/*
* HeapTupleSatisfiesToast
* True iff heap tuple is valid as a TOAST row.
*
* This is a simplified version that only checks for VACUUM moving conditions.
* It's appropriate for TOAST usage because TOAST really doesn't want to do
* its own time qual checks; if you can see the main table row that contains
* a TOAST reference, you should be able to see the TOASTed value. However,
* vacuuming a TOAST table is independent of the main table, and in case such
* a vacuum fails partway through, we'd better do this much checking.
*
* Among other things, this means you can't do UPDATEs of rows in a TOAST
* table.
*/
bool
HeapTupleSatisfiesToast(HeapTuple htup, Snapshot snapshot,
Buffer buffer)
{
HeapTupleHeader tuple = htup->t_data;
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
if (!HeapTupleHeaderXminCommitted(tuple))
{
if (HeapTupleHeaderXminInvalid(tuple))
return false;
/* Used by pre-9.0 binary upgrades */
if (tuple->t_infomask & HEAP_MOVED_OFF)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (TransactionIdIsCurrentTransactionId(xvac))
return false;
if (!TransactionIdIsInProgress(xvac))
{
if (TransactionIdDidCommit(xvac))
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
}
}
/* Used by pre-9.0 binary upgrades */
else if (tuple->t_infomask & HEAP_MOVED_IN)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (!TransactionIdIsCurrentTransactionId(xvac))
{
if (TransactionIdIsInProgress(xvac))
return false;
if (TransactionIdDidCommit(xvac))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
else
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
}
}
}
/* otherwise assume the tuple is valid for TOAST. */
return true;
}
/*
* HeapTupleIsSurelyDead
*
* Determine whether a tuple is surely dead. We sometimes use this
* in lieu of HeapTupleSatisifesVacuum when the tuple has just been
* tested by HeapTupleSatisfiesMVCC and, therefore, any hint bits that
* can be set should already be set. We assume that if no hint bits
* either for xmin or xmax, the transaction is still running. This is
* therefore faster than HeapTupleSatisfiesVacuum, because we don't
* consult CLOG (and also because we don't need to give an exact answer,
* just whether or not the tuple is surely dead).
*/
bool
HeapTupleIsSurelyDead(HeapTuple htup, TransactionId OldestXmin)
{
HeapTupleHeader tuple = htup->t_data;
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
/*
* If the inserting transaction is marked invalid, then it aborted, and
* the tuple is definitely dead. If it's marked neither committed nor
* invalid, then we assume it's still alive (since the presumption is that
* all relevant hint bits were just set moments ago).
*/
if (!HeapTupleHeaderXminCommitted(tuple))
return HeapTupleHeaderXminInvalid(tuple) ? true : false;
/*
* If the inserting transaction committed, but any deleting transaction
* aborted, the tuple is still alive.
*/
if (tuple->t_infomask & HEAP_XMAX_INVALID)
return false;
/*
* If the XMAX is just a lock, the tuple is still alive.
*/
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return false;
/*
* If the Xmax is a MultiXact, it might be dead or alive, but we cannot
* know without checking pg_multixact.
*/
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
return false;
/* If deleter isn't known to have committed, assume it's still running. */
if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
return false;
/* Deleter committed, so tuple is dead if the XID is old enough. */
return TransactionIdPrecedes(HeapTupleHeaderGetRawXmax(tuple), OldestXmin);
}
/*
* Given a tuple we are about to delete, determine the correct value to store
* into its t_cid field.
*
* If we don't need a combo CID, *cmax is unchanged and *iscombo is set to
* FALSE. If we do need one, *cmax is replaced by a combo CID and *iscombo
* is set to TRUE.
*
* The reason this is separate from the actual HeapTupleHeaderSetCmax()
* operation is that this could fail due to out-of-memory conditions. Hence
* we need to do this before entering the critical section that actually
* changes the tuple in shared buffers.
