procarray.h File Reference

#include "storage/lock.h"
#include "storage/standby.h"
#include "utils/relcache.h"
#include "utils/snapshot.h"

Include dependency graph for procarray.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Functions
Size	ProcArrayShmemSize (void)
void	ProcArrayShmemInit (void)
void	ProcArrayAdd (PGPROC *proc)
void	ProcArrayRemove (PGPROC *proc, TransactionId latestXid)
void	ProcArrayEndTransaction (PGPROC *proc, TransactionId latestXid)
void	ProcArrayClearTransaction (PGPROC *proc)
void	ProcArrayInitRecovery (TransactionId initializedUptoXID)
void	ProcArrayApplyRecoveryInfo (RunningTransactions running)
void	ProcArrayApplyXidAssignment (TransactionId topxid, int nsubxids, TransactionId *subxids)
void	RecordKnownAssignedTransactionIds (TransactionId xid)
void	ExpireTreeKnownAssignedTransactionIds (TransactionId xid, int nsubxids, TransactionId *subxids, TransactionId max_xid)
void	ExpireAllKnownAssignedTransactionIds (void)
void	ExpireOldKnownAssignedTransactionIds (TransactionId xid)
void	KnownAssignedTransactionIdsIdleMaintenance (void)
int	GetMaxSnapshotXidCount (void)
int	GetMaxSnapshotSubxidCount (void)
Snapshot	GetSnapshotData (Snapshot snapshot)
bool	ProcArrayInstallImportedXmin (TransactionId xmin, VirtualTransactionId *sourcevxid)
bool	ProcArrayInstallRestoredXmin (TransactionId xmin, PGPROC *proc)
RunningTransactions	GetRunningTransactionData (void)
bool	TransactionIdIsInProgress (TransactionId xid)
TransactionId	GetOldestNonRemovableTransactionId (Relation rel)
TransactionId	GetOldestTransactionIdConsideredRunning (void)
TransactionId	GetOldestActiveTransactionId (bool inCommitOnly, bool allDbs)
TransactionId	GetOldestSafeDecodingTransactionId (bool catalogOnly)
void	GetReplicationHorizons (TransactionId *xmin, TransactionId *catalog_xmin)
VirtualTransactionId *	GetVirtualXIDsDelayingChkpt (int *nvxids, int type)
bool	HaveVirtualXIDsDelayingChkpt (VirtualTransactionId *vxids, int nvxids, int type)
PGPROC *	ProcNumberGetProc (int procNumber)
void	ProcNumberGetTransactionIds (int procNumber, TransactionId *xid, TransactionId *xmin, int *nsubxid, bool *overflowed)
PGPROC *	BackendPidGetProc (int pid)
PGPROC *	BackendPidGetProcWithLock (int pid)
int	BackendXidGetPid (TransactionId xid)
bool	IsBackendPid (int pid)
VirtualTransactionId *	GetCurrentVirtualXIDs (TransactionId limitXmin, bool excludeXmin0, bool allDbs, int excludeVacuum, int *nvxids)
VirtualTransactionId *	GetConflictingVirtualXIDs (TransactionId limitXmin, Oid dbOid)
bool	SignalRecoveryConflict (PGPROC *proc, pid_t pid, RecoveryConflictReason reason)
bool	SignalRecoveryConflictWithVirtualXID (VirtualTransactionId vxid, RecoveryConflictReason reason)
void	SignalRecoveryConflictWithDatabase (Oid databaseid, RecoveryConflictReason reason)
bool	MinimumActiveBackends (int min)
int	CountDBBackends (Oid databaseid)
int	CountDBConnections (Oid databaseid)
int	CountUserBackends (Oid roleid)
bool	CountOtherDBBackends (Oid databaseId, int *nbackends, int *nprepared)
void	TerminateOtherDBBackends (Oid databaseId)
void	XidCacheRemoveRunningXids (TransactionId xid, int nxids, const TransactionId *xids, TransactionId latestXid)
void	ProcArraySetReplicationSlotXmin (TransactionId xmin, TransactionId catalog_xmin, bool already_locked)
void	ProcArrayGetReplicationSlotXmin (TransactionId *xmin, TransactionId *catalog_xmin)

Function Documentation

BackendPidGetProc()

PGPROC * BackendPidGetProc ( int  pid )

extern

Definition at line 3156 of file procarray.c.

