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Up to now async.c has used TransactionIdIsInProgress() to detect whether a notify message's source transaction is still running. However, that function has a quick-exit path that reports that XIDs before RecentXmin are no longer running. If a listening backend is doing nothing but listening, and not running any queries, there is nothing that will advance its value of RecentXmin. Once 2 billion transactions elapse, the RecentXmin check causes active transactions to be reported as not running. If they aren't committed yet according to CLOG, async.c decides they aborted and discards their messages. The timing for that is a bit tight but it can happen when multiple backends are sending notifies concurrently. The net symptom therefore is that a sufficiently-long-surviving listen-only backend starts to miss some fraction of NOTIFY traffic, but only under heavy load. The only function that updates RecentXmin is GetSnapshotData(). A brute-force fix would therefore be to take a snapshot before processing incoming notify messages. But that would add cycles, as well as contention for the ProcArrayLock. We can be smarter: having taken the snapshot, let's use that to check for running XIDs, and not call TransactionIdIsInProgress() at all. In this way we reduce the number of ProcArrayLock acquisitions from one per message to one per notify interrupt; that's the same under light load but should be a benefit under heavy load. Light testing says that this change is a wash performance-wise for normal loads. I looked around for other callers of TransactionIdIsInProgress() that might be at similar risk, and didn't find any; all of them are inside transactions that presumably have already taken a snapshot. Problem report and diagnosis by Marko Tiikkaja, patch by me. Back-patch to all supported branches, since it's been like this since 9.0. Discussion: https://postgr.es/m/20170926182935.14128.65278@wrigleys.postgresql.org
1808 lines
53 KiB
C
1808 lines
53 KiB
C
/*-------------------------------------------------------------------------
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*
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* tqual.c
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* POSTGRES "time qualification" code, ie, tuple visibility rules.
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*
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* NOTE: all the HeapTupleSatisfies routines will update the tuple's
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* "hint" status bits if we see that the inserting or deleting transaction
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* has now committed or aborted (and it is safe to set the hint bits).
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* If the hint bits are changed, MarkBufferDirtyHint is called on
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* the passed-in buffer. The caller must hold not only a pin, but at least
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* shared buffer content lock on the buffer containing the tuple.
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*
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* NOTE: When using a non-MVCC snapshot, we must check
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* TransactionIdIsInProgress (which looks in the PGXACT array)
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* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
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* pg_xact). Otherwise we have a race condition: we might decide that a
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* just-committed transaction crashed, because none of the tests succeed.
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* xact.c is careful to record commit/abort in pg_xact before it unsets
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* MyPgXact->xid in the PGXACT array. That fixes that problem, but it
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* also means there is a window where TransactionIdIsInProgress and
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* TransactionIdDidCommit will both return true. If we check only
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* TransactionIdDidCommit, we could consider a tuple committed when a
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* later GetSnapshotData call will still think the originating transaction
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* is in progress, which leads to application-level inconsistency. The
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* upshot is that we gotta check TransactionIdIsInProgress first in all
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* code paths, except for a few cases where we are looking at
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* subtransactions of our own main transaction and so there can't be any
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* race condition.
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*
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* When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
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* TransactionIdIsInProgress, but the logic is otherwise the same: do not
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* check pg_xact until after deciding that the xact is no longer in progress.