*/
void
HeapTupleHeaderAdjustCmax(HeapTupleHeader tup,
CommandId *cmax,
bool *iscombo)
{
/*
* If we're marking a tuple deleted that was inserted by (any
* subtransaction of) our transaction, we need to use a combo command id.
* Test for HeapTupleHeaderXminCommitted() first, because it's cheaper than a
* TransactionIdIsCurrentTransactionId call.
*/
if (!HeapTupleHeaderXminCommitted(tup) &&
TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tup)))
{
CommandId cmin = HeapTupleHeaderGetCmin(tup);
*cmax = GetComboCommandId(cmin, *cmax);
*iscombo = true;
}
else
{
*iscombo = false;
}
}
/*
* HeapTupleSatisfiesMVCC
* True iff heap tuple is valid for the given MVCC snapshot.
*
* Here, we consider the effects of:
* all transactions committed as of the time of the given snapshot
* previous commands of this transaction
*
* Does _not_ include:
* transactions shown as in-progress by the snapshot
* transactions started after the snapshot was taken
* changes made by the current command
*
* (Notice, however, that the tuple status hint bits will be updated on the
* basis of the true state of the transaction, even if we then pretend we
* can't see it.)
*/
bool
HeapTupleSatisfiesMVCC(HeapTuple htup, Snapshot snapshot,
Buffer buffer)
{
HeapTupleHeader tuple = htup->t_data;
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
if (!HeapTupleHeaderXminCommitted(tuple))
{
if (HeapTupleHeaderXminInvalid(tuple))
return false;
/* Used by pre-9.0 binary upgrades */
if (tuple->t_infomask & HEAP_MOVED_OFF)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (TransactionIdIsCurrentTransactionId(xvac))
return false;
if (!TransactionIdIsInProgress(xvac))
{
if (TransactionIdDidCommit(xvac))
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
}
}
/* Used by pre-9.0 binary upgrades */
else if (tuple->t_infomask & HEAP_MOVED_IN)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (!TransactionIdIsCurrentTransactionId(xvac))
{
if (TransactionIdIsInProgress(xvac))
return false;
if (TransactionIdDidCommit(xvac))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
else
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
}
}
else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
{
if (HeapTupleHeaderGetCmin(tuple) >= snapshot->curcid)
return false; /* inserted after scan started */
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid */
return true;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask)) /* not deleter */
return true;
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
/* updating subtransaction must have aborted */
if (!TransactionIdIsCurrentTransactionId(xmax))
return true;
else if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
return true; /* updated after scan started */
else
return false; /* updated before scan started */
}
if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
{
/* deleting subtransaction must have aborted */
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return true;
}
if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
return true; /* deleted after scan started */
else
return false; /* deleted before scan started */
}
else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
return false;
else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
HeapTupleHeaderGetRawXmin(tuple));
else
{
/* it must have aborted or crashed */
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
}
/*
* By here, the inserting transaction has committed - have to check
* when...
*/
if (!HeapTupleHeaderXminFrozen(tuple)
&& XidInMVCCSnapshot(HeapTupleHeaderGetRawXmin(tuple), snapshot))
return false; /* treat as still in progress */
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid or aborted */
return true;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
/* already checked above */
Assert(!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask));
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
if (TransactionIdIsCurrentTransactionId(xmax))
{
if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
return true; /* deleted after scan started */
else
return false; /* deleted before scan started */
}
if (TransactionIdIsInProgress(xmax))
return true;
if (TransactionIdDidCommit(xmax))
{
/* updating transaction committed, but when? */
if (XidInMVCCSnapshot(xmax, snapshot))
return true; /* treat as still in progress */
return false;
}
/* it must have aborted or crashed */
return true;
}
if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
{
if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
{
if (HeapTupleHeaderGetCmax(tuple) >= snapshot->curcid)
return true; /* deleted after scan started */
else
return false; /* deleted before scan started */
}
if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
return true;
if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
{
/* it must have aborted or crashed */
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return true;
}
/* xmax transaction committed */
SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
HeapTupleHeaderGetRawXmax(tuple));
}
/*
* OK, the deleting transaction committed too ... but when?