{
    PGPROC     *result;
 
    if (pid == 0)               /* never match dummy PGPROCs */
        return NULL;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    result = BackendPidGetProcWithLock(pid);
 
    LWLockRelease(ProcArrayLock);
 
    return result;
}

References BackendPidGetProcWithLock(), LW_SHARED, LWLockAcquire(), and LWLockRelease().

Referenced by IsBackendPid(), pg_isolation_test_session_is_blocked(), pg_log_backend_memory_contexts(), pg_signal_backend(), pg_stat_get_activity(), pg_stat_get_backend_wait_event(), pg_stat_get_backend_wait_event_type(), pg_stat_reset_backend_stats(), pgstat_fetch_stat_backend_by_pid(), TerminateBackgroundWorkersForDatabase(), TerminateOtherDBBackends(), and test_shm_mq_main().

BackendPidGetProcWithLock()

PGPROC * BackendPidGetProcWithLock ( int  pid )

extern

Definition at line 3179 of file procarray.c.

{
    PGPROC     *result = NULL;
    ProcArrayStruct *arrayP = procArray;
    int         index;
 
    if (pid == 0)               /* never match dummy PGPROCs */
        return NULL;
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        PGPROC     *proc = &allProcs[arrayP->pgprocnos[index]];
 
        if (proc->pid == pid)
        {
            result = proc;
            break;
        }
    }
 
    return result;
}

References allProcs, ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PGPROC::pid, and procArray.

Referenced by BackendPidGetProc(), and GetBlockerStatusData().

BackendXidGetPid()

int BackendXidGetPid ( TransactionId  xid )

extern

Definition at line 3216 of file procarray.c.

{
    int         result = 0;
    ProcArrayStruct *arrayP = procArray;
    TransactionId *other_xids = ProcGlobal->xids;
    int         index;
 
    if (xid == InvalidTransactionId)    /* never match invalid xid */
        return 0;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        if (other_xids[index] == xid)
        {
            int         pgprocno = arrayP->pgprocnos[index];
            PGPROC     *proc = &allProcs[pgprocno];
 
            result = proc->pid;
            break;
        }
    }
 
    LWLockRelease(ProcArrayLock);
 
    return result;
}

References allProcs, InvalidTransactionId, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, ProcGlobal, and PROC_HDR::xids.

Referenced by pgrowlocks().

CountDBBackends()

int CountDBBackends ( Oid  databaseid )

extern

Definition at line 3629 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        if (proc->pid == 0)
            continue;           /* do not count prepared xacts */
        if (!OidIsValid(databaseid) ||
            proc->databaseId == databaseid)
            count++;
    }
 
    LWLockRelease(ProcArrayLock);
 
    return count;
}

References allProcs, PGPROC::databaseId, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, OidIsValid, ProcArrayStruct::pgprocnos, PGPROC::pid, and procArray.

Referenced by ResolveRecoveryConflictWithDatabase().

CountDBConnections()

int CountDBConnections ( Oid  databaseid )

extern

Definition at line 3658 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        if (proc->pid == 0)
            continue;           /* do not count prepared xacts */
        if (proc->backendType != B_BACKEND)
            continue;           /* count only regular backend processes */
        if (!OidIsValid(databaseid) ||
            proc->databaseId == databaseid)
            count++;
    }
 
    LWLockRelease(ProcArrayLock);
 
    return count;
}

References allProcs, B_BACKEND, PGPROC::backendType, PGPROC::databaseId, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, OidIsValid, ProcArrayStruct::pgprocnos, PGPROC::pid, and procArray.

Referenced by CheckMyDatabase().

