROC struct to the ProcArray.
*
* Once I have done this, I am visible to other backends!
*/
InitProcessPhase2();
/*
* Initialize my entry in the shared-invalidation manager's array of
* per-backend data.
*
* Sets up MyBackendId, a unique backend identifier.
*/
MyBackendId = InvalidBackendId;
SharedInvalBackendInit(false);
if (MyBackendId > MaxBackends || MyBackendId <= 0)
elog(FATAL, "bad backend ID: %d", MyBackendId);
/* Now that we have a BackendId, we can participate in ProcSignal */
ProcSignalInit(MyBackendId);
/*
* Also set up timeout handlers needed for backend operation. We need
* these in every case except bootstrap.
*/
if (!bootstrap)
{
RegisterTimeout(DEADLOCK_TIMEOUT, CheckDeadLock);
RegisterTimeout(STATEMENT_TIMEOUT, StatementTimeoutHandler);
RegisterTimeout(LOCK_TIMEOUT, LockTimeoutHandler);
}
/*
* bufmgr needs another initialization call too
*/
InitBufferPoolBackend();
/*
* Initialize local process's access to XLOG.
*/
if (IsUnderPostmaster)
{
/*
* The postmaster already started the XLOG machinery, but we need to
* call InitXLOGAccess(), if the system isn't in hot-standby mode.
* This is handled by calling RecoveryInProgress and ignoring the
* result.
*/
(void) RecoveryInProgress();
}
else
{
/*
* We are either a bootstrap process or a standalone backend. Either
* way, start up the XLOG machinery, and register to have it closed
* down at exit.
*/
StartupXLOG();
on_shmem_exit(ShutdownXLOG, 0);
}
/*
* Initialize the relation cache and the system catalog caches. Note that
* no catalog access happens here; we only set up the hashtable structure.
* We must do this before starting a transaction because transaction abort
* would try to touch these hashtables.
*/
RelationCacheInitialize();
InitCatalogCache();
InitPlanCache();
/* Initialize portal manager */
EnablePortalManager();
/* Initialize stats collection --- must happen before first xact */
if (!bootstrap)
pgstat_initialize();
/*
* Load relcache entries for the shared system catalogs. This must create
* at least entries for pg_database and catalogs used for authentication.
*/
RelationCacheInitializePhase2();
/*
* Set up process-exit callback to do pre-shutdown cleanup. This is the
* first before_shmem_exit callback we register; thus, this will be the
* last thing we do before low-level modules like the buffer manager begin
* to close down. We need to have this in place before we begin our first
* transaction --- if we fail during the initialization transaction, as is
* entirely possible, we need the AbortTransaction call to clean up.
*/
before_shmem_exit(ShutdownPostgres, 0);
/* The autovacuum launcher is done here */
if (IsAutoVacuumLauncherProcess())
return;
/*
* Start a new transaction here before first access to db, and get a
* snapshot. We don't have a use for the snapshot itself, but we're
* interested in the secondary effect that it sets RecentGlobalXmin. (This
* is critical for anything that reads heap pages, because HOT may decide
* to prune them even if the process doesn't attempt to modify any
* tuples.)
*/
if (!bootstrap)
{
/* statement_timestamp must be set for timeouts to work correctly */
SetCurrentStatementStartTimestamp();
StartTransactionCommand();
/*
* transaction_isolation will have been set to the default by the
* above. If the default is "serializable", and we are in hot
* standby, we will fail if we don't change it to something lower.
* Fortunately, "read committed" is plenty good enough.
*/
XactIsoLevel = XACT_READ_COMMITTED;
(void) GetTransactionSnapshot();
}
/*
* Perform client authentication if necessary, then figure out our
* postgres user ID, and see if we are a superuser.
*
* In standalone mode and in autovacuum worker processes, we use a fixed
* ID, otherwise we figure it out from the authenticated user name.
*/
if (bootstrap || IsAutoVacuumWorkerProcess())
{
InitializeSessionUserIdStandalone();
am_superuser = true;
}
else if (!IsUnderPostmaster)
{
InitializeSessionUserIdStandalone();
am_superuser = true;
if (!ThereIsAtLeastOneRole())
ereport(WARNING,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("no roles are defined in this database system"),
errhint("You should immediately run CREATE USER \"%s\" SUPERUSER;.",
username)));
}
else if (IsBackgroundWorker)
{
if (username == NULL)
{
InitializeSessionUserIdStandalone();
am_superuser = true;
}
else
{
InitializeSessionUserId(username);
am_superuser = superuser();
}
}
else
{
/* normal multiuser case */
Assert(MyProcPort != NULL);
PerformAuthentication(MyProcPort);
InitializeSessionUserId(username);
am_superuser = superuser();
}
/*
* If we're trying to shut down, only superusers can connect, and new
* replication connections are not allowed.
*/
if ((!am_superuser || am_walsender) &&
MyProcPort != NULL &&
MyProcPort->canAcceptConnections == CAC_WAITBACKUP)
{
if (am_walsender)
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("new replication connections are not allowed during database shutdown")));
else
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to connect during database shutdown")));
}
/*
* Binary upgrades only allowed super-user connections
*/
if (IsBinaryUpgrade && !am_superuser)
{
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to connect in binary upgrade mode")));
}
/*
* The last few connections slots are reserved for superusers. Although
* replication connections currently require superuser privileges, we
* don't allow them to consume the reserved slots, which are intended for
* interactive use.
*/
if ((!am_superuser || am_walsender) &&
ReservedBackends > 0 &&
!HaveNFreeProcs(ReservedBackends))
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("remaining connection slots are reserved for non-replication superuser connections")));
/* Check replication permissions needed for walsender processes. */
if (am_walsender)
{
Assert(!bootstrap);
if (!superuser() && !has_rolreplication(GetUserId()))
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser or replication role to start walsender")));
}
/*
* If this is a plain walsender only supporting physical replication, we
* don't want to connect to any particular database. Just finish the
* backend startup by processing any options from the startup packet, and
* we're done.
*/
if (am_walsender && !am_db_walsender)
{
/* process any options passed in the startup packet */
if (MyProcPort != NULL)
process_startup_options(MyProcPort, am_superuser);
/* Apply PostAuthDelay as soon as we've read all options */
if (PostAuthDelay > 0)
pg_usleep(PostAuthDelay * 1000000L);
/* initialize client encoding */
InitializeClientEncoding();
/* report this backend in the PgBackendStatus array */
pgstat_bestart();
/* close the transaction we started above */
CommitTransactionCommand();
return;
}
/*
* Set up the global variables holding database id and default tablespace.
* But note we won't actually try to touch the database just yet.
*
* We take a shortcut in the bootstrap case, otherwise we have to look up
* the db's entry in pg_database.
*/
if (bootstrap)
{
MyDatabaseId = TemplateDbOid;
MyDatabaseTableSpace = DEFAULTTABLESPACE_OID;
}
else if (in_dbname != NULL)
{
HeapTuple tuple;
Form_pg_database dbform;
tuple = GetDatabaseTuple(in_dbname);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", in_dbname)));
dbform = (Form_pg_database) GETSTRUCT(tuple);
MyDatabaseId = HeapTupleGetOid(tuple);
MyDatabaseTableSpace = dbform->dattablespace;
/* take database name from the caller, just for paranoia */
strlcpy(dbname, in_dbname, sizeof(dbname));
}
else if (OidIsValid(dboid))
{
/* caller specified database by OID */
HeapTuple tuple;
Form_pg_database dbform;
tuple = GetDatabaseTupleByOid(dboid);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database %u does not exist", dboid)));
dbform = (Form_pg_database) GETSTRUCT(tuple);
MyDatabaseId = HeapTupleGetOid(tuple);
MyDatabaseTableSpace = dbform->dattablespace;
Assert(MyDatabaseId == dboid);
strlcpy(dbname, NameStr(dbform->datname), sizeof(dbname));
/* pass the database name back to the caller */
if (out_dbname)
strcpy(out_dbname, dbname);
}
else
{
/*
* If this is a background worker not bound to any particular
* database, we're done now. Everything that follows only makes
* sense if we are bound to a specific database. We do need to
* close the transaction we started before returning.
*/
if (!bootstrap)
CommitTransactionCommand();
return;
}
/*
* Now, take a writer's lock on the database we are trying to connect to.
* If there is a concurrently running DROP DATABASE on that database, this
* will block us until it finishes (and has committed its update of
* pg_database).
*
* Note that the lock is not held long, only until the end of this startup
* transaction. This is OK since we will advertise our use of the
* database in the ProcArray before dropping the lock (in fact, that's the
* next thing to do). Anyone trying a DROP DATABASE after this point will
* see us in the array once they have the lock. Ordering is important for
* this because we don't want to advertise ourselves as being in this
* database until we have the lock; otherwise we create what amounts to a
* deadlock with CountOtherDBBackends().
*
* Note: use of RowExclusiveLock here is reasonable because we envision
* our session as being a concurrent writer of the database. If we had a
* way of declaring a session as being guaranteed-read-only, we could use
* AccessShareLock for such sessions and thereby not conflict against
* CREATE DATABASE.