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*
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*
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* Summary of visibility functions:
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*
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* HeapTupleSatisfiesMVCC()
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* visible to supplied snapshot, excludes current command
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* HeapTupleSatisfiesUpdate()
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* visible to instant snapshot, with user-supplied command
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* counter and more complex result
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* HeapTupleSatisfiesSelf()
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* visible to instant snapshot and current command
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* HeapTupleSatisfiesDirty()
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* like HeapTupleSatisfiesSelf(), but includes open transactions
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* HeapTupleSatisfiesVacuum()
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* visible to any running transaction, used by VACUUM
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* HeapTupleSatisfiesNonVacuumable()
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* Snapshot-style API for HeapTupleSatisfiesVacuum
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* HeapTupleSatisfiesToast()
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* visible unless part of interrupted vacuum, used for TOAST
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* HeapTupleSatisfiesAny()
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* all tuples are visible
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/backend/utils/time/tqual.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/htup_details.h"
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#include "access/multixact.h"
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#include "access/subtrans.h"
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#include "access/transam.h"
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#include "access/xact.h"
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#include "access/xlog.h"
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#include "storage/bufmgr.h"
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#include "storage/procarray.h"
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#include "utils/builtins.h"
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#include "utils/combocid.h"
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#include "utils/snapmgr.h"
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#include "utils/tqual.h"
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/* Static variables representing various special snapshot semantics */
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SnapshotData SnapshotSelfData = {HeapTupleSatisfiesSelf};
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SnapshotData SnapshotAnyData = {HeapTupleSatisfiesAny};
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/*
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* SetHintBits()
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*
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* Set commit/abort hint bits on a tuple, if appropriate at this time.
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*
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* It is only safe to set a transaction-committed hint bit if we know the
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* transaction's commit record is guaranteed to be flushed to disk before the
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* buffer, or if the table is temporary or unlogged and will be obliterated by
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* a crash anyway. We cannot change the LSN of the page here, because we may
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* hold only a share lock on the buffer, so we can only use the LSN to
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* interlock this if the buffer's LSN already is newer than the commit LSN;
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* otherwise we have to just refrain from setting the hint bit until some
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* future re-examination of the tuple.
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*
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* We can always set hint bits when marking a transaction aborted. (Some
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* code in heapam.c relies on that!)
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*
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* Also, if we are cleaning up HEAP_MOVED_IN or HEAP_MOVED_OFF entries, then
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* we can always set the hint bits, since pre-9.0 VACUUM FULL always used
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* synchronous commits and didn't move tuples that weren't previously
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* hinted. (This is not known by this subroutine, but is applied by its
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* callers.) Note: old-style VACUUM FULL is gone, but we have to keep this
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* module's support for MOVED_OFF/MOVED_IN flag bits for as long as we
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* support in-place update from pre-9.0 databases.
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*
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* Normal commits may be asynchronous, so for those we need to get the LSN
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* of the transaction and then check whether this is flushed.
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*
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* The caller should pass xid as the XID of the transaction to check, or
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* InvalidTransactionId if no check is needed.
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*/
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static inline void
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SetHintBits(HeapTupleHeader tuple, Buffer buffer,
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uint16 infomask, TransactionId xid)
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{
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if (TransactionIdIsValid(xid))
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{
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/* NB: xid must be known committed here! */
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XLogRecPtr commitLSN = TransactionIdGetCommitLSN(xid);
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if (BufferIsPermanent(buffer) && XLogNeedsFlush(commitLSN) &&
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BufferGetLSNAtomic(buffer) < commitLSN)
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{
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/* not flushed and no LSN interlock, so don't set hint */
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return;
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}
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}
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tuple->t_infomask |= infomask;
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MarkBufferDirtyHint(buffer, true);
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}
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/*
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* HeapTupleSetHintBits --- exported version of SetHintBits()
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*
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* This must be separate because of C99's brain-dead notions about how to
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* implement inline functions.
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*/
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void
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HeapTupleSetHintBits(HeapTupleHeader tuple, Buffer buffer,
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uint16 infomask, TransactionId xid)
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{
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SetHintBits(tuple, buffer, infomask, xid);
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}
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/*
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* HeapTupleSatisfiesSelf
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* True iff heap tuple is valid "for itself".
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*
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* Here, we consider the effects of:
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* all committed transactions (as of the current instant)
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* previous commands of this transaction
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* changes made by the current command
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*
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* Note:
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* Assumes heap tuple is valid.