CountOtherDBBackends()

bool CountOtherDBBackends ( Oid  databaseId, int *  nbackends, int *  nprepared  )

extern

Definition at line 3742 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
 
#define MAXAUTOVACPIDS  10      /* max autovacs to SIGTERM per iteration */
    int         autovac_pids[MAXAUTOVACPIDS];
 
    /*
     * Retry up to 50 times with 100ms between attempts (max 5s total). Can be
     * reduced to 3 attempts (max 0.3s total) to speed up tests.
     */
    int         ntries = 50;
 
#ifdef USE_INJECTION_POINTS
    if (IS_INJECTION_POINT_ATTACHED("procarray-reduce-count"))
        ntries = 3;
#endif
 
    for (int tries = 0; tries < ntries; tries++)
    {
        int         nautovacs = 0;
        bool        found = false;
        int         index;
 
        CHECK_FOR_INTERRUPTS();
 
        *nbackends = *nprepared = 0;
 
        LWLockAcquire(ProcArrayLock, LW_SHARED);
 
        for (index = 0; index < arrayP->numProcs; index++)
        {
            int         pgprocno = arrayP->pgprocnos[index];
            PGPROC     *proc = &allProcs[pgprocno];
            uint8       statusFlags = ProcGlobal->statusFlags[index];
 
            if (proc->databaseId != databaseId)
                continue;
            if (proc == MyProc)
                continue;
 
            found = true;
 
            if (proc->pid == 0)
                (*nprepared)++;
            else
            {
                (*nbackends)++;
                if ((statusFlags & PROC_IS_AUTOVACUUM) &&
                    nautovacs < MAXAUTOVACPIDS)
                    autovac_pids[nautovacs++] = proc->pid;
            }
        }
 
        LWLockRelease(ProcArrayLock);
 
        if (!found)
            return false;       /* no conflicting backends, so done */
 
        /*
         * Send SIGTERM to any conflicting autovacuums before sleeping. We
         * postpone this step until after the loop because we don't want to
         * hold ProcArrayLock while issuing kill(). We have no idea what might
         * block kill() inside the kernel...
         */
        for (index = 0; index < nautovacs; index++)
            (void) kill(autovac_pids[index], SIGTERM);  /* ignore any error */
 
        /*
         * Terminate all background workers for this database, if they have
         * requested it (BGWORKER_INTERRUPTIBLE).
         */
        TerminateBackgroundWorkersForDatabase(databaseId);
 
        /* sleep, then try again */
        pg_usleep(100 * 1000L); /* 100ms */
    }
 
    return true;                /* timed out, still conflicts */
}

References allProcs, CHECK_FOR_INTERRUPTS, PGPROC::databaseId, IS_INJECTION_POINT_ATTACHED, kill, LW_SHARED, LWLockAcquire(), LWLockRelease(), MAXAUTOVACPIDS, MyProc, ProcArrayStruct::numProcs, pg_usleep(), ProcArrayStruct::pgprocnos, PGPROC::pid, PROC_IS_AUTOVACUUM, procArray, ProcGlobal, PROC_HDR::statusFlags, and TerminateBackgroundWorkersForDatabase().

Referenced by createdb(), dropdb(), movedb(), and RenameDatabase().

CountUserBackends()

int CountUserBackends ( Oid  roleid )

extern

Definition at line 3690 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        if (proc->pid == 0)
            continue;           /* do not count prepared xacts */
        if (proc->backendType != B_BACKEND)
            continue;           /* count only regular backend processes */
        if (proc->roleId == roleid)
            count++;
    }
 
    LWLockRelease(ProcArrayLock);
 
    return count;
}

References allProcs, B_BACKEND, PGPROC::backendType, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, and PGPROC::roleId.

Referenced by InitializeSessionUserId().

ExpireAllKnownAssignedTransactionIds()

void ExpireAllKnownAssignedTransactionIds ( void  )

extern

Definition at line 4505 of file procarray.c.

{
    FullTransactionId latestXid;
 
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
    KnownAssignedXidsRemovePreceding(InvalidTransactionId);
 
    /* Reset latestCompletedXid to nextXid - 1 */
    Assert(FullTransactionIdIsValid(TransamVariables->nextXid));
    latestXid = TransamVariables->nextXid;
    FullTransactionIdRetreat(&latestXid);
    TransamVariables->latestCompletedXid = latestXid;
 
    /*
     * Any transactions that were in-progress were effectively aborted, so
     * advance xactCompletionCount.
     */
    TransamVariables->xactCompletionCount++;
 