*/
if (!bootstrap)
LockSharedObject(DatabaseRelationId, MyDatabaseId, 0,
RowExclusiveLock);
/*
* Now we can mark our PGPROC entry with the database ID.
*
* We assume this is an atomic store so no lock is needed; though actually
* things would work fine even if it weren't atomic. Anyone searching the
* ProcArray for this database's ID should hold the database lock, so they
* would not be executing concurrently with this store. A process looking
* for another database's ID could in theory see a chance match if it read
* a partially-updated databaseId value; but as long as all such searches
* wait and retry, as in CountOtherDBBackends(), they will certainly see
* the correct value on their next try.
*/
MyProc->databaseId = MyDatabaseId;
/*
* We established a catalog snapshot while reading pg_authid and/or
* pg_database; but until we have set up MyDatabaseId, we won't react to
* incoming sinval messages for unshared catalogs, so we won't realize it
* if the snapshot has been invalidated. Assume it's no good anymore.
*/
InvalidateCatalogSnapshot();
/*
* Recheck pg_database to make sure the target database hasn't gone away.
* If there was a concurrent DROP DATABASE, this ensures we will die
* cleanly without creating a mess.
*/
if (!bootstrap)
{
HeapTuple tuple;
tuple = GetDatabaseTuple(dbname);
if (!HeapTupleIsValid(tuple) ||
MyDatabaseId != HeapTupleGetOid(tuple) ||
MyDatabaseTableSpace != ((Form_pg_database) GETSTRUCT(tuple))->dattablespace)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", dbname),
errdetail("It seems to have just been dropped or renamed.")));
}
/*
* Now we should be able to access the database directory safely. Verify
* it's there and looks reasonable.
*/
fullpath = GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace);
if (!bootstrap)
{
if (access(fullpath, F_OK) == -1)
{
if (errno == ENOENT)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist",
dbname),
errdetail("The database subdirectory \"%s\" is missing.",
fullpath)));
else
ereport(FATAL,
(errcode_for_file_access(),
errmsg("could not access directory \"%s\": %m",
fullpath)));
}
ValidatePgVersion(fullpath);
}
SetDatabasePath(fullpath);
/*
* It's now possible to do real access to the system catalogs.
*
* Load relcache entries for the system catalogs. This must create at
* least the minimum set of "nailed-in" cache entries.
*/
RelationCacheInitializePhase3();
/* set up ACL framework (so CheckMyDatabase can check permissions) */
initialize_acl();
/*
* Re-read the pg_database row for our database, check permissions and set
* up database-specific GUC settings. We can't do this until all the
* database-access infrastructure is up. (Also, it wants to know if the
* user is a superuser, so the above stuff has to happen first.)
*/
if (!bootstrap)
CheckMyDatabase(dbname, am_superuser);
/*
* Now process any command-line switches and any additional GUC variable
* settings passed in the startup packet. We couldn't do this before
* because we didn't know if client is a superuser.
*/
if (MyProcPort != NULL)
process_startup_options(MyProcPort, am_superuser);
/* Process pg_db_role_setting options */
process_settings(MyDatabaseId, GetSessionUserId());
/* Apply PostAuthDelay as soon as we've read all options */
if (PostAuthDelay > 0)
pg_usleep(PostAuthDelay * 1000000L);
/*
* Initialize various default states that can't be set up until we've
* selected the active user and gotten the right GUC settings.
*/
/* set default namespace search path */
InitializeSearchPath();
/* initialize client encoding */
InitializeClientEncoding();
/* report this backend in the PgBackendStatus array */
if (!bootstrap)
pgstat_bestart();
/* close the transaction we started above */
if (!bootstrap)
CommitTransactionCommand();
}
/*
* LWLockAcquire - acquire a lightweight lock in the specified mode
*
* If the lock is not available, sleep until it is.
*
* Side effect: cancel/die interrupts are held off until lock release.
*/
void
LWLockAcquire(LWLockId lockid, LWLockMode mode)
{
volatile LWLock *lock = &(LWLockArray[lockid].lock);
PGPROC *proc = MyProc;
bool retry = false;
int extraWaits = 0;
PRINT_LWDEBUG("LWLockAcquire", lockid, lock);
#ifdef LWLOCK_STATS
/* Set up local count state first time through in a given process */
if (counts_for_pid != MyProcPid)
{
int *LWLockCounter = (int *) ((char *) LWLockArray - 2 * sizeof(int));
int numLocks = LWLockCounter[1];
sh_acquire_counts = calloc(numLocks, sizeof(int));
ex_acquire_counts = calloc(numLocks, sizeof(int));
block_counts = calloc(numLocks, sizeof(int));
counts_for_pid = MyProcPid;
on_shmem_exit(print_lwlock_stats, 0);
}
/* Count lock acquisition attempts */
if (mode == LW_EXCLUSIVE)
ex_acquire_counts[lockid]++;
else
sh_acquire_counts[lockid]++;
#endif /* LWLOCK_STATS */
/*
* We can't wait if we haven't got a PGPROC. This should only occur
* during bootstrap or shared memory initialization. Put an Assert here
* to catch unsafe coding practices.
*/
Assert(!(proc == NULL && IsUnderPostmaster));
/* Ensure we will have room to remember the lock */
if (num_held_lwlocks >= MAX_SIMUL_LWLOCKS)
elog(ERROR, "too many LWLocks taken");
/*
* Lock out cancel/die interrupts until we exit the code section protected
* by the LWLock. This ensures that interrupts will not interfere with
* manipulations of data structures in shared memory.
*/
HOLD_INTERRUPTS();
/*
* Loop here to try to acquire lock after each time we are signaled by
* LWLockRelease.
*
* NOTE: it might seem better to have LWLockRelease actually grant us the
* lock, rather than retrying and possibly having to go back to sleep. But
* in practice that is no good because it means a process swap for every
* lock acquisition when two or more processes are contending for the same
* lock. Since LWLocks are normally used to protect not-very-long
* sections of computation, a process needs to be able to acquire and
* release the same lock many times during a single CPU time slice, even
* in the presence of contention. The efficiency of being able to do that
* outweighs the inefficiency of sometimes wasting a process dispatch
* cycle because the lock is not free when a released waiter finally gets
* to run. See pgsql-hackers archives for 29-Dec-01.
*/
for (;;)
{
bool mustwait;
/* Acquire mutex. Time spent holding mutex should be short! */
SpinLockAcquire(&lock->mutex);
/* If retrying, allow LWLockRelease to release waiters again */
if (retry)
lock->releaseOK = true;
/* If I can get the lock, do so quickly. */
if (mode == LW_EXCLUSIVE)
{
if (lock->exclusive == 0 && lock->shared == 0)
{
lock->exclusive++;
mustwait = false;
}
else
mustwait = true;
}
else
{
if (lock->exclusive == 0)
{
lock->shared++;
mustwait = false;
}
else
mustwait = true;
}
if (!mustwait)
break; /* got the lock */
/*
* Add myself to wait queue.
*
* If we don't have a PGPROC structure, there's no way to wait. This
* should never occur, since MyProc should only be null during shared
* memory initialization.
*/
if (proc == NULL)
elog(PANIC, "cannot wait without a PGPROC structure");
proc->lwWaiting = true;
proc->lwExclusive = (mode == LW_EXCLUSIVE);
proc->lwWaitLink = NULL;
if (lock->head == NULL)
lock->head = proc;
else
lock->tail->lwWaitLink = proc;
lock->tail = proc;
/* Can release the mutex now */
SpinLockRelease(&lock->mutex);
/*
* Wait until awakened.
*
* Since we share the process wait semaphore with the regular lock
* manager and ProcWaitForSignal, and we may need to acquire an LWLock
* while one of those is pending, it is possible that we get awakened
* for a reason other than being signaled by LWLockRelease. If so,
* loop back and wait again. Once we've gotten the LWLock,
* re-increment the sema by the number of additional signals received,
* so that the lock manager or signal manager will see the received
* signal when it next waits.
*/
LOG_LWDEBUG("LWLockAcquire", lockid, "waiting");
#ifdef LWLOCK_STATS
block_counts[lockid]++;
#endif
TRACE_POSTGRESQL_LWLOCK_WAIT_START(lockid, mode);
for (;;)
{
/* "false" means cannot accept cancel/die interrupt here. */
PGSemaphoreLock(&proc->sem, false);
if (!proc->lwWaiting)
break;
extraWaits++;
}
TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(lockid, mode);
LOG_LWDEBUG("LWLockAcquire", lockid, "awakened");
/* Now loop back and try to acquire lock again. */
retry = true;
}
/* We are done updating shared state of the lock itself. */
SpinLockRelease(&lock->mutex);
TRACE_POSTGRESQL_LWLOCK_ACQUIRE(lockid, mode);
/* Add lock to list of locks held by this backend */
held_lwlocks[num_held_lwlocks++] = lockid;
/*
* Fix the process wait semaphore's count for any absorbed wakeups.
*/
while (extraWaits-- > 0)
PGSemaphoreUnlock(&proc->sem);
}
/*
* LWLockAcquire - acquire a lightweight lock in the specified mode
*
* If the lock is not available, sleep until it is.