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*
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* The satisfaction of "itself" requires the following:
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*
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* ((Xmin == my-transaction && the row was updated by the current transaction, and
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* (Xmax is null it was not deleted
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* [|| Xmax != my-transaction)]) [or it was deleted by another transaction]
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* ||
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*
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* (Xmin is committed && the row was modified by a committed transaction, and
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* (Xmax is null || the row has not been deleted, or
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* (Xmax != my-transaction && the row was deleted by another transaction
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* Xmax is not committed))) that has not been committed
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*/
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bool
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HeapTupleSatisfiesSelf(HeapTuple htup, Snapshot snapshot, Buffer buffer)
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{
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HeapTupleHeader tuple = htup->t_data;
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Assert(ItemPointerIsValid(&htup->t_self));
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Assert(htup->t_tableOid != InvalidOid);
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if (!HeapTupleHeaderXminCommitted(tuple))
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{
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if (HeapTupleHeaderXminInvalid(tuple))
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return false;
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/* Used by pre-9.0 binary upgrades */
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if (tuple->t_infomask & HEAP_MOVED_OFF)
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{
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TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
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if (TransactionIdIsCurrentTransactionId(xvac))
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return false;
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if (!TransactionIdIsInProgress(xvac))
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{
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if (TransactionIdDidCommit(xvac))
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{
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SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
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InvalidTransactionId);
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return false;
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}
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SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
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InvalidTransactionId);
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}
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}
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/* Used by pre-9.0 binary upgrades */
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else if (tuple->t_infomask & HEAP_MOVED_IN)
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{
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TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
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if (!TransactionIdIsCurrentTransactionId(xvac))
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{
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if (TransactionIdIsInProgress(xvac))
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return false;
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if (TransactionIdDidCommit(xvac))
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SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
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InvalidTransactionId);
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else
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{
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SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
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InvalidTransactionId);
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return false;
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}
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}
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}
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else if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmin(tuple)))
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{
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if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid */
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return true;
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if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask)) /* not deleter */
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return true;
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if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
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{
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TransactionId xmax;
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xmax = HeapTupleGetUpdateXid(tuple);
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/* not LOCKED_ONLY, so it has to have an xmax */
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Assert(TransactionIdIsValid(xmax));
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/* updating subtransaction must have aborted */
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if (!TransactionIdIsCurrentTransactionId(xmax))
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return true;
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else
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return false;
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}
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if (!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
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{
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/* deleting subtransaction must have aborted */
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SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
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InvalidTransactionId);
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return true;
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}
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return false;
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}
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else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
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return false;
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else if (TransactionIdDidCommit(HeapTupleHeaderGetRawXmin(tuple)))
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SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
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HeapTupleHeaderGetRawXmin(tuple));
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else
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{
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/* it must have aborted or crashed */
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SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
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InvalidTransactionId);
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return false;
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}
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}
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/* by here, the inserting transaction has committed */
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if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid or aborted */
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return true;
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if (tuple->t_infomask & HEAP_XMAX_COMMITTED)
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{
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if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
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return true;
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return false; /* updated by other */
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}
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if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
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{
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TransactionId xmax;
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if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
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return true;
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xmax = HeapTupleGetUpdateXid(tuple);
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/* not LOCKED_ONLY, so it has to have an xmax */
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Assert(TransactionIdIsValid(xmax));
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if (TransactionIdIsCurrentTransactionId(xmax))
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return false;
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if (TransactionIdIsInProgress(xmax))
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return true;
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if (TransactionIdDidCommit(xmax))
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return false;
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/* it must have aborted or crashed */
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return true;
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}
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if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetRawXmax(tuple)))
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{
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if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
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return true;
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return false;
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}
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if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmax(tuple)))
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return true;
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if (!TransactionIdDidCommit(HeapTupleHeaderGetRawXmax(tuple)))
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{
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/* it must have aborted or crashed */
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SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
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InvalidTransactionId);
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return true;
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}
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/* xmax transaction committed */
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if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
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{
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SetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
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InvalidTransactionId);
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return true;
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}
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SetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
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HeapTupleHeaderGetRawXmax(tuple));
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return false;
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}
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/*
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* HeapTupleSatisfiesAny
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* Dummy "satisfies" routine: any tuple satisfies SnapshotAny.