*/
if (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmax(tuple), snapshot))
return true; /* treat as still in progress */
return false;
}
/*
* HeapTupleSatisfiesDirty
* True iff heap tuple is valid including effects of open transactions.
*
* Here, we consider the effects of:
* all committed and in-progress transactions (as of the current instant)
* previous commands of this transaction
* changes made by the current command
*
* This is essentially like HeapTupleSatisfiesSelf as far as effects of
* the current transaction and committed/aborted xacts are concerned.
* However, we also include the effects of other xacts still in progress.
*
* A special hack is that the passed-in snapshot struct is used as an
* output argument to return the xids of concurrent xacts that affected the
* tuple. snapshot->xmin is set to the tuple's xmin if that is another
* transaction that's still in progress; or to InvalidTransactionId if the
* tuple's xmin is committed good, committed dead, or my own xact. Similarly
* for snapshot->xmax and the tuple's xmax.
*/
bool
HeapTupleSatisfiesDirty(HeapTuple htup, Snapshot snapshot,
Buffer buffer)
{
HeapTupleHeader tuple = htup->t_data;
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
snapshot->xmin = snapshot->xmax = InvalidTransactionId;
if (!HeapTupleHeaderXminCommitted(tuple))
{
if (HeapTupleHeaderXminInvalid(tuple))
return false;
/* Used by pre-9.0 binary upgrades */
if (tuple->t_infomask & HEAP_MOVED_OFF)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (TransactionIdIsCurrentTransactionId(xvac))
return false;
if (!TransactionIdIsInProgress(xvac))
{
if (TransactionIdDidCommit(xvac))
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
}
}
/* Used by pre-9.0 binary upgrades */
else if (tuple->t_infomask & HEAP_MOVED_IN)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (!TransactionIdIsCurrentTransactionId(xvac))
{
if (TransactionIdIsInProgress(xvac))
return false;
if (TransactionIdDidCommit(xvac))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
else
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
}
}
else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
{
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid */
return true;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask)) /* not deleter */
return true;
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
/* updating subtransaction must have aborted */
if (!TransactionIdIsCurrentTransactionId(xmax))
return true;
else
return false;
}
if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
{
/* deleting subtransaction must have aborted */
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return true;
}
return false;
}
else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
{
snapshot->xmin = HeapTupleHeaderGetRawXmin(tuple);
/* XXX shouldn't we fall through to look at xmax? */
return true; /* in insertion by other */
}
else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
HeapTupleHeaderGetRawXmin(tuple));
else
{
/* it must have aborted or crashed */
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return false;
}
}
/* by here, the inserting transaction has committed */
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid or aborted */
return true;
if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
{
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
return false; /* updated by other */
}
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
if (TransactionIdIsCurrentTransactionId(xmax))
return false;
if (TransactionIdIsInProgress(xmax))
{
snapshot->xmax = xmax;
return true;
}
if (TransactionIdDidCommit(xmax))
return false;
/* it must have aborted or crashed */
return true;
}
if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
{
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
return false;
}
if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
{
if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
snapshot->xmax = HeapTupleHeaderGetRawXmax(tuple);
return true;
}
if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
{
/* it must have aborted or crashed */
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return true;
}
/* xmax transaction committed */
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
{
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return true;
}
SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
HeapTupleHeaderGetRawXmax(tuple));
return false; /* updated by other */
}
/*
* HeapTupleSatisfiesUpdate
*
* This function returns a more detailed result code than most of the
* functions in this file, since UPDATE needs to know more than "is it
* visible?". It also allows for user-supplied CommandId rather than
* relying on CurrentCommandId.
*
* The possible return codes are:
*
* HeapTupleInvisible: the tuple didn't exist at all when the scan started,
* e.g. it was created by a later CommandId.
*
* HeapTupleMayBeUpdated: The tuple is valid and visible, so it may be
* updated.
*
* HeapTupleSelfUpdated: The tuple was updated by the current transaction,
* after the current scan started.