*
* Side effect: cancel/die interrupts are held off until lock release.
*/
void
LWLockAcquire(LWLockId lockid, LWLockMode mode)
{
volatile LWLock *lock = &(LWLockArray[lockid].lock);
#if LWLOCK_LOCK_PARTS > 1
volatile LWLockPart *part = LWLOCK_PART(lock, lockid, MyBackendId);
#endif
PGPROC *proc = MyProc;
bool retry = false;
int extraWaits = 0;
PRINT_LWDEBUG("LWLockAcquire", lockid, lock);
#ifdef LWLOCK_STATS
/* Set up local count state first time through in a given process */
if (counts_for_pid != MyProcPid)
{
int *LWLockCounter = (int *) ((char *) LWLockArray - 2 * sizeof(int));
int numLocks = LWLockCounter[1];
sh_acquire_counts = calloc(numLocks, sizeof(int));
ex_acquire_counts = calloc(numLocks, sizeof(int));
block_counts = calloc(numLocks, sizeof(int));
counts_for_pid = MyProcPid;
on_shmem_exit(print_lwlock_stats, 0);
}
/* Count lock acquisition attempts */
if (mode == LW_EXCLUSIVE)
ex_acquire_counts[lockid]++;
else
sh_acquire_counts[lockid]++;
#endif /* LWLOCK_STATS */
/*
* We can't wait if we haven't got a PGPROC. This should only occur
* during bootstrap or shared memory initialization. Put an Assert here
* to catch unsafe coding practices.
*/
Assert(!(proc == NULL && IsUnderPostmaster));
/* Ensure we will have room to remember the lock */
if (num_held_lwlocks >= MAX_SIMUL_LWLOCKS)
elog(ERROR, "too many LWLocks taken");
/*
* Lock out cancel/die interrupts until we exit the code section protected
* by the LWLock. This ensures that interrupts will not interfere with
* manipulations of data structures in shared memory.
*/
HOLD_INTERRUPTS();
/*
* Loop here to try to acquire lock after each time we are signaled by
* LWLockRelease.
*
* NOTE: it might seem better to have LWLockRelease actually grant us the
* lock, rather than retrying and possibly having to go back to sleep. But
* in practice that is no good because it means a process swap for every
* lock acquisition when two or more processes are contending for the same
* lock. Since LWLocks are normally used to protect not-very-long
* sections of computation, a process needs to be able to acquire and
* release the same lock many times during a single CPU time slice, even
* in the presence of contention. The efficiency of being able to do that
* outweighs the inefficiency of sometimes wasting a process dispatch
* cycle because the lock is not free when a released waiter finally gets
* to run. See pgsql-hackers archives for 29-Dec-01.
*/
for (;;)
{
bool mustwait;
if (mode == LW_SHARED)
{
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
/* Increment shared counter partition. If there's no contention,
* this is sufficient to take the lock
*/
LWLOCK_PART_SHARED_POSTINC_ATOMIC(lock, lockid, part, MyBackendId);
LWLOCK_PART_SHARED_FENCE();
/* A concurrent exclusive locking attempt does the following
* three steps
* 1) Acquire mutex
* 2) Check shared counter partitions for readers.
* 3a) If found add proc to wait queue, block, restart at (1)
* 3b) If not found, set exclusive flag, continue with (4)
* 4) Enter protected section
* The fence after the atomic add above ensures that no further
* such attempt can proceed to (3b) or beyond. There may be
* pre-existing exclusive locking attempts at step (3b) or beyond,
* but we can recognize those by either the mutex being taken, or
* the exclusive flag being set. Conversely, if we see neither, we
* may proceed and enter the protected section.
*
* FIXME: This doesn't work if slock_t is a struct or doesn't
* use 0 for state "unlocked".
*/
if ((lock->mutex == 0) && (lock->exclusive == 0)) {
/* If retrying, allow LWLockRelease to release waiters again.
* Usually this happens after we acquired the mutex, but if
* we skip that, we still need to set releaseOK.
*
* Acquiring the mutex here is not really an option - if many
* reader are awoken simultaneously by an exclusive unlock,
* that would be a source of considerable contention.
*
* Fotunately, this is safe even without the mutex. First,
* there actually cannot be any non-fast path unlocking
* attempt in progress, because we'd then either still see
* the exclusive flag set or the mutex being taken. And
* even if there was, and such an attempt cleared the flag
* immediately after we set it, it'd also wake up some waiter
* who'd then re-set the flag.
*
* The only reason to do this here, and not directly
* after returning from PGSemaphoreLock(), is that it seems
* benefical to make SpinLockAcquire() the first thing to
* touch the lock if possible, in case we acquire the spin
* lock at all. That way, the cache line doesn't go through
* a possible shared state, but instead directly to exclusive.
* On Opterons at least, there seems to be a difference, c.f.
* the comment above tas() for x86_64 in s_lock.h
*/
if (retry && !lock->releaseOK)
lock->releaseOK = true;
goto lock_acquired;
}
/* At this point, we don't know if the concurrent exclusive locker
* has proceeded to (3b) or blocked. We must take the mutex and
* re-check
*/
#endif /* LWLOCK_PART_SHARED_OPS_ATOMIC */
/* Acquire mutex. Time spent holding mutex should be short! */
SpinLockAcquire(&lock->mutex);
if (lock->exclusive == 0)
{
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
/* Already incremented the shared counter partition above */
#else
lock->shared++;
#endif
mustwait = false;
}
else
{
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
/* Must undo shared counter partition increment. Note that
* we *need* to do that while holding the mutex. Otherwise,
* the exclusive lock could be released and attempted to be
* re-acquired before we undo the increment. That attempt
* would then block, even though there'd be no lock holder
* left
*/
LWLOCK_PART_SHARED_POSTDEC_ATOMIC(lock, lockid, part, MyBackendId);
#endif
mustwait = true;
}
}
else
{
/* Step (1). Acquire mutex. Time spent holding mutex should be
* short!
*/
SpinLockAcquire(&lock->mutex);
if (lock->exclusive == 0)
{
/* Step (2). Check for shared lockers. This surely happens
* after (1), otherwise SpinLockAcquire() is broken. Lock
* acquire semantics demand that no load must be re-ordered
* from after a lock acquisition to before, for obvious
* reasons.
*/
LWLOCK_IS_SHARED(mustwait, lock, lockid);
if (!mustwait) {
/* Step (3a). Set exclusive flag. This surely happens
* after (2) because it depends on the result of (2),
* no matter how much reordering is going on here.
*/
lock->exclusive++;
}
}
else
mustwait = true;
}
/* If retrying, allow LWLockRelease to release waiters again.
* This is also separately done in the LW_SHARED early exit case
* above, and in contrast to there we don't hold the mutex there.
* See the comment there for why this is safe
*/
if (retry)
lock->releaseOK = true;
if (!mustwait)
break; /* got the lock */
/*
* Step (3b). Add myself to wait queue.
*
* If we don't have a PGPROC structure, there's no way to wait. This
* should never occur, since MyProc should only be null during shared
* memory initialization.
*/
if (proc == NULL)
elog(PANIC, "cannot wait without a PGPROC structure");
proc->lwWaiting = true;
proc->lwExclusive = (mode == LW_EXCLUSIVE);
proc->lwWaitLink = NULL;
if (lock->head == NULL)
lock->head = proc;
else
lock->tail->lwWaitLink = proc;
lock->tail = proc;
/* Can release the mutex now */
SpinLockRelease(&lock->mutex);
/*
* Wait until awakened.
*
* Since we share the process wait semaphore with the regular lock
* manager and ProcWaitForSignal, and we may need to acquire an LWLock
* while one of those is pending, it is possible that we get awakened
* for a reason other than being signaled by LWLockRelease. If so,
* loop back and wait again. Once we've gotten the LWLock,
* re-increment the sema by the number of additional signals received,
* so that the lock manager or signal manager will see the received
* signal when it next waits.
*/
LOG_LWDEBUG("LWLockAcquire", lockid, "waiting");
#ifdef LWLOCK_STATS
block_counts[lockid]++;
#endif
TRACE_POSTGRESQL_LWLOCK_WAIT_START(lockid, mode);
for (;;)
{
/* "false" means cannot accept cancel/die interrupt here. */
PGSemaphoreLock(&proc->sem, false);
if (!proc->lwWaiting)
break;
extraWaits++;
}
TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(lockid, mode);
LOG_LWDEBUG("LWLockAcquire", lockid, "awakened");
/* Now loop back and try to acquire lock again. */
retry = true;
}
/* We are done updating shared state of the lock itself. */
SpinLockRelease(&lock->mutex);
/* Step 4. Enter protected section. This surely happens after (3),
* this time because lock release semantics demand that no store
* must be moved from before a lock release to after the release,
* again for obvious reasons
*/
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
lock_acquired:
#endif
TRACE_POSTGRESQL_LWLOCK_ACQUIRE(lockid, mode);
/* Add lock to list of locks held by this backend */
held_lwlocks[num_held_lwlocks] = lockid;
held_lwlocks_mode[num_held_lwlocks] = mode;
++num_held_lwlocks;
/*
* Fix the process wait semaphore's count for any absorbed wakeups.