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*/
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bool
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HeapTupleSatisfiesAny(HeapTuple htup, Snapshot snapshot, Buffer buffer)
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{
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return true;
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}
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/*
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* HeapTupleSatisfiesToast
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* True iff heap tuple is valid as a TOAST row.
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*
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* This is a simplified version that only checks for VACUUM moving conditions.
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* It's appropriate for TOAST usage because TOAST really doesn't want to do
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* its own time qual checks; if you can see the main table row that contains
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* a TOAST reference, you should be able to see the TOASTed value. However,
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* vacuuming a TOAST table is independent of the main table, and in case such
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* a vacuum fails partway through, we'd better do this much checking.
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*
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* Among other things, this means you can't do UPDATEs of rows in a TOAST
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* table.
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*/
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bool
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HeapTupleSatisfiesToast(HeapTuple htup, Snapshot snapshot,
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Buffer buffer)
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{
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HeapTupleHeader tuple = htup->t_data;
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Assert(ItemPointerIsValid(&htup->t_self));
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Assert(htup->t_tableOid != InvalidOid);
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if (!HeapTupleHeaderXminCommitted(tuple))
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{
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if (HeapTupleHeaderXminInvalid(tuple))
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return false;
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/* Used by pre-9.0 binary upgrades */
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if (tuple->t_infomask & HEAP_MOVED_OFF)
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{
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TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
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if (TransactionIdIsCurrentTransactionId(xvac))
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return false;
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if (!TransactionIdIsInProgress(xvac))
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{
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if (TransactionIdDidCommit(xvac))
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{
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SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
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InvalidTransactionId);
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return false;
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}
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SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
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InvalidTransactionId);
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}
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}
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/* Used by pre-9.0 binary upgrades */
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else if (tuple->t_infomask & HEAP_MOVED_IN)
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{
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TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
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if (!TransactionIdIsCurrentTransactionId(xvac))
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{
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if (TransactionIdIsInProgress(xvac))
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return false;
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if (TransactionIdDidCommit(xvac))
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SetHintBits(tuple, buffer, HEAP_XMIN_COMMITTED,
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InvalidTransactionId);
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else
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{
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SetHintBits(tuple, buffer, HEAP_XMIN_INVALID,
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InvalidTransactionId);
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return false;
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}
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}
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}
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/*
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* An invalid Xmin can be left behind by a speculative insertion that
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* is canceled by super-deleting the tuple. This also applies to
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* TOAST tuples created during speculative insertion.
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*/
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else if (!TransactionIdIsValid(HeapTupleHeaderGetXmin(tuple)))
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return false;
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}
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/* otherwise assume the tuple is valid for TOAST. */
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return true;
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}
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/*
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* HeapTupleSatisfiesUpdate
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*
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* This function returns a more detailed result code than most of the
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* functions in this file, since UPDATE needs to know more than "is it
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* visible?". It also allows for user-supplied CommandId rather than
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* relying on CurrentCommandId.
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*
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* The possible return codes are:
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*
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* HeapTupleInvisible: the tuple didn't exist at all when the scan started,
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* e.g. it was created by a later CommandId.
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*
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* HeapTupleMayBeUpdated: The tuple is valid and visible, so it may be
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* updated.
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*
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* HeapTupleSelfUpdated: The tuple was updated by the current transaction,
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* after the current scan started.
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*
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* HeapTupleUpdated: The tuple was updated by a committed transaction.
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*
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* HeapTupleBeingUpdated: The tuple is being updated by an in-progress
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* transaction other than the current transaction. (Note: this includes
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* the case where the tuple is share-locked by a MultiXact, even if the
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* MultiXact includes the current transaction. Callers that want to
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* distinguish that case must test for it themselves.)