*
* HeapTupleUpdated: The tuple was updated by a committed transaction.
*
* HeapTupleBeingUpdated: The tuple is being updated by an in-progress
* transaction other than the current transaction. (Note: this includes
* the case where the tuple is share-locked by a MultiXact, even if the
* MultiXact includes the current transaction. Callers that want to
* distinguish that case must test for it themselves.)
*/
HTSU_Result
HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
Buffer buffer)
{
HeapTupleHeader tuple = htup->t_data;
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
if (!HeapTupleHeaderXminCommitted(tuple))
{
if (HeapTupleHeaderXminInvalid(tuple))
return HeapTupleInvisible;
/* Used by pre-9.0 binary upgrades */
if (tuple->t_infomask & HEAP_MOVED_OFF)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (TransactionIdIsCurrentTransactionId(xvac))
return HeapTupleInvisible;
if (!TransactionIdIsInProgress(xvac))
{
if (TransactionIdDidCommit(xvac))
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return HeapTupleInvisible;
}
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
}
}
/* Used by pre-9.0 binary upgrades */
else if (tuple->t_infomask & HEAP_MOVED_IN)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (!TransactionIdIsCurrentTransactionId(xvac))
{
if (TransactionIdIsInProgress(xvac))
return HeapTupleInvisible;
if (TransactionIdDidCommit(xvac))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
else
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return HeapTupleInvisible;
}
}
}
else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
{
if (HeapTupleHeaderGetCmin(tuple) >= curcid)
return HeapTupleInvisible; /* inserted after scan started */
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid */
return HeapTupleMayBeUpdated;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
{
TransactionId xmax;
xmax = HeapTupleHeaderGetRawXmax(tuple);
/*
* Careful here: even though this tuple was created by our own
* transaction, it might be locked by other transactions, if
* the original version was key-share locked when we updated
* it.
*/
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
if (MultiXactHasRunningRemoteMembers(xmax))
return HeapTupleBeingUpdated;
else
return HeapTupleMayBeUpdated;
}
/* if locker is gone, all's well */
if (!TransactionIdIsInProgress(xmax))
return HeapTupleMayBeUpdated;
if (!TransactionIdIsCurrentTransactionId(xmax))
return HeapTupleBeingUpdated;
else
return HeapTupleMayBeUpdated;
}
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
/* updating subtransaction must have aborted */
if (!TransactionIdIsCurrentTransactionId(xmax))
{
if (MultiXactHasRunningRemoteMembers(HeapTupleHeaderGetRawXmax(tuple)))
return HeapTupleBeingUpdated;
return HeapTupleMayBeUpdated;
}
else
{
if (HeapTupleHeaderGetCmax(tuple) >= curcid)
return HeapTupleSelfUpdated; /* updated after scan
* started */
else
return HeapTupleInvisible; /* updated before scan
* started */
}
}
if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
{
/* deleting subtransaction must have aborted */
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return HeapTupleMayBeUpdated;
}
if (HeapTupleHeaderGetCmax(tuple) >= curcid)
return HeapTupleSelfUpdated; /* updated after scan started */
else
return HeapTupleInvisible; /* updated before scan started */
}
else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
return HeapTupleInvisible;
else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
HeapTupleHeaderGetRawXmin(tuple));
else
{
/* it must have aborted or crashed */
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return HeapTupleInvisible;
}
}
/* by here, the inserting transaction has committed */
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid or aborted */
return HeapTupleMayBeUpdated;
if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
{
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return HeapTupleMayBeUpdated;
return HeapTupleUpdated; /* updated by other */
}
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
{
/*
* If it's only locked but neither EXCL_LOCK nor KEYSHR_LOCK is
* set, it cannot possibly be running. Otherwise need to check.