*/
while (extraWaits-- > 0)
PGSemaphoreUnlock(&proc->sem);
}
/*
* shmem_startup hook: allocate or attach to shared memory,
* then load any pre-existing statistics from file.
*/
static void
pgss_shmem_startup(void)
{
bool found;
HASHCTL info;
FILE *file;
uint32 header;
int32 num;
int32 i;
int query_size;
int buffer_size;
char *buffer = NULL;
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
/* reset in case this is a restart within the postmaster */
pgss = NULL;
pgss_hash = NULL;
/*
* Create or attach to the shared memory state, including hash table
*/
LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
pgss = ShmemInitStruct("pg_stat_statements",
sizeof(pgssSharedState),
&found);
if (!found)
{
/* First time through ... */
pgss->lock = LWLockAssign();
pgss->query_size = pgstat_track_activity_query_size;
}
/* Be sure everyone agrees on the hash table entry size */
query_size = pgss->query_size;
memset(&info, 0, sizeof(info));
info.keysize = sizeof(pgssHashKey);
info.entrysize = offsetof(pgssEntry, query) +query_size;
info.hash = pgss_hash_fn;
info.match = pgss_match_fn;
pgss_hash = ShmemInitHash("pg_stat_statements hash",
pgss_max, pgss_max,
&info,
HASH_ELEM | HASH_FUNCTION | HASH_COMPARE);
LWLockRelease(AddinShmemInitLock);
/*
* If we're in the postmaster (or a standalone backend...), set up a shmem
* exit hook to dump the statistics to disk.
*/
if (!IsUnderPostmaster)
on_shmem_exit(pgss_shmem_shutdown, (Datum) 0);
/*
* Attempt to load old statistics from the dump file, if this is the first
* time through and we weren't told not to.
*/
if (found || !pgss_save)
return;
/*
* Note: we don't bother with locks here, because there should be no other
* processes running when this code is reached.
*/
file = AllocateFile(PGSS_DUMP_FILE, PG_BINARY_R);
if (file == NULL)
{
if (errno == ENOENT)
return; /* ignore not-found error */
goto error;
}
buffer_size = query_size;
buffer = (char *) palloc(buffer_size);
if (fread(&header, sizeof(uint32), 1, file) != 1 ||
header != PGSS_FILE_HEADER ||
fread(&num, sizeof(int32), 1, file) != 1)
goto error;
for (i = 0; i < num; i++)
{
pgssEntry temp;
pgssEntry *entry;
if (fread(&temp, offsetof(pgssEntry, mutex), 1, file) != 1)
goto error;
/* Encoding is the only field we can easily sanity-check */
if (!PG_VALID_BE_ENCODING(temp.key.encoding))
goto error;
/* Previous incarnation might have had a larger query_size */
if (temp.key.query_len >= buffer_size)
{
buffer = (char *) repalloc(buffer, temp.key.query_len + 1);
buffer_size = temp.key.query_len + 1;
}
if (fread(buffer, 1, temp.key.query_len, file) != temp.key.query_len)
goto error;
buffer[temp.key.query_len] = '\0';
/* Clip to available length if needed */
if (temp.key.query_len >= query_size)
temp.key.query_len = pg_encoding_mbcliplen(temp.key.encoding,
buffer,
temp.key.query_len,
query_size - 1);
temp.key.query_ptr = buffer;
/* make the hashtable entry (discards old entries if too many) */
entry = entry_alloc(&temp.key);
/* copy in the actual stats */
entry->counters = temp.counters;
}
pfree(buffer);
FreeFile(file);
return;
error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read pg_stat_statement file \"%s\": %m",
PGSS_DUMP_FILE)));
if (buffer)
pfree(buffer);
if (file)
FreeFile(file);
/* If possible, throw away the bogus file; ignore any error */
unlink(PGSS_DUMP_FILE);
}
/* --------------------------------
* InitPostgres
* Initialize POSTGRES.
*
* The database can be specified by name, using the in_dbname parameter, or by
* OID, using the dboid parameter. In the latter case, the actual database
* name can be returned to the caller in out_dbname. If out_dbname isn't
* NULL, it must point to a buffer of size NAMEDATALEN.
*
* In bootstrap mode no parameters are used. The autovacuum launcher process
* doesn't use any parameters either, because it only goes far enough to be
* able to read pg_database; it doesn't connect to any particular database.
* In walsender mode only username is used.
*
* As of PostgreSQL 8.2, we expect InitProcess() was already called, so we
* already have a PGPROC struct ... but it's not completely filled in yet.
*
* Note:
* Be very careful with the order of calls in the InitPostgres function.
* --------------------------------
*/
void
InitPostgres(const char *in_dbname, Oid dboid, const char *username,
char *out_dbname)
{
bool bootstrap = IsBootstrapProcessingMode();
bool am_superuser;
GucContext gucctx;
char *fullpath;
char dbname[NAMEDATALEN];
elog(DEBUG3, "InitPostgres");
/*
* Add my PGPROC struct to the ProcArray.
*
* Once I have done this, I am visible to other backends!
*/
InitProcessPhase2();
/*
* Initialize my entry in the shared-invalidation manager's array of
* per-backend data.
*
* Sets up MyBackendId, a unique backend identifier.
*/
MyBackendId = InvalidBackendId;
SharedInvalBackendInit(false);
if (MyBackendId > MaxBackends || MyBackendId <= 0)
elog(FATAL, "bad backend id: %d", MyBackendId);
/* Now that we have a BackendId, we can participate in ProcSignal */
ProcSignalInit(MyBackendId);
/*
* bufmgr needs another initialization call too
*/
InitBufferPoolBackend();
/*
* Initialize local process's access to XLOG, if appropriate. In
* bootstrap case we skip this since StartupXLOG() was run instead.
*/
if (!bootstrap)
(void) RecoveryInProgress();
/*
* Initialize the relation cache and the system catalog caches. Note that
* no catalog access happens here; we only set up the hashtable structure.
* We must do this before starting a transaction because transaction abort
* would try to touch these hashtables.
*/
RelationCacheInitialize();
InitCatalogCache();
InitPlanCache();
/* Initialize portal manager */
EnablePortalManager();
/* Initialize stats collection --- must happen before first xact */
if (!bootstrap)
pgstat_initialize();
/*
* Load relcache entries for the shared system catalogs. This must create
* at least an entry for pg_database.
*/
RelationCacheInitializePhase2();
/*
* Set up process-exit callback to do pre-shutdown cleanup. This has to
* be after we've initialized all the low-level modules like the buffer
* manager, because during shutdown this has to run before the low-level
* modules start to close down. On the other hand, we want it in place
* before we begin our first transaction --- if we fail during the
* initialization transaction, as is entirely possible, we need the
* AbortTransaction call to clean up.
*/
on_shmem_exit(ShutdownPostgres, 0);
/* The autovacuum launcher is done here */
if (IsAutoVacuumLauncherProcess())
return;
/*
* Start a new transaction here before first access to db, and get a
* snapshot. We don't have a use for the snapshot itself, but we're
* interested in the secondary effect that it sets RecentGlobalXmin. (This
* is critical for anything that reads heap pages, because HOT may decide
* to prune them even if the process doesn't attempt to modify any
* tuples.)
*/
if (!bootstrap)
{
StartTransactionCommand();
(void) GetTransactionSnapshot();
}
/*
* Set up the global variables holding database id and default tablespace.
* But note we won't actually try to touch the database just yet.
*
* We take a shortcut in the bootstrap and walsender case, otherwise we
* have to look up the db's entry in pg_database.
*/
if (bootstrap || am_walsender)
{
MyDatabaseId = TemplateDbOid;
MyDatabaseTableSpace = DEFAULTTABLESPACE_OID;
}
else if (in_dbname != NULL)
{
HeapTuple tuple;
Form_pg_database dbform;
tuple = GetDatabaseTuple(in_dbname);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", in_dbname)));
dbform = (Form_pg_database) GETSTRUCT(tuple);
MyDatabaseId = HeapTupleGetOid(tuple);
MyDatabaseTableSpace = dbform->dattablespace;
/* take database name from the caller, just for paranoia */
strlcpy(dbname, in_dbname, sizeof(dbname));
}
else
{
/* caller specified database by OID */
HeapTuple tuple;
Form_pg_database dbform;
tuple = GetDatabaseTupleByOid(dboid);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database %u does not exist", dboid)));
dbform = (Form_pg_database) GETSTRUCT(tuple);
MyDatabaseId = HeapTupleGetOid(tuple);
MyDatabaseTableSpace = dbform->dattablespace;
Assert(MyDatabaseId == dboid);
strlcpy(dbname, NameStr(dbform->datname), sizeof(dbname));
/* pass the database name back to the caller */
if (out_dbname)
strcpy(out_dbname, dbname);
}
/* Now we can mark our PGPROC entry with the database ID */
/* (We assume this is an atomic store so no lock is needed) */
MyProc->databaseId = MyDatabaseId;
/*
* Now, take a writer's lock on the database we are trying to connect to.
* If there is a concurrently running DROP DATABASE on that database, this
* will block us until it finishes (and has committed its update of
* pg_database).