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*/
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HTSU_Result
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HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
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Buffer buffer)
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{
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HeapTupleHeader tuple = htup->t_data;
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|
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Assert(ItemPointerIsValid(&htup->t_self));
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Assert(htup->t_tableOid != InvalidOid);
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|
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if (!HeapTupleHeaderXminCommitted(tuple))
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{
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if (HeapTupleHeaderXminInvalid(tuple))
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return HeapTupleInvisible;
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|
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/* Used by pre-9.0 binary upgrades */
|
|
if (tuple->t_infomask & HEAP_MOVED_OFF)
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{
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TransactionId xvac = HeapTupleHeaderGetXvac(tuple);
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if (TransactionIdIsCurrentTransactionId(xvac))
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return HeapTupleInvisible;
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if (!TransactionIdIsInProgress(xvac))
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{
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if (TransactionIdDidCommit(xvac))
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{
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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 (MultiXactIdIsRunning(xmax, true))
|
|
return HeapTupleBeingUpdated;
|
|
else
|
|
return HeapTupleMayBeUpdated;
|
|
}
|
|
|
|
/*
|
|
* If the locker is gone, then there is nothing of interest
|
|
* left in this Xmax; otherwise, report the tuple as
|
|
* locked/updated.
|
|
*/
|
|
if (!TransactionIdIsInProgress(xmax))
|
|
return HeapTupleMayBeUpdated;
|
|
return HeapTupleBeingUpdated;
|
|
}
|
|
|
|
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));
|
|
|
|
/* deleting subtransaction must have aborted */
|
|
if (!TransactionIdIsCurrentTransactionId(xmax))
|
|
{
|
|
if (MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple),
|
|
false))
|
|
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_LOCKED_UPGRADED(tuple->t_infomask))
|
|
return HeapTupleMayBeUpdated;
|
|
|
|
if (HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask))
|
|
{
|
|
if (MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple), true))
|
|
return HeapTupleBeingUpdated;
|
|
|
|
SetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId);
|
|
return HeapTupleMayBeUpdated;
|
|
}
|
|
|
|
xmax = HeapTupleGetUpdateXid(tuple);
|
|
if (!TransactionIdIsValid(xmax))
|
|
{
|
|
if (MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple), false))
|
|
return HeapTupleBeingUpdated;
|
|
}
|
|
|
|
/* 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 (MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple), false))
|
|
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), false))
|
|
{
|
|
/*
|
|
* 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 HeapTupleBeingUpdated;
|
|
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 */
|
|
}
|
|
|
|
/*
|
|
* 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. If the tuple was
|
|
* inserted speculatively, meaning that the inserter might still back down
|
|
* on the insertion without aborting the whole transaction, the associated
|
|
* token is also returned in snapshot->speculativeToken.
|
|
*/
|
|
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;
|
|
snapshot->speculativeToken = 0;
|
|
|
|
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)))
|
|
{
|
|
/*
|
|
* Return the speculative token to caller. Caller can worry about
|
|
* xmax, since it requires a conclusively locked row version, and
|
|
* a concurrent update to this tuple is a conflict of its
|
|
* purposes.
|
|
*/
|
|
if (HeapTupleHeaderIsSpeculative(tuple))
|
|
{
|
|
snapshot->speculativeToken =
|
|
HeapTupleHeaderGetSpeculativeToken(tuple);
|
|
|
|
Assert(snapshot->speculativeToken != 0);
|
|
}
|
|
|
|
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 */
|
|
}
|
|
|
|
/*
|
|
* 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 that here, we will not update the tuple status hint bits if the
|
|
* inserting/deleting transaction is still running according to our snapshot,
|
|
* even if in reality it's committed or aborted by now. This is intentional.