*/
if ((tuple->t_infomask & (HEAP_XMAX_EXCL_LOCK |
HEAP_XMAX_KEYSHR_LOCK)) &&
MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
return HeapTupleBeingUpdated;
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);
return HeapTupleMayBeUpdated;
}
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
if (TransactionIdIsCurrentTransactionId(xmax))
{
if (HeapTupleHeaderGetCmax(tuple) >= curcid)
return HeapTupleSelfUpdated; /* updated after scan started */
else
return HeapTupleInvisible; /* updated before scan started */
}
if (TransactionIdIsInProgress(xmax))
return HeapTupleBeingUpdated;
if (TransactionIdDidCommit(xmax))
return HeapTupleUpdated;
/*
* By here, the update in the Xmax is either aborted or crashed, but
* what about the other members?
*/
if (!MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
{
/*
* There's no member, even just a locker, alive anymore, so we can
* mark the Xmax as invalid.
*/
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return HeapTupleMayBeUpdated;
}
else
{
/* There are lockers running */
return HeapTupleBeingUpdated;
}
}
if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
{
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return HeapTupleMayBeUpdated;
if (HeapTupleHeaderGetCmax(tuple) >= curcid)
return HeapTupleSelfUpdated; /* updated after scan started */
else
return HeapTupleInvisible; /* updated before scan started */
}
if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
return HeapTupleBeingUpdated;
if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
{
/* it must have aborted or crashed */
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return HeapTupleMayBeUpdated;
}
/* xmax transaction committed */
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
{
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return HeapTupleMayBeUpdated;
}
SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
HeapTupleHeaderGetRawXmax(tuple));
return HeapTupleUpdated; /* updated by other */
}
/*
* See the comments for HeapTupleSatisfiesMVCC for the semantics this function
* obeys.
*
* Only usable on tuples from catalog tables!
*
* We don't need to support HEAP_MOVED_(IN|OFF) for now because we only support
* reading catalog pages which couldn't have been created in an older version.
*
* We don't set any hint bits in here as it seems unlikely to be beneficial as
* those should already be set by normal access and it seems to be too
* dangerous to do so as the semantics of doing so during timetravel are more
* complicated than when dealing "only" with the present.
*/
bool
HeapTupleSatisfiesHistoricMVCC(HeapTuple htup, Snapshot snapshot,
Buffer buffer)
{
HeapTupleHeader tuple = htup->t_data;
TransactionId xmin = HeapTupleHeaderGetXmin(tuple);
TransactionId xmax = HeapTupleHeaderGetRawXmax(tuple);
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
/* inserting transaction aborted */
if (HeapTupleHeaderXminInvalid(tuple))
{
Assert(!TransactionIdDidCommit(xmin));
return false;
}
/* check if it's one of our txids, toplevel is also in there */
else if (TransactionIdInArray(xmin, snapshot->subxip, snapshot->subxcnt))
{
bool resolved;
CommandId cmin = HeapTupleHeaderGetRawCommandId(tuple);
CommandId cmax = InvalidCommandId;
/*
* another transaction might have (tried to) delete this tuple or
* cmin/cmax was stored in a combocid. So we need to lookup the actual
* values externally.
*/
resolved = ResolveCminCmaxDuringDecoding(HistoricSnapshotGetTupleCids(), snapshot,
htup, buffer,
&cmin, &cmax);
if (!resolved)
elog(ERROR, "could not resolve cmin/cmax of catalog tuple");
Assert(cmin != InvalidCommandId);
if (cmin >= snapshot->curcid)
return false; /* inserted after scan started */
/* fall through */
}
/* committed before our xmin horizon. Do a normal visibility check. */
else if (TransactionIdPrecedes(xmin, snapshot->xmin))
{
Assert(!(HeapTupleHeaderXminCommitted(tuple) &&
!TransactionIdDidCommit(xmin)));
/* check for hint bit first, consult clog afterwards */
if (!HeapTupleHeaderXminCommitted(tuple) &&
!TransactionIdDidCommit(xmin))
return false;
/* fall through */
}
/* beyond our xmax horizon, i.e. invisible */
else if (TransactionIdFollowsOrEquals(xmin, snapshot->xmax))
{
return false;
}
/* check if it's a committed transaction in [xmin, xmax) */
else if (TransactionIdInArray(xmin, snapshot->xip, snapshot->xcnt))
{
/* fall through */
}
/*
* none of the above, i.e. between [xmin, xmax) but hasn't committed. I.e.