*
* Note that the lock is not held long, only until the end of this startup
* transaction. This is OK since we are already advertising our use of
* the database in the PGPROC array; anyone trying a DROP DATABASE after
* this point will see us there.
*
* Note: use of RowExclusiveLock here is reasonable because we envision
* our session as being a concurrent writer of the database. If we had a
* way of declaring a session as being guaranteed-read-only, we could use
* AccessShareLock for such sessions and thereby not conflict against
* CREATE DATABASE.
*/
if (!bootstrap && !am_walsender)
LockSharedObject(DatabaseRelationId, MyDatabaseId, 0,
RowExclusiveLock);
/*
* Recheck pg_database to make sure the target database hasn't gone away.
* If there was a concurrent DROP DATABASE, this ensures we will die
* cleanly without creating a mess.
*/
if (!bootstrap && !am_walsender)
{
HeapTuple tuple;
tuple = GetDatabaseTuple(dbname);
if (!HeapTupleIsValid(tuple) ||
MyDatabaseId != HeapTupleGetOid(tuple) ||
MyDatabaseTableSpace != ((Form_pg_database) GETSTRUCT(tuple))->dattablespace)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", dbname),
errdetail("It seems to have just been dropped or renamed.")));
}
/*
* Now we should be able to access the database directory safely. Verify
* it's there and looks reasonable.
*/
fullpath = GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace);
if (!bootstrap && !am_walsender)
{
if (access(fullpath, F_OK) == -1)
{
if (errno == ENOENT)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist",
dbname),
errdetail("The database subdirectory \"%s\" is missing.",
fullpath)));
else
ereport(FATAL,
(errcode_for_file_access(),
errmsg("could not access directory \"%s\": %m",
fullpath)));
}
ValidatePgVersion(fullpath);
}
SetDatabasePath(fullpath);
/*
* It's now possible to do real access to the system catalogs.
*
* Load relcache entries for the system catalogs. This must create at
* least the minimum set of "nailed-in" cache entries.
*/
RelationCacheInitializePhase3();
/*
* Perform client authentication if necessary, then figure out our
* postgres user ID, and see if we are a superuser.
*
* In standalone mode and in autovacuum worker processes, we use a fixed
* ID, otherwise we figure it out from the authenticated user name.
*/
if (bootstrap || IsAutoVacuumWorkerProcess())
{
InitializeSessionUserIdStandalone();
am_superuser = true;
}
else if (!IsUnderPostmaster)
{
InitializeSessionUserIdStandalone();
am_superuser = true;
if (!ThereIsAtLeastOneRole())
ereport(WARNING,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("no roles are defined in this database system"),
errhint("You should immediately run CREATE USER \"%s\" SUPERUSER;.",
username)));
}
else
{
/* normal multiuser case */
Assert(MyProcPort != NULL);
PerformAuthentication(MyProcPort);
InitializeSessionUserId(username);
am_superuser = superuser();
}
/* set up ACL framework (so CheckMyDatabase can check permissions) */
initialize_acl();
/* Process pg_db_role_setting options */
process_settings(MyDatabaseId, GetSessionUserId());
/*
* Re-read the pg_database row for our database, check permissions and set
* up database-specific GUC settings. We can't do this until all the
* database-access infrastructure is up. (Also, it wants to know if the
* user is a superuser, so the above stuff has to happen first.)
*/
if (!bootstrap && !am_walsender)
CheckMyDatabase(dbname, am_superuser);
/*
* If we're trying to shut down, only superusers can connect.
*/
if (!am_superuser &&
MyProcPort != NULL &&
MyProcPort->canAcceptConnections == CAC_WAITBACKUP)
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to connect during database shutdown")));
/*
* Check a normal user hasn't connected to a superuser reserved slot.
*/
if (!am_superuser &&
ReservedBackends > 0 &&
!HaveNFreeProcs(ReservedBackends))
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("connection limit exceeded for non-superusers")));
/*
* Now process any command-line switches that were included in the startup
* packet, if we are in a regular backend. We couldn't do this before
* because we didn't know if client is a superuser.
*/
gucctx = am_superuser ? PGC_SUSET : PGC_BACKEND;
if (MyProcPort != NULL &&
MyProcPort->cmdline_options != NULL)
{
/*
* The maximum possible number of commandline arguments that could
* come from MyProcPort->cmdline_options is (strlen + 1) / 2; see
* pg_split_opts().
*/
char **av;
int maxac;
int ac;
maxac = 2 + (strlen(MyProcPort->cmdline_options) + 1) / 2;
av = (char **) palloc(maxac * sizeof(char *));
ac = 0;
av[ac++] = "postgres";
/* Note this mangles MyProcPort->cmdline_options */
pg_split_opts(av, &ac, MyProcPort->cmdline_options);
av[ac] = NULL;
Assert(ac < maxac);
(void) process_postgres_switches(ac, av, gucctx);
}
/*
* Process any additional GUC variable settings passed in startup packet.
* These are handled exactly like command-line variables.
*/
if (MyProcPort != NULL)
{
ListCell *gucopts = list_head(MyProcPort->guc_options);
while (gucopts)
{
char *name;
char *value;
name = lfirst(gucopts);
gucopts = lnext(gucopts);
value = lfirst(gucopts);
gucopts = lnext(gucopts);
SetConfigOption(name, value, gucctx, PGC_S_CLIENT);
}
}
/* Apply PostAuthDelay as soon as we've read all options */
if (PostAuthDelay > 0)
pg_usleep(PostAuthDelay * 1000000L);
/*
* Initialize various default states that can't be set up until we've
* selected the active user and gotten the right GUC settings.
*/
/* set default namespace search path */
InitializeSearchPath();
/* initialize client encoding */
InitializeClientEncoding();
/* reset the database for walsender */
if (am_walsender)
MyProc->databaseId = MyDatabaseId = InvalidOid;
/* report this backend in the PgBackendStatus array */
if (!bootstrap)
pgstat_bestart();
/* close the transaction we started above */
if (!bootstrap)
CommitTransactionCommand();
}
/*
* PGSharedMemoryCreate
*
* Create a shared memory segment of the given size and initialize its
* standard header. Also, register an on_shmem_exit callback to release
* the storage.
*
* Dead Postgres segments are recycled if found, but we do not fail upon
* collision with non-Postgres shmem segments. The idea here is to detect and
* re-use keys that may have been assigned by a crashed postmaster or backend.
*
* makePrivate means to always create a new segment, rather than attach to
* or recycle any existing segment.
*
* The port number is passed for possible use as a key (for SysV, we use
* it to generate the starting shmem key). In a standalone backend,
* zero will be passed.
*/
PGShmemHeader *
PGSharedMemoryCreate(Size size, bool makePrivate, int port,
PGShmemHeader **shim)
{
IpcMemoryKey NextShmemSegID;
void *memAddress;
PGShmemHeader *hdr;
IpcMemoryId shmid;
struct stat statbuf;
Size sysvsize;
/* Complain if hugepages demanded but we can't possibly support them */
#if !defined(USE_ANONYMOUS_SHMEM) || !defined(MAP_HUGETLB)
if (huge_pages == HUGE_PAGES_ON)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("huge pages not supported on this platform")));
#endif
/* Room for a header? */
Assert(size > MAXALIGN(sizeof(PGShmemHeader)));
#ifdef USE_ANONYMOUS_SHMEM
AnonymousShmem = CreateAnonymousSegment(&size);
AnonymousShmemSize = size;
/* Register on-exit routine to unmap the anonymous segment */
on_shmem_exit(AnonymousShmemDetach, (Datum) 0);
/* Now we need only allocate a minimal-sized SysV shmem block. */
sysvsize = sizeof(PGShmemHeader);
#else
sysvsize = size;
#endif
/* Make sure PGSharedMemoryAttach doesn't fail without need */
UsedShmemSegAddr = NULL;
/* Loop till we find a free IPC key */
NextShmemSegID = port * 1000;
for (NextShmemSegID++;; NextShmemSegID++)
{
/* Try to create new segment */
memAddress = InternalIpcMemoryCreate(NextShmemSegID, sysvsize);
if (memAddress)
break; /* successful create and attach */
/* Check shared memory and possibly remove and recreate */
if (makePrivate) /* a standalone backend shouldn't do this */
continue;
if ((memAddress = PGSharedMemoryAttach(NextShmemSegID, &shmid)) == NULL)
continue; /* can't attach, not one of mine */
/*
* If I am not the creator and it belongs to an extant process,
* continue.
*/
hdr = (PGShmemHeader *) memAddress;
if (hdr->creatorPID != getpid())
{
if (kill(hdr->creatorPID, 0) == 0 || errno != ESRCH)
{
shmdt(memAddress);
continue; /* segment belongs to a live process */
}
}
/*
* The segment appears to be from a dead Postgres process, or from a
* previous cycle of life in this same process. Zap it, if possible,
* and any associated dynamic shared memory segments, as well. This
* probably shouldn't fail, but if it does, assume the segment belongs
* to someone else after all, and continue quietly.
*/
if (hdr->dsm_control != 0)
dsm_cleanup_using_control_segment(hdr->dsm_control);
shmdt(memAddress);
if (shmctl(shmid, IPC_RMID, NULL) < 0)
continue;
/*
* Now try again to create the segment.