|
|
* Checking the true transaction state would require access to high-traffic
|
|
* shared data structures, creating contention we'd rather do without, and it
|
|
* would not change the result of our visibility check anyway. The hint bits
|
|
* will be updated by the first visitor that has a snapshot new enough to see
|
|
* the inserting/deleting transaction as done. In the meantime, the cost of
|
|
* leaving the hint bits unset is basically that each HeapTupleSatisfiesMVCC
|
|
* call will need to run TransactionIdIsCurrentTransactionId in addition to
|
|
* XidInMVCCSnapshot (but it would have to do the latter anyway). In the old
|
|
* coding where we tried to set the hint bits as soon as possible, we instead
|
|
* did TransactionIdIsInProgress in each call --- to no avail, as long as the
|
|
* inserting/deleting transaction was still running --- which was more cycles
|
|
* and more contention on the PGXACT array.
|
|
*/
|
|
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 (!XidInMVCCSnapshot(xvac, snapshot))
|
|
{
|
|
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 (XidInMVCCSnapshot(xvac, snapshot))
|
|
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 (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmin(tuple), snapshot))
|
|
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;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* xmin is committed, but maybe not according to our snapshot */
|
|
if (!HeapTupleHeaderXminFrozen(tuple) &&
|
|
XidInMVCCSnapshot(HeapTupleHeaderGetRawXmin(tuple), snapshot))
|
|
return false; /* treat as still in progress */
|
|
}
|
|
|
|
/* by here, the inserting transaction has committed */
|
|
|
|
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 (XidInMVCCSnapshot(xmax, snapshot))
|
|
return true;
|
|
if (TransactionIdDidCommit(xmax))
|
|
return false; /* updating transaction committed */
|
|
/* 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 (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmax(tuple), snapshot))
|
|
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));
|
|
}
|
|
else
|
|
{
|
|
/* xmax is committed, but maybe not according to our snapshot */
|
|
if (XidInMVCCSnapshot(HeapTupleHeaderGetRawXmax(tuple), snapshot))
|
|
return true; /* treat as still in progress */
|
|
}
|
|
|
|
/* xmax transaction committed */
|
|
|
|
return false;
|
|
}
|
|
|
|
|
|
/*
|
|
* 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 (TransactionIdIsCurrentTransactionId(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 */
|
|
if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetUpdateXid(tuple)))
|
|
return HEAPTUPLE_DELETE_IN_PROGRESS;
|
|
/* deleting subtransaction must have aborted */
|
|
return HEAPTUPLE_INSERT_IN_PROGRESS;
|
|
}
|
|
else if (TransactionIdIsInProgress(HeapTupleHeaderGetRawXmin(tuple)))
|
|
{
|
|
/*
|
|
* It'd be possible to discern between INSERT/DELETE in progress
|
|
* here by looking at xmax - but that doesn't seem beneficial for
|
|
* the majority of callers and even detrimental for some. We'd
|
|
* rather have callers look at/wait for xmin than xmax. It's
|
|
* always correct to return INSERT_IN_PROGRESS because that's
|
|
* what's happening from the view of other backends.
|
|
*/
|
|
return HEAPTUPLE_INSERT_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.
|
|
*/
|
|
if (!(tuple->t_infomask & HEAP_XMAX_COMMITTED))
|
|
{
|
|
if (tuple->t_infomask & HEAP_XMAX_IS_MULTI)
|
|
{
|
|
/*
|
|
* If it's a pre-pg_upgrade tuple, the multixact cannot
|
|
* possibly be running; otherwise have to check.
|
|
*/
|
|
if (!HEAP_LOCKED_UPGRADED(tuple->t_infomask) &&
|
|
MultiXactIdIsRunning(HeapTupleHeaderGetRawXmax(tuple),
|
|
true))
|
|
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), false))
|
|
{
|
|
/* 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;
|
|
}
|
|
|
|
|
|
/*
|
|
* HeapTupleSatisfiesNonVacuumable
|
|
*
|
|
* True if tuple might be visible to some transaction; false if it's
|
|
* surely dead to everyone, ie, vacuumable.
|
|
*
|
|
* This is an interface to HeapTupleSatisfiesVacuum that meets the
|
|
* SnapshotSatisfiesFunc API, so it can be used through a Snapshot.