* invisible.
*/
else
{
return false;
}
/* at this point we know xmin is visible, go on to check xmax */
/* xid invalid or aborted */
if (tuple->t_infomask & HEAP_XMAX_INVALID)
return true;
/* locked tuples are always visible */
else if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
return true;
/*
* We can see multis here if we're looking at user tables or if somebody
* SELECT ... FOR SHARE/UPDATE a system table.
*/
else if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
xmax = HeapTupleGetUpdateXid(tuple);
}
/* check if it's one of our txids, toplevel is also in there */
if (TransactionIdInArray(xmax, snapshot->subxip, snapshot->subxcnt))
{
bool resolved;
CommandId cmin;
CommandId cmax = HeapTupleHeaderGetRawCommandId(tuple);
/* Lookup actual cmin/cmax values */
resolved = ResolveCminCmaxDuringDecoding(HistoricSnapshotGetTupleCids(), snapshot,
htup, buffer,
&cmin, &cmax);
if (!resolved)
elog(ERROR, "could not resolve combocid to cmax");
Assert(cmax != InvalidCommandId);
if (cmax >= snapshot->curcid)
return true; /* deleted after scan started */
else
return false; /* deleted before scan started */
}
/* below xmin horizon, normal transaction state is valid */
else if (TransactionIdPrecedes(xmax, snapshot->xmin))
{
Assert(!(tuple->t_infomask & HEAP_XMAX_COMMITTED &&
!TransactionIdDidCommit(xmax)));
/* check hint bit first */
if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
return false;
/* check clog */
return !TransactionIdDidCommit(xmax);
}
/* above xmax horizon, we cannot possibly see the deleting transaction */
else if (TransactionIdFollowsOrEquals(xmax, snapshot->xmax))
return true;
/* xmax is between [xmin, xmax), check known committed array */
else if (TransactionIdInArray(xmax, snapshot->xip, snapshot->xcnt))
return false;
/* xmax is between [xmin, xmax), but known not to have committed yet */
else
return true;
}
/*
* HeapTupleSatisfiesVacuum
*
* Determine the status of tuples for VACUUM purposes. Here, what
* we mainly want to know is if a tuple is potentially visible to *any*
* running transaction. If so, it can't be removed yet by VACUUM.
*
* OldestXmin is a cutoff XID (obtained from GetOldestXmin()). Tuples
* deleted by XIDs >= OldestXmin are deemed "recently dead"; they might
* still be visible to some open transaction, so we can't remove them,
* even if we see that the deleting transaction has committed.
*/
HTSV_Result
HeapTupleSatisfiesVacuum(HeapTuple htup, TransactionId OldestXmin,
Buffer buffer)
{
HeapTupleHeader tuple = htup->t_data;
Assert(ItemPointerIsValid(&htup->t_self));
Assert(htup->t_tableOid != InvalidOid);
/*
* Has inserting transaction committed?
*
* If the inserting transaction aborted, then the tuple was never visible
* to any other transaction, so we can delete it immediately.