*/
memAddress = InternalIpcMemoryCreate(NextShmemSegID, sysvsize);
if (memAddress)
break; /* successful create and attach */
/*
* Can only get here if some other process managed to create the same
* shmem key before we did. Let him have that one, loop around to try
* next key.
*/
}
/*
* OK, we created a new segment. Mark it as created by this process. The
* order of assignments here is critical so that another Postgres process
* can't see the header as valid but belonging to an invalid PID!
*/
hdr = (PGShmemHeader *) memAddress;
hdr->creatorPID = getpid();
hdr->magic = PGShmemMagic;
hdr->dsm_control = 0;
/* Fill in the data directory ID info, too */
if (stat(DataDir, &statbuf) < 0)
ereport(FATAL,
(errcode_for_file_access(),
errmsg("could not stat data directory \"%s\": %m",
DataDir)));
hdr->device = statbuf.st_dev;
hdr->inode = statbuf.st_ino;
/*
* Initialize space allocation status for segment.
*/
hdr->totalsize = size;
hdr->freeoffset = MAXALIGN(sizeof(PGShmemHeader));
*shim = hdr;
/* Save info for possible future use */
UsedShmemSegAddr = memAddress;
UsedShmemSegID = (unsigned long) NextShmemSegID;
/*
* If AnonymousShmem is NULL here, then we're not using anonymous shared
* memory, and should return a pointer to the System V shared memory
* block. Otherwise, the System V shared memory block is only a shim, and
* we must return a pointer to the real block.
*/
#ifdef USE_ANONYMOUS_SHMEM
if (AnonymousShmem == NULL)
return hdr;
memcpy(AnonymousShmem, hdr, sizeof(PGShmemHeader));
return (PGShmemHeader *) AnonymousShmem;
#else
return hdr;
#endif
}
/*
* InitAuxiliaryProcess -- create a per-auxiliary-process data structure
*
* This is called by bgwriter and similar processes so that they will have a
* MyProc value that's real enough to let them wait for LWLocks. The PGPROC
* and sema that are assigned are one of the extra ones created during
* InitProcGlobal.
*
* Auxiliary processes are presently not expected to wait for real (lockmgr)
* locks, so we need not set up the deadlock checker. They are never added
* to the ProcArray or the sinval messaging mechanism, either. They also
* don't get a VXID assigned, since this is only useful when we actually
* hold lockmgr locks.
*
* Startup process however uses locks but never waits for them in the
* normal backend sense. Startup process also takes part in sinval messaging
* as a sendOnly process, so never reads messages from sinval queue. So
* Startup process does have a VXID and does show up in pg_locks.
*/
void
InitAuxiliaryProcess(void)
{
PGPROC *auxproc;
int proctype;
/*
* ProcGlobal should be set up already (if we are a backend, we inherit
* this by fork() or EXEC_BACKEND mechanism from the postmaster).
*/
if (ProcGlobal == NULL || AuxiliaryProcs == NULL)
elog(PANIC, "proc header uninitialized");
if (MyProc != NULL)
elog(ERROR, "you already exist");
/*
* We use the ProcStructLock to protect assignment and releasing of
* AuxiliaryProcs entries.
*
* While we are holding the ProcStructLock, also copy the current shared
* estimate of spins_per_delay to local storage.
*/
SpinLockAcquire(ProcStructLock);
set_spins_per_delay(ProcGlobal->spins_per_delay);
/*
* Find a free auxproc ... *big* trouble if there isn't one ...
*/
for (proctype = 0; proctype < NUM_AUXILIARY_PROCS; proctype++)
{
auxproc = &AuxiliaryProcs[proctype];
if (auxproc->pid == 0)
break;
}
if (proctype >= NUM_AUXILIARY_PROCS)
{
SpinLockRelease(ProcStructLock);
elog(FATAL, "all AuxiliaryProcs are in use");
}
/* Mark auxiliary proc as in use by me */
/* use volatile pointer to prevent code rearrangement */
((volatile PGPROC *) auxproc)->pid = MyProcPid;
MyProc = auxproc;
MyPgXact = &ProcGlobal->allPgXact[auxproc->pgprocno];
SpinLockRelease(ProcStructLock);
/*
* Initialize all fields of MyProc, except for those previously
* initialized by InitProcGlobal.
*/
SHMQueueElemInit(&(MyProc->links));
MyProc->waitStatus = STATUS_OK;
MyProc->lxid = InvalidLocalTransactionId;
MyProc->fpVXIDLock = false;
MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
MyPgXact->xid = InvalidTransactionId;
MyPgXact->xmin = InvalidTransactionId;
MyProc->backendId = InvalidBackendId;
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyPgXact->delayChkpt = false;
MyPgXact->vacuumFlags = 0;
MyProc->lwWaiting = false;
MyProc->lwWaitMode = 0;
MyProc->waitLock = NULL;
MyProc->waitProcLock = NULL;
#ifdef USE_ASSERT_CHECKING
{
int i;
/* Last process should have released all locks. */
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
}
#endif
/*
* Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
* on it. That allows us to repoint the process latch, which so far
* points to process local one, to the shared one.
*/
OwnLatch(&MyProc->procLatch);
SwitchToSharedLatch();
/*
* We might be reusing a semaphore that belonged to a failed process. So
* be careful and reinitialize its value here. (This is not strictly
* necessary anymore, but seems like a good idea for cleanliness.)
*/
PGSemaphoreReset(&MyProc->sem);
/*
* Arrange to clean up at process exit.
*/
on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
}
/*
* InitProcess -- initialize a per-process data structure for this backend
*/
void
InitProcess(void)
{
/* use volatile pointer to prevent code rearrangement */
volatile PROC_HDR *procglobal = ProcGlobal;
/*
* ProcGlobal should be set up already (if we are a backend, we inherit
* this by fork() or EXEC_BACKEND mechanism from the postmaster).
*/
if (procglobal == NULL)
elog(PANIC, "proc header uninitialized");
if (MyProc != NULL)
elog(ERROR, "you already exist");
/*
* Try to get a proc struct from the free list. If this fails, we must be
* out of PGPROC structures (not to mention semaphores).
*
* While we are holding the ProcStructLock, also copy the current shared
* estimate of spins_per_delay to local storage.
*/
SpinLockAcquire(ProcStructLock);
set_spins_per_delay(procglobal->spins_per_delay);
if (IsAnyAutoVacuumProcess())
MyProc = procglobal->autovacFreeProcs;
else if (IsBackgroundWorker)
MyProc = procglobal->bgworkerFreeProcs;
else
MyProc = procglobal->freeProcs;
if (MyProc != NULL)
{
if (IsAnyAutoVacuumProcess())
procglobal->autovacFreeProcs = (PGPROC *) MyProc->links.next;
else if (IsBackgroundWorker)
procglobal->bgworkerFreeProcs = (PGPROC *) MyProc->links.next;
else
procglobal->freeProcs = (PGPROC *) MyProc->links.next;
SpinLockRelease(ProcStructLock);
}
else
{
/*
* If we reach here, all the PGPROCs are in use. This is one of the
* possible places to detect "too many backends", so give the standard
* error message. XXX do we need to give a different failure message
* in the autovacuum case?
*/
SpinLockRelease(ProcStructLock);
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("sorry, too many clients already")));
}
MyPgXact = &ProcGlobal->allPgXact[MyProc->pgprocno];
/*
* Now that we have a PGPROC, mark ourselves as an active postmaster
* child; this is so that the postmaster can detect it if we exit without
* cleaning up. (XXX autovac launcher currently doesn't participate in
* this; it probably should.)
*/
if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
MarkPostmasterChildActive();
/*
* Initialize all fields of MyProc, except for those previously
* initialized by InitProcGlobal.
*/
SHMQueueElemInit(&(MyProc->links));
MyProc->waitStatus = STATUS_OK;
MyProc->lxid = InvalidLocalTransactionId;
MyProc->fpVXIDLock = false;
MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
MyPgXact->xid = InvalidTransactionId;
MyPgXact->xmin = InvalidTransactionId;
MyProc->pid = MyProcPid;
/* backendId, databaseId and roleId will be filled in later */
MyProc->backendId = InvalidBackendId;
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyPgXact->delayChkpt = false;
MyPgXact->vacuumFlags = 0;
/* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
if (IsAutoVacuumWorkerProcess())
MyPgXact->vacuumFlags |= PROC_IS_AUTOVACUUM;
MyProc->lwWaiting = false;
MyProc->lwWaitMode = 0;
MyProc->waitLock = NULL;
MyProc->waitProcLock = NULL;
#ifdef USE_ASSERT_CHECKING
{
int i;
/* Last process should have released all locks. */
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
}
#endif
MyProc->recoveryConflictPending = false;
/* Initialize fields for sync rep */
MyProc->waitLSN = 0;
MyProc->syncRepState = SYNC_REP_NOT_WAITING;
SHMQueueElemInit(&(MyProc->syncRepLinks));
/*
* Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
* on it. That allows us to repoint the process latch, which so far
* points to process local one, to the shared one.