    /*
     * Reset lastOverflowedXid.  Currently, lastOverflowedXid has no use after
     * the call of this function.  But do this for unification with what
     * ExpireOldKnownAssignedTransactionIds() do.
     */
    procArray->lastOverflowedXid = InvalidTransactionId;
    LWLockRelease(ProcArrayLock);
}

References Assert, FullTransactionIdIsValid, FullTransactionIdRetreat(), InvalidTransactionId, KnownAssignedXidsRemovePreceding(), ProcArrayStruct::lastOverflowedXid, TransamVariablesData::latestCompletedXid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), TransamVariablesData::nextXid, procArray, TransamVariables, and TransamVariablesData::xactCompletionCount.

Referenced by ShutdownRecoveryTransactionEnvironment().

ExpireOldKnownAssignedTransactionIds()

void ExpireOldKnownAssignedTransactionIds ( TransactionId  xid )

extern

Definition at line 4539 of file procarray.c.

{
    TransactionId latestXid;
 
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    /* As in ProcArrayEndTransaction, advance latestCompletedXid */
    latestXid = xid;
    TransactionIdRetreat(latestXid);
    MaintainLatestCompletedXidRecovery(latestXid);
 
    /* ... and xactCompletionCount */
    TransamVariables->xactCompletionCount++;
 
    /*
     * Reset lastOverflowedXid if we know all transactions that have been
     * possibly running are being gone.  Not doing so could cause an incorrect
     * lastOverflowedXid value, which makes extra snapshots be marked as
     * suboverflowed.
     */
    if (TransactionIdPrecedes(procArray->lastOverflowedXid, xid))
        procArray->lastOverflowedXid = InvalidTransactionId;
    KnownAssignedXidsRemovePreceding(xid);
    LWLockRelease(ProcArrayLock);
}

References InvalidTransactionId, KnownAssignedXidsRemovePreceding(), ProcArrayStruct::lastOverflowedXid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaintainLatestCompletedXidRecovery(), procArray, TransactionIdPrecedes(), TransactionIdRetreat, TransamVariables, and TransamVariablesData::xactCompletionCount.

Referenced by ProcArrayApplyRecoveryInfo().

ExpireTreeKnownAssignedTransactionIds()

void ExpireTreeKnownAssignedTransactionIds ( TransactionId  xid, int  nsubxids, TransactionId *  subxids, TransactionId  max_xid  )

extern

Definition at line 4479 of file procarray.c.

{
    Assert(standbyState >= STANDBY_INITIALIZED);
 
    /*
     * Uses same locking as transaction commit
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    KnownAssignedXidsRemoveTree(xid, nsubxids, subxids);
 
    /* As in ProcArrayEndTransaction, advance latestCompletedXid */
    MaintainLatestCompletedXidRecovery(max_xid);
 
    /* ... and xactCompletionCount */
    TransamVariables->xactCompletionCount++;
 
    LWLockRelease(ProcArrayLock);
}

References Assert, KnownAssignedXidsRemoveTree(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaintainLatestCompletedXidRecovery(), STANDBY_INITIALIZED, standbyState, TransamVariables, and TransamVariablesData::xactCompletionCount.

Referenced by xact_redo_abort(), and xact_redo_commit().

GetConflictingVirtualXIDs()

VirtualTransactionId * GetConflictingVirtualXIDs ( TransactionId  limitXmin, Oid  dbOid  )

extern

Definition at line 3376 of file procarray.c.

{
    static VirtualTransactionId *vxids;
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    /*
     * If first time through, get workspace to remember main XIDs in. We
     * malloc it permanently to avoid repeated palloc/pfree overhead. Allow
     * result space, remembering room for a terminator.
     */
    if (vxids == NULL)
    {
        vxids = (VirtualTransactionId *)
            malloc(sizeof(VirtualTransactionId) * (arrayP->maxProcs + 1));
        if (vxids == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
    }
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        /* Exclude prepared transactions */
        if (proc->pid == 0)
            continue;
 
        if (!OidIsValid(dbOid) ||
            proc->databaseId == dbOid)
        {
            /* Fetch xmin just once - can't change on us, but good coding */
            TransactionId pxmin = UINT32_ACCESS_ONCE(proc->xmin);
 