*/
if (!HeapTupleHeaderXminCommitted(tuple))
{
if (HeapTupleHeaderXminInvalid(tuple))
return HEAPTUPLE_DEAD;
/* Used by pre-9.0 binary upgrades */
else if (tuple->t_infomask & HEAP_MOVED_OFF)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (TransactionIdIsCurrentTransactionId(xvac))
return HEAPTUPLE_DELETE_IN_PROGRESS;
if (TransactionIdIsInProgress(xvac))
return HEAPTUPLE_DELETE_IN_PROGRESS;
if (TransactionIdDidCommit(xvac))
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return HEAPTUPLE_DEAD;
}
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
}
/* Used by pre-9.0 binary upgrades */
else if (tuple->t_infomask & HEAP_MOVED_IN)
{
TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
if (TransactionIdIsCurrentTransactionId(xvac))
return HEAPTUPLE_INSERT_IN_PROGRESS;
if (TransactionIdIsInProgress(xvac))
return HEAPTUPLE_INSERT_IN_PROGRESS;
if (TransactionIdDidCommit(xvac))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
InvalidTransactionId);
else
{
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return HEAPTUPLE_DEAD;
}
}
else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
{
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid */
return HEAPTUPLE_INSERT_IN_PROGRESS;
/* only locked? run infomask-only check first, for performance */
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask) ||
HeapTupleHeaderIsOnlyLocked(tuple))
return HEAPTUPLE_INSERT_IN_PROGRESS;
/* inserted and then deleted by same xact */
return HEAPTUPLE_DELETE_IN_PROGRESS;
}
else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
HeapTupleHeaderGetRawXmin(tuple));
else
{
/*
* Not in Progress, Not Committed, so either Aborted or crashed
*/
SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
InvalidTransactionId);
return HEAPTUPLE_DEAD;
}
/*
* At this point the xmin is known committed, but we might not have
* been able to set the hint bit yet; so we can no longer Assert that
* it's set.
*/
}
/*
* Okay, the inserter committed, so it was good at some point. Now what
* about the deleting transaction?
*/
if (tuple->t_infomask & HEAP_XMAX_INVALID)
return HEAPTUPLE_LIVE;
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
{
/*
* "Deleting" xact really only locked it, so the tuple is live in any
* case. However, we should make sure that either XMAX_COMMITTED or
* XMAX_INVALID gets set once the xact is gone, to reduce the costs of
* examining the tuple for future xacts. Also, marking dead
* MultiXacts as invalid here provides defense against MultiXactId
* wraparound (see also comments in heap_freeze_tuple()).
*/
if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
{
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
/*
* If it's only locked but neither EXCL_LOCK nor KEYSHR_LOCK
* are set, it cannot possibly be running; otherwise have to
* check.
*/
if ((tuple->t_infomask & (HEAP_XMAX_EXCL_LOCK |
HEAP_XMAX_KEYSHR_LOCK)) &&
MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
return HEAPTUPLE_LIVE;
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);
}
else
{
if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
return HEAPTUPLE_LIVE;
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
}
}
/*
* We don't really care whether xmax did commit, abort or crash. We
* know that xmax did lock the tuple, but it did not and will never
* actually update it.
*/
return HEAPTUPLE_LIVE;
}
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId xmax;
if (MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple)))
{
/* already checked above */
Assert(!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask));
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
if (TransactionIdIsInProgress(xmax))
return HEAPTUPLE_DELETE_IN_PROGRESS;
else if (TransactionIdDidCommit(xmax))
/* there are still lockers around -- can't return DEAD here */
return HEAPTUPLE_RECENTLY_DEAD;
/* updating transaction aborted */
return HEAPTUPLE_LIVE;
}
Assert(!(tuple->t_infomask & HEAP_XMAX_COMMITTED));
xmax = HeapTupleGetUpdateXid(tuple);
/* not LOCKED_ONLY, so it has to have an xmax */
Assert(TransactionIdIsValid(xmax));
/* multi is not running -- updating xact cannot be */
Assert(!TransactionIdIsInProgress(xmax));
if (TransactionIdDidCommit(xmax))
{
if (!TransactionIdPrecedes(xmax, OldestXmin))
return HEAPTUPLE_RECENTLY_DEAD;
else
return HEAPTUPLE_DEAD;
}
/*
* Not in Progress, Not Committed, so either Aborted or crashed.
* Remove the Xmax.
*/
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);
return HEAPTUPLE_LIVE;
}
if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
{
if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
return HEAPTUPLE_DELETE_IN_PROGRESS;
else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
HeapTupleHeaderGetRawXmax(tuple));
else
{
/*
* Not in Progress, Not Committed, so either Aborted or crashed
*/
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
return HEAPTUPLE_LIVE;
}
/*
* At this point the xmax is known committed, but we might not have
* been able to set the hint bit yet; so we can no longer Assert that
* it's set.