*/
OwnLatch(&MyProc->procLatch);
SwitchToSharedLatch();
/*
* We might be reusing a semaphore that belonged to a failed process. So
* be careful and reinitialize its value here. (This is not strictly
* necessary anymore, but seems like a good idea for cleanliness.)
*/
PGSemaphoreReset(&MyProc->sem);
/*
* Arrange to clean up at backend exit.
*/
on_shmem_exit(ProcKill, 0);
/*
* Now that we have a PGPROC, we could try to acquire locks, so initialize
* local state needed for LWLocks, and the deadlock checker.
*/
InitLWLockAccess();
InitDeadLockChecking();
}
/*
* InternalIpcMemoryCreate(memKey, size)
*
* Attempt to create a new shared memory segment with the specified key.
* Will fail (return NULL) if such a segment already exists. If successful,
* attach the segment to the current process and return its attached address.
* On success, callbacks are registered with on_shmem_exit to detach and
* delete the segment when on_shmem_exit is called.
*
* If we fail with a failure code other than collision-with-existing-segment,
* print out an error and abort. Other types of errors are not recoverable.
*/
static void *
InternalIpcMemoryCreate(IpcMemoryKey memKey, Size size)
{
IpcMemoryId shmid;
void *memAddress;
shmid = shmget(memKey, size, IPC_CREAT | IPC_EXCL | IPCProtection);
if (shmid < 0)
{
int shmget_errno = errno;
/*
* Fail quietly if error indicates a collision with existing segment.
* One would expect EEXIST, given that we said IPC_EXCL, but perhaps
* we could get a permission violation instead? Also, EIDRM might
* occur if an old seg is slated for destruction but not gone yet.
*/
if (shmget_errno == EEXIST || shmget_errno == EACCES
#ifdef EIDRM
|| shmget_errno == EIDRM
#endif
)
return NULL;
/*
* Some BSD-derived kernels are known to return EINVAL, not EEXIST, if
* there is an existing segment but it's smaller than "size" (this is
* a result of poorly-thought-out ordering of error tests). To
* distinguish between collision and invalid size in such cases, we
* make a second try with size = 0. These kernels do not test size
* against SHMMIN in the preexisting-segment case, so we will not get
* EINVAL a second time if there is such a segment.
*/
if (shmget_errno == EINVAL)
{
shmid = shmget(memKey, 0, IPC_CREAT | IPC_EXCL | IPCProtection);
if (shmid < 0)
{
/* As above, fail quietly if we verify a collision */
if (errno == EEXIST || errno == EACCES
#ifdef EIDRM
|| errno == EIDRM
#endif
)
return NULL;
/* Otherwise, fall through to report the original error */
}
else
{
/*
* On most platforms we cannot get here because SHMMIN is
* greater than zero. However, if we do succeed in creating a
* zero-size segment, free it and then fall through to report
* the original error.
*/
if (shmctl(shmid, IPC_RMID, NULL) < 0)
elog(LOG, "shmctl(%d, %d, 0) failed: %m",
(int) shmid, IPC_RMID);
}
}
/*
* Else complain and abort.
*
* Note: at this point EINVAL should mean that either SHMMIN or SHMMAX
* is violated. SHMALL violation might be reported as either ENOMEM
* (BSDen) or ENOSPC (Linux); the Single Unix Spec fails to say which
* it should be. SHMMNI violation is ENOSPC, per spec. Just plain
* not-enough-RAM is ENOMEM.
*/
errno = shmget_errno;
ereport(FATAL,
(errmsg("could not create shared memory segment: %m"),
errdetail("Failed system call was shmget(key=%lu, size=%zu, 0%o).",
(unsigned long) memKey, size,
IPC_CREAT | IPC_EXCL | IPCProtection),
(shmget_errno == EINVAL) ?
errhint("This error usually means that PostgreSQL's request for a shared memory "
"segment exceeded your kernel's SHMMAX parameter, or possibly that "
"it is less than "
"your kernel's SHMMIN parameter.\n"
"The PostgreSQL documentation contains more information about shared "
"memory configuration.") : 0,
(shmget_errno == ENOMEM) ?
errhint("This error usually means that PostgreSQL's request for a shared "
"memory segment exceeded your kernel's SHMALL parameter. You might need "
"to reconfigure the kernel with larger SHMALL.\n"
"The PostgreSQL documentation contains more information about shared "
"memory configuration.") : 0,
(shmget_errno == ENOSPC) ?
errhint("This error does *not* mean that you have run out of disk space. "
"It occurs either if all available shared memory IDs have been taken, "
"in which case you need to raise the SHMMNI parameter in your kernel, "
"or because the system's overall limit for shared memory has been "
"reached.\n"
"The PostgreSQL documentation contains more information about shared "
"memory configuration.") : 0));
}
/* Register on-exit routine to delete the new segment */
on_shmem_exit(IpcMemoryDelete, Int32GetDatum(shmid));
/* OK, should be able to attach to the segment */
memAddress = shmat(shmid, NULL, PG_SHMAT_FLAGS);
if (memAddress == (void *) -1)
elog(FATAL, "shmat(id=%d) failed: %m", shmid);
/* Register on-exit routine to detach new segment before deleting */
on_shmem_exit(IpcMemoryDetach, PointerGetDatum(memAddress));
/*
* Store shmem key and ID in data directory lockfile. Format to try to
* keep it the same length always (trailing junk in the lockfile won't
* hurt, but might confuse humans).
*/
{
char line[64];
sprintf(line, "%9lu %9lu",
(unsigned long) memKey, (unsigned long) shmid);
AddToDataDirLockFile(LOCK_FILE_LINE_SHMEM_KEY, line);
}
return memAddress;
}
/* --------------------------------
* InitPostgres
* Initialize POSTGRES.
*
* The database can be specified by name, using the in_dbname parameter, or by
* OID, using the dboid parameter. In the latter case, the actual database
* name can be returned to the caller in out_dbname. If out_dbname isn't
* NULL, it must point to a buffer of size NAMEDATALEN.
*
* In bootstrap mode no parameters are used.
*
* The return value indicates whether the userID is a superuser. (That
* can only be tested inside a transaction, so we want to do it during
* the startup transaction rather than doing a separate one in postgres.c.)
*
* As of PostgreSQL 8.2, we expect InitProcess() was already called, so we
* already have a PGPROC struct ... but it's not filled in yet.
*
* Note:
* Be very careful with the order of calls in the InitPostgres function.
* --------------------------------
*/
void
InitPostgres(const char *in_dbname, Oid dboid, const char *username,
char *out_dbname)
{
bool bootstrap = IsBootstrapProcessingMode();
bool autovacuum = IsAutoVacuumProcess();
bool am_superuser;
char *fullpath;
char dbname[NAMEDATALEN];
/*
* Add my PGPROC struct to the ProcArray.
*
* Once I have done this, I am visible to other backends!
*/
InitProcessPhase2();
/* Initialize SessionState entry */
SessionState_Init();
/* Initialize memory protection */
GPMemoryProtect_Init();
/*
* Initialize my entry in the shared-invalidation manager's array of
* per-backend data.
*
* Sets up MyBackendId, a unique backend identifier.
*/
MyBackendId = InvalidBackendId;
SharedInvalBackendInit(false);
if (MyBackendId > MaxBackends || MyBackendId <= 0)
elog(FATAL, "bad backend id: %d", MyBackendId);
/* Now that we have a BackendId, we can participate in ProcSignal */
ProcSignalInit(MyBackendId);
/*
* bufmgr needs another initialization call too
*/
InitBufferPoolBackend();
/*
* Initialize local process's access to XLOG. In bootstrap case we may
* skip this since StartupXLOG() was run instead.
*/
if (!bootstrap)
InitXLOGAccess();
/*
* Initialize the relation cache and the system catalog caches. Note that
* no catalog access happens here; we only set up the hashtable structure.
* We must do this before starting a transaction because transaction abort
* would try to touch these hashtables.
*/
RelationCacheInitialize();
InitCatalogCache();
/* Initialize portal manager */
EnablePortalManager();
/* Initialize stats collection --- must happen before first xact */
if (!bootstrap)
pgstat_initialize();
/*
* Load relcache entries for the shared system catalogs. This must create
* at least entries for pg_database and catalogs used for authentication.
*/
RelationCacheInitializePhase2();
/*
* Set up process-exit callback to do pre-shutdown cleanup. This has to
* be after we've initialized all the low-level modules like the buffer
* manager, because during shutdown this has to run before the low-level
* modules start to close down. On the other hand, we want it in place
* before we begin our first transaction --- if we fail during the
* initialization transaction, as is entirely possible, we need the
* AbortTransaction call to clean up.
*/
on_shmem_exit(ShutdownPostgres, 0);
/* TODO: autovacuum launcher should be done here? */
/*
* Start a new transaction here before first access to db, and get a
* snapshot. We don't have a use for the snapshot itself, but we're
* interested in the secondary effect that it sets RecentGlobalXmin.
*/
if (!bootstrap)
{
StartTransactionCommand();
(void) GetTransactionSnapshot();
}
/*
* Figure out our postgres user id, and see if we are a superuser.
*
* In standalone mode and in the autovacuum process, we use a fixed id,
* otherwise we figure it out from the authenticated user name.