|
|
* snapshot->xmin must have been set up with the xmin horizon to use.
|
|
*/
|
|
bool
|
|
HeapTupleSatisfiesNonVacuumable(HeapTuple htup, Snapshot snapshot,
|
|
Buffer buffer)
|
|
{
|
|
return HeapTupleSatisfiesVacuum(htup, snapshot->xmin, buffer)
|
|
!= HEAPTUPLE_DEAD;
|
|
}
|
|
|
|
|
|
/*
|
|
* HeapTupleIsSurelyDead
|
|
*
|
|
* Cheaply determine whether a tuple is surely dead to all onlookers.
|
|
* We sometimes use this in lieu of HeapTupleSatisfiesVacuum when the
|
|
* tuple has just been tested by another visibility routine (usually
|
|
* HeapTupleSatisfiesMVCC) and, therefore, any hint bits that can be set
|
|
* should already be set. We assume that if no hint bits are set, the xmin
|
|
* or xmax transaction is still running. This is therefore faster than
|
|
* HeapTupleSatisfiesVacuum, because we don't consult PGXACT nor CLOG.
|
|
* It's okay to return FALSE when in doubt, but we must return TRUE only
|
|
* if the tuple is removable.
|
|
*/
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* XidInMVCCSnapshot
|
|
* Is the given XID still-in-progress according to the snapshot?
|
|
*
|
|
* Note: GetSnapshotData never stores either top xid or subxids of our own
|
|
* backend into a snapshot, so these xids will not be reported as "running"
|
|
* by this function. This is OK for current uses, because we always check
|
|
* TransactionIdIsCurrentTransactionId first, except when it's known the
|
|
* XID could not be ours anyway.
|
|
*/
|
|
bool
|
|
XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
|
|
{
|
|
uint32 i;
|
|
|
|
/*
|
|
* Make a quick range check to eliminate most XIDs without looking at the
|
|
* xip arrays. Note that this is OK even if we convert a subxact XID to
|
|
* its parent below, because a subxact with XID < xmin has surely also got
|
|
* a parent with XID < xmin, while one with XID >= xmax must belong to a
|
|
* parent that was not yet committed at the time of this snapshot.
|
|
*/
|
|
|
|
/* Any xid < xmin is not in-progress */
|
|
if (TransactionIdPrecedes(xid, snapshot->xmin))
|
|
return false;
|
|
/* Any xid >= xmax is in-progress */
|
|
if (TransactionIdFollowsOrEquals(xid, snapshot->xmax))
|
|
return true;
|
|
|
|
/*
|
|
* Snapshot information is stored slightly differently in snapshots taken
|
|
* during recovery.
|
|
*/
|
|
if (!snapshot->takenDuringRecovery)
|
|
{
|
|
/*
|
|
* If the snapshot contains full subxact data, the fastest way to
|
|
* check things is just to compare the given XID against both subxact
|
|
* XIDs and top-level XIDs. If the snapshot overflowed, we have to
|
|
* use pg_subtrans to convert a subxact XID to its parent XID, but
|
|
* then we need only look at top-level XIDs not subxacts.
|
|
*/
|
|
if (!snapshot->suboverflowed)
|
|
{
|
|
/* we have full data, so search subxip */
|
|
int32 j;
|
|
|
|
for (j = 0; j < snapshot->subxcnt; j++)
|
|
{
|
|
if (TransactionIdEquals(xid, snapshot->subxip[j]))
|
|
return true;
|
|
}
|
|
|
|
/* not there, fall through to search xip[] */
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* Snapshot overflowed, so convert xid to top-level. This is safe
|
|
* because we eliminated too-old XIDs above.
|
|
*/
|
|
xid = SubTransGetTopmostTransaction(xid);
|
|
|
|
/*
|
|
* If xid was indeed a subxact, we might now have an xid < xmin,
|
|
* so recheck to avoid an array scan. No point in rechecking
|
|
* xmax.