*/
}
/*
* Deleter committed, but perhaps it was recent enough that some open
* transactions could still see the tuple.
*/
if (!TransactionIdPrecedes(HeapTupleHeaderGetRawXmax(tuple), OldestXmin))
return HEAPTUPLE_RECENTLY_DEAD;
/* Otherwise, it's dead and removable */
return HEAPTUPLE_DEAD;
}
/*
* Disallow use of an uncommitted pg_enum tuple.
*
* We need to make sure that uncommitted enum values don't get into indexes.
* If they did, and if we then rolled back the pg_enum addition, we'd have
* broken the index because value comparisons will not work reliably without
* an underlying pg_enum entry. (Note that removal of the heap entry
* containing an enum value is not sufficient to ensure that it doesn't appear
* in upper levels of indexes.) To do this we prevent an uncommitted row from
* being used for any SQL-level purpose. This is stronger than necessary,
* since the value might not be getting inserted into a table or there might
* be no index on its column, but it's easy to enforce centrally.
*
* However, it's okay to allow use of uncommitted values belonging to enum
* types that were themselves created in the same transaction, because then
* any such index would also be new and would go away altogether on rollback.
* (This case is required by pg_upgrade.)
*
* This function needs to be called (directly or indirectly) in any of the
* functions below that could return an enum value to SQL operations.
*/
static void
check_safe_enum_use(HeapTuple enumval_tup)
{
TransactionId xmin;
Form_pg_enum en;
HeapTuple enumtyp_tup;
/*
* If the row is hinted as committed, it's surely safe. This provides a
* fast path for all normal use-cases.
*/
if (HeapTupleHeaderXminCommitted(enumval_tup->t_data))
return;
/*
* Usually, a row would get hinted as committed when it's read or loaded
* into syscache; but just in case not, let's check the xmin directly.
*/
xmin = HeapTupleHeaderGetXmin(enumval_tup->t_data);
if (!TransactionIdIsInProgress(xmin) &&
TransactionIdDidCommit(xmin))
return;
/* It is a new enum value, so check to see if the whole enum is new */
en = (Form_pg_enum) GETSTRUCT(enumval_tup);
enumtyp_tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(en->enumtypid));
if (!HeapTupleIsValid(enumtyp_tup))
elog(ERROR, "cache lookup failed for type %u", en->enumtypid);
/*
* We insist that the type have been created in the same (sub)transaction
* as the enum value. It would be safe to allow the type's originating
* xact to be a subcommitted child of the enum value's xact, but not vice
* versa (since we might now be in a subxact of the type's originating
* xact, which could roll back along with the enum value's subxact). The
* former case seems a sufficiently weird usage pattern as to not be worth
* spending code for, so we're left with a simple equality check.
*
* We also insist that the type's pg_type row not be HEAP_UPDATED. If it
* is, we can't tell whether the row was created or only modified in the
* apparent originating xact, so it might be older than that xact. (We do
* not worry whether the enum value is HEAP_UPDATED; if it is, we might
* think it's too new and throw an unnecessary error, but we won't allow
* an unsafe case.)
*/
if (xmin == HeapTupleHeaderGetXmin(enumtyp_tup->t_data) &&
!(enumtyp_tup->t_data->t_infomask & HEAP_UPDATED))
{
/* same (sub)transaction, so safe */
ReleaseSysCache(enumtyp_tup);
return;
}
/*
* There might well be other tests we could do here to narrow down the
* unsafe conditions, but for now just raise an exception.
*/
ereport(ERROR,
(errcode(ERRCODE_UNSAFE_NEW_ENUM_VALUE_USAGE),
errmsg("unsafe use of new value \"%s\" of enum type %s",
NameStr(en->enumlabel),
format_type_be(en->enumtypid)),
errhint("New enum values must be committed before they can be used.")));
}