*/
if (bootstrap || autovacuum)
{
InitializeSessionUserIdStandalone();
am_superuser = true;
}
else if (!IsUnderPostmaster)
{
InitializeSessionUserIdStandalone();
am_superuser = true;
if (!ThereIsAtLeastOneRole())
ereport(WARNING,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("no roles are defined in this database system"),
errhint("You should immediately run CREATE USER \"%s\" CREATEUSER;.",
username)));
}
else
{
/* normal multiuser case */
Assert(MyProcPort != NULL);
PerformAuthentication(MyProcPort);
InitializeSessionUserId(username);
am_superuser = superuser();
}
/*
* Check a normal user hasn't connected to a superuser reserved slot.
*/
if (!am_superuser &&
ReservedBackends > 0 &&
!HaveNFreeProcs(ReservedBackends))
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("connection limit exceeded for non-superusers"),
errSendAlert(true)));
/*
* If walsender, we don't want to connect to any particular database. Just
* finish the backend startup by processing any options from the startup
* packet, and we're done.
*/
if (am_walsender)
{
Assert(!bootstrap);
/*
* We don't have replication role, which existed in postgres.
*/
if (!superuser())
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser role to start walsender")));
/* process any options passed in the startup packet */
if (MyProcPort != NULL)
process_startup_options(MyProcPort, am_superuser);
/* Apply PostAuthDelay as soon as we've read all options */
if (PostAuthDelay > 0)
pg_usleep(PostAuthDelay * 1000000L);
/* initialize client encoding */
InitializeClientEncoding();
/* report this backend in the PgBackendStatus array */
pgstat_bestart();
/* close the transaction we started above */
CommitTransactionCommand();
return;
}
/*
* Set up the global variables holding database id and path. But note we
* won't actually try to touch the database just yet.
*
* We take a shortcut in the bootstrap case, otherwise we have to look up
* the db name in pg_database.
*/
if (bootstrap)
{
MyDatabaseId = TemplateDbOid;
MyDatabaseTableSpace = DEFAULTTABLESPACE_OID;
}
else if (in_dbname != NULL)
{
HeapTuple tuple;
Form_pg_database dbform;
tuple = GetDatabaseTuple(in_dbname);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", in_dbname)));
dbform = (Form_pg_database) GETSTRUCT(tuple);
MyDatabaseId = HeapTupleGetOid(tuple);
MyDatabaseTableSpace = dbform->dattablespace;
/* take database name from the caller, just for paranoia */
strlcpy(dbname, in_dbname, sizeof(dbname));
pfree(tuple);
}
else
{
/* caller specified database by OID */
HeapTuple tuple;
Form_pg_database dbform;
tuple = GetDatabaseTupleByOid(dboid);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database %u does not exist", dboid)));
dbform = (Form_pg_database) GETSTRUCT(tuple);
MyDatabaseId = HeapTupleGetOid(tuple);
MyDatabaseTableSpace = dbform->dattablespace;
Assert(MyDatabaseId == dboid);
strlcpy(dbname, NameStr(dbform->datname), sizeof(dbname));
/* pass the database name back to the caller */
if (out_dbname)
strcpy(out_dbname, dbname);
pfree(tuple);
}
/* Now we can mark our PGPROC entry with the database ID */
/* (We assume this is an atomic store so no lock is needed) */
MyProc->databaseId = MyDatabaseId;
/*
* Now, take a writer's lock on the database we are trying to connect to.
* If there is a concurrently running DROP DATABASE on that database, this
* will block us until it finishes (and has committed its update of
* pg_database).
*
* Note that the lock is not held long, only until the end of this startup
* transaction. This is OK since we are already advertising our use of
* the database in the PGPROC array; anyone trying a DROP DATABASE after
* this point will see us there.
*
* Note: use of RowExclusiveLock here is reasonable because we envision
* our session as being a concurrent writer of the database. If we had a
* way of declaring a session as being guaranteed-read-only, we could use
* AccessShareLock for such sessions and thereby not conflict against
* CREATE DATABASE.
*/
if (!bootstrap)
LockSharedObject(DatabaseRelationId, MyDatabaseId, 0,
RowExclusiveLock);
/*
* Recheck pg_database to make sure the target database hasn't gone away.
* If there was a concurrent DROP DATABASE, this ensures we will die
* cleanly without creating a mess.
*/
if (!bootstrap)
{
HeapTuple tuple;
tuple = GetDatabaseTuple(dbname);
if (!HeapTupleIsValid(tuple) ||
MyDatabaseId != HeapTupleGetOid(tuple) ||
MyDatabaseTableSpace != ((Form_pg_database) GETSTRUCT(tuple))->dattablespace)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", dbname),
errdetail("It seems to have just been dropped or renamed.")));
}
fullpath = GetDatabasePath(MyDatabaseId, MyDatabaseTableSpace);
if (!bootstrap)
{
if (access(fullpath, F_OK) == -1)
{
if (errno == ENOENT)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist",
dbname),
errdetail("The database subdirectory \"%s\" is missing.",
fullpath)));
else
ereport(FATAL,
(errcode_for_file_access(),
errmsg("could not access directory \"%s\": %m",
fullpath)));
}
ValidatePgVersion(fullpath);
}
SetDatabasePath(fullpath);
/*
* It's now possible to do real access to the system catalogs.
*
* Load relcache entries for the system catalogs. This must create at
* least the minimum set of "nailed-in" cache entries.
*/
RelationCacheInitializePhase3();
/*
* Now we have full access to catalog including toast tables,
* we can process pg_authid.rolconfig. This ought to come before
* processing startup options so that it can override the settings.
*/
if (!bootstrap)
ProcessRoleGUC();
/* set up ACL framework (so CheckMyDatabase can check permissions) */
initialize_acl();
/*
* Re-read the pg_database row for our database, check permissions and set
* up database-specific GUC settings. We can't do this until all the
* database-access infrastructure is up. (Also, it wants to know if the
* user is a superuser, so the above stuff has to happen first.)
*/
if (!bootstrap)
CheckMyDatabase(dbname, am_superuser);
/*
* Now process any command-line switches and any additional GUC variable
* settings passed in the startup packet. We couldn't do this before
* because we didn't know if client is a superuser.
*/
if (MyProcPort != NULL)
process_startup_options(MyProcPort, am_superuser);
/*
* Maintenance Mode: allow superuser to connect when
* gp_maintenance_conn GUC is set. We cannot check it until
* process_startup_options parses the GUC.
*/
if (gp_maintenance_mode && Gp_role == GP_ROLE_DISPATCH &&
!(superuser() && gp_maintenance_conn))
ereport(FATAL,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("maintenance mode: connected by superuser only"),
errSendAlert(false)));
/*
* MPP: If we were started in utility mode then we only want to allow
* incoming sessions that specify gp_session_role=utility as well. This
* lets the bash scripts start the QD in utility mode and connect in but
* protect ourselves from normal clients who might be trying to connect to
* the system while we startup.
*/
if ((Gp_role == GP_ROLE_UTILITY) && (Gp_session_role != GP_ROLE_UTILITY))
{
ereport(FATAL,
(errcode(ERRCODE_CANNOT_CONNECT_NOW),
errmsg("System was started in master-only utility mode - only utility mode connections are allowed")));
}
/* Apply PostAuthDelay as soon as we've read all options */
if (PostAuthDelay > 0)
pg_usleep(PostAuthDelay * 1000000L);
/* set default namespace search path */
InitializeSearchPath();
/* initialize client encoding */
InitializeClientEncoding();
/* report this backend in the PgBackendStatus array */
if (!bootstrap)
pgstat_bestart();
/*
* MPP package setup
*
* Primary function is to establish connctions to the qExecs.
* This is SKIPPED when the database is in bootstrap mode or
* Is not UnderPostmaster.
*/
if (!bootstrap && IsUnderPostmaster)
{
cdb_setup();
on_proc_exit( cdb_cleanup, 0 );
}
/*
* MPP SharedSnapshot Setup
*/
if (Gp_role == GP_ROLE_DISPATCH)
{
addSharedSnapshot("Query Dispatcher", gp_session_id);
}
else if (Gp_role == GP_ROLE_DISPATCHAGENT)
{
SharedLocalSnapshotSlot = NULL;
}
else if (Gp_segment == -1 && Gp_role == GP_ROLE_EXECUTE && !Gp_is_writer)
{
/*
* Entry db singleton QE is a user of the shared snapshot -- not a creator.
* The lookup will occur once the distributed snapshot has been received.
*/
lookupSharedSnapshot("Entry DB Singleton", "Query Dispatcher", gp_session_id);
}
else if (Gp_role == GP_ROLE_EXECUTE)
{
if (Gp_is_writer)
{
addSharedSnapshot("Writer qExec", gp_session_id);
}
else
{
/*
* NOTE: This assumes that the Slot has already been
* allocated by the writer. Need to make sure we
* always allocate the writer qExec first.
*/
lookupSharedSnapshot("Reader qExec", "Writer qExec", gp_session_id);
}
}
/* close the transaction we started above */
if (!bootstrap)
CommitTransactionCommand();
return;
}