|
|
*/
|
|
if (TransactionIdPrecedes(xid, snapshot->xmin))
|
|
return false;
|
|
}
|
|
|
|
for (i = 0; i < snapshot->xcnt; i++)
|
|
{
|
|
if (TransactionIdEquals(xid, snapshot->xip[i]))
|
|
return true;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
int32 j;
|
|
|
|
/*
|
|
* In recovery we store all xids in the subxact array because it is by
|
|
* far the bigger array, and we mostly don't know which xids are
|
|
* top-level and which are subxacts. The xip array is empty.
|
|
*
|
|
* We start by searching subtrans, if we overflowed.
|
|
*/
|
|
if (snapshot->suboverflowed)
|
|
{
|
|
/*
|
|
* Snapshot overflowed, so convert xid to top-level. This is safe
|
|
* because we eliminated too-old XIDs above.
|
|
*/
|
|
xid = SubTransGetTopmostTransaction(xid);
|
|
|
|
/*
|
|
* If xid was indeed a subxact, we might now have an xid < xmin,
|
|
* so recheck to avoid an array scan. No point in rechecking
|
|
* xmax.
|
|
*/
|
|
if (TransactionIdPrecedes(xid, snapshot->xmin))
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* We now have either a top-level xid higher than xmin or an
|
|
* indeterminate xid. We don't know whether it's top level or subxact
|
|
* but it doesn't matter. If it's present, the xid is visible.
|
|
*/
|
|
for (j = 0; j < snapshot->subxcnt; j++)
|
|
{
|
|
if (TransactionIdEquals(xid, snapshot->subxip[j]))
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Is the tuple really only locked? That is, is it not updated?
|
|
*
|
|
* It's easy to check just infomask bits if the locker is not a multi; but
|
|
* otherwise we need to verify that the updating transaction has not aborted.
|
|
*
|
|
* This function is here because it follows the same time qualification rules
|
|
* laid out at the top of this file.
|
|
*/
|
|
bool
|
|
HeapTupleHeaderIsOnlyLocked(HeapTupleHeader tuple)
|
|
{
|
|
TransactionId xmax;
|
|
|
|
/* if there's no valid Xmax, then there's obviously no update either */
|
|
if (tuple->t_infomask & HEAP_XMAX_INVALID)
|
|
return true;
|
|
|
|
if (tuple->t_infomask & HEAP_XMAX_LOCK_ONLY)
|
|
return true;
|
|
|
|
/* invalid xmax means no update */
|
|
if (!TransactionIdIsValid(HeapTupleHeaderGetRawXmax(tuple)))
|
|
return true;
|
|
|
|
/*
|
|
* if HEAP_XMAX_LOCK_ONLY is not set and not a multi, then this must
|
|
* necessarily have been updated
|
|
*/
|
|
if (!(tuple->t_infomask & HEAP_XMAX_IS_MULTI))
|
|
return false;
|
|
|
|
/* ... but if it's a multi, then perhaps the updating Xid aborted. */
|
|
xmax = HeapTupleGetUpdateXid(tuple);
|
|
|
|
/* not LOCKED_ONLY, so it has to have an xmax */
|
|
Assert(TransactionIdIsValid(xmax));
|
|
|
|
if (TransactionIdIsCurrentTransactionId(xmax))
|
|
return false;
|
|
if (TransactionIdIsInProgress(xmax))
|
|
return false;
|
|
if (TransactionIdDidCommit(xmax))
|
|
return false;
|
|
|
|
/*
|
|
* not current, not in progress, not committed -- must have aborted or
|
|
* crashed
|
|
*/
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* check whether the transaction id 'xid' is in the pre-sorted array 'xip'.
|
|
*/
|
|
static bool
|
|
TransactionIdInArray(TransactionId xid, TransactionId *xip, Size num)
|
|
{
|
|
return bsearch(&xid, xip, num,
|
|
sizeof(TransactionId), xidComparator) != NULL;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|