/*
* LockGXact
* Locate the prepared transaction and mark it busy for COMMIT or PREPARE.
*/
static GlobalTransaction
LockGXact(const char *gid, Oid user)
{
int i;
LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
/* Ignore not-yet-valid GIDs */
if (!gxact->valid)
continue;
if (strcmp(gxact->gid, gid) != 0)
continue;
/* Found it, but has someone else got it locked? */
if (TransactionIdIsValid(gxact->locking_xid))
{
if (TransactionIdIsActive(gxact->locking_xid))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("prepared transaction with identifier \"%s\" is busy",
gid)));
gxact->locking_xid = InvalidTransactionId;
}
if (user != gxact->owner && !superuser_arg(user))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied to finish prepared transaction"),
errhint("Must be superuser or the user that prepared the transaction.")));
/* OK for me to lock it */
gxact->locking_xid = GetTopTransactionId();
LWLockRelease(TwoPhaseStateLock);
return gxact;
}
LWLockRelease(TwoPhaseStateLock);
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("prepared transaction with identifier \"%s\" does not exist",
gid)));
/* NOTREACHED */
return NULL;
}
/*
* LockGXact
* Locate the prepared transaction and mark it busy for COMMIT or PREPARE.
*/
static GlobalTransaction
LockGXact(const char *gid, Oid user)
{
int i;
LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
/* Ignore not-yet-valid GIDs */
if (!gxact->valid)
continue;
if (strcmp(gxact->gid, gid) != 0)
continue;
/* Found it, but has someone else got it locked? */
if (TransactionIdIsValid(gxact->locking_xid))
{
if (TransactionIdIsActive(gxact->locking_xid))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("prepared transaction with identifier \"%s\" is busy",
gid)));
gxact->locking_xid = InvalidTransactionId;
}
if (user != gxact->owner && !superuser_arg(user))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied to finish prepared transaction"),
errhint("Must be superuser or the user that prepared the transaction.")));
/*
* Note: it probably would be possible to allow committing from
* another database; but at the moment NOTIFY is known not to work and
* there may be some other issues as well. Hence disallow until
* someone gets motivated to make it work.
*/
if (MyDatabaseId != gxact->proc.databaseId)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("prepared transaction belongs to another database"),
errhint("Connect to the database where the transaction was prepared to finish it.")));
/* OK for me to lock it */
gxact->locking_xid = GetTopTransactionId();
LWLockRelease(TwoPhaseStateLock);
return gxact;
}
LWLockRelease(TwoPhaseStateLock);
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("prepared transaction with identifier \"%s\" does not exist",
gid)));
/* NOTREACHED */
return NULL;
}
/*
* MarkAsPreparing
* Reserve the GID for the given transaction.
*
* Internally, this creates a gxact struct and puts it into the active array.
* NOTE: this is also used when reloading a gxact after a crash; so avoid
* assuming that we can use very much backend context.
*/
GlobalTransaction
MarkAsPreparing(TransactionId xid, const char *gid,
TimestampTz prepared_at, Oid owner, Oid databaseid)
{
GlobalTransaction gxact;
int i;
if (strlen(gid) >= GIDSIZE)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("transaction identifier \"%s\" is too long",
gid)));
/* fail immediately if feature is disabled */
if (max_prepared_xacts == 0)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("prepared transactions are disabled"),
errhint("Set max_prepared_transactions to a nonzero value.")));
LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
/*
* First, find and recycle any gxacts that failed during prepare. We do
* this partly to ensure we don't mistakenly say their GIDs are still
* reserved, and partly so we don't fail on out-of-slots unnecessarily.
*/
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
gxact = TwoPhaseState->prepXacts[i];
if (!gxact->valid && !TransactionIdIsActive(gxact->locking_xid))
{
/* It's dead Jim ... remove from the active array */
TwoPhaseState->numPrepXacts--;
TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
/* and put it back in the freelist */
gxact->proc.links.next = (SHM_QUEUE *) TwoPhaseState->freeGXacts;
TwoPhaseState->freeGXacts = gxact;
/* Back up index count too, so we don't miss scanning one */
i--;
}
}
/* Check for conflicting GID */
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
gxact = TwoPhaseState->prepXacts[i];
if (strcmp(gxact->gid, gid) == 0)
{
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("transaction identifier \"%s\" is already in use",
gid)));
}
}
/* Get a free gxact from the freelist */
if (TwoPhaseState->freeGXacts == NULL)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("maximum number of prepared transactions reached"),
errhint("Increase max_prepared_transactions (currently %d).",
max_prepared_xacts)));
gxact = TwoPhaseState->freeGXacts;
TwoPhaseState->freeGXacts = (GlobalTransaction) gxact->proc.links.next;
/* Initialize it */
MemSet(&gxact->proc, 0, sizeof(PGPROC));
SHMQueueElemInit(&(gxact->proc.links));
gxact->proc.waitStatus = STATUS_OK;
/* We set up the gxact's VXID as InvalidBackendId/XID */
gxact->proc.lxid = (LocalTransactionId) xid;
gxact->proc.xid = xid;
gxact->proc.xmin = InvalidTransactionId;
gxact->proc.pid = 0;
gxact->proc.backendId = InvalidBackendId;
gxact->proc.databaseId = databaseid;
gxact->proc.roleId = owner;
gxact->proc.inCommit = false;
gxact->proc.vacuumFlags = 0;
gxact->proc.lwWaiting = false;
gxact->proc.lwExclusive = false;
gxact->proc.lwWaitLink = NULL;
gxact->proc.waitLock = NULL;
gxact->proc.waitProcLock = NULL;
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
SHMQueueInit(&(gxact->proc.myProcLocks[i]));
/* subxid data must be filled later by GXactLoadSubxactData */
gxact->proc.subxids.overflowed = false;
gxact->proc.subxids.nxids = 0;
gxact->prepared_at = prepared_at;
/* initialize LSN to 0 (start of WAL) */
gxact->prepare_lsn.xlogid = 0;
gxact->prepare_lsn.xrecoff = 0;
gxact->owner = owner;
gxact->locking_xid = xid;
gxact->valid = false;
strcpy(gxact->gid, gid);
/* And insert it into the active array */
Assert(TwoPhaseState->numPrepXacts < max_prepared_xacts);
TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts++] = gxact;
LWLockRelease(TwoPhaseStateLock);
return gxact;
}