            /*
             * We ignore an invalid pxmin because this means that backend has
             * no snapshot currently. We hold a Share lock to avoid contention
             * with users taking snapshots.  That is not a problem because the
             * current xmin is always at least one higher than the latest
             * removed xid, so any new snapshot would never conflict with the
             * test here.
             */
            if (!TransactionIdIsValid(limitXmin) ||
                (TransactionIdIsValid(pxmin) && !TransactionIdFollows(pxmin, limitXmin)))
            {
                VirtualTransactionId vxid;
 
                GET_VXID_FROM_PGPROC(vxid, *proc);
                if (VirtualTransactionIdIsValid(vxid))
                    vxids[count++] = vxid;
            }
        }
    }
 
    LWLockRelease(ProcArrayLock);
 
    /* add the terminator */
    vxids[count].procNumber = INVALID_PROC_NUMBER;
    vxids[count].localTransactionId = InvalidLocalTransactionId;
 
    return vxids;
}

References allProcs, PGPROC::databaseId, ereport, errcode(), errmsg, ERROR, GET_VXID_FROM_PGPROC, INVALID_PROC_NUMBER, InvalidLocalTransactionId, VirtualTransactionId::localTransactionId, LW_SHARED, LWLockAcquire(), LWLockRelease(), malloc, ProcArrayStruct::maxProcs, ProcArrayStruct::numProcs, OidIsValid, ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, VirtualTransactionId::procNumber, TransactionIdFollows(), TransactionIdIsValid, UINT32_ACCESS_ONCE, VirtualTransactionIdIsValid, and PGPROC::xmin.

Referenced by ResolveRecoveryConflictWithSnapshot(), and ResolveRecoveryConflictWithTablespace().

GetCurrentVirtualXIDs()

VirtualTransactionId * GetCurrentVirtualXIDs ( TransactionId  limitXmin, bool  excludeXmin0, bool  allDbs, int  excludeVacuum, int *  nvxids  )

extern

Definition at line 3284 of file procarray.c.

{
    VirtualTransactionId *vxids;
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    /* allocate what's certainly enough result space */
    vxids = palloc_array(VirtualTransactionId, arrayP->maxProcs);
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
        uint8       statusFlags = ProcGlobal->statusFlags[index];
 
        if (proc == MyProc)
            continue;
 
        if (excludeVacuum & statusFlags)
            continue;
 
        if (allDbs || proc->databaseId == MyDatabaseId)
        {
            /* Fetch xmin just once - might change on us */
            TransactionId pxmin = UINT32_ACCESS_ONCE(proc->xmin);
 
            if (excludeXmin0 && !TransactionIdIsValid(pxmin))
                continue;
 
            /*
             * InvalidTransactionId precedes all other XIDs, so a proc that
             * hasn't set xmin yet will not be rejected by this test.
             */
            if (!TransactionIdIsValid(limitXmin) ||
                TransactionIdPrecedesOrEquals(pxmin, limitXmin))
            {
                VirtualTransactionId vxid;
 
                GET_VXID_FROM_PGPROC(vxid, *proc);
                if (VirtualTransactionIdIsValid(vxid))
                    vxids[count++] = vxid;
            }
        }
    }
 
    LWLockRelease(ProcArrayLock);
 
    *nvxids = count;
    return vxids;
}

References allProcs, PGPROC::databaseId, GET_VXID_FROM_PGPROC, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::maxProcs, MyDatabaseId, MyProc, ProcArrayStruct::numProcs, palloc_array, ProcArrayStruct::pgprocnos, procArray, ProcGlobal, PROC_HDR::statusFlags, TransactionIdIsValid, TransactionIdPrecedesOrEquals(), UINT32_ACCESS_ONCE, VirtualTransactionIdIsValid, and PGPROC::xmin.

Referenced by WaitForOlderSnapshots().

GetMaxSnapshotSubxidCount()

int GetMaxSnapshotSubxidCount ( void  )

extern

Definition at line 2027 of file procarray.c.

{
    return TOTAL_MAX_CACHED_SUBXIDS;
}

References TOTAL_MAX_CACHED_SUBXIDS.

Referenced by ExportSnapshot(), GetSnapshotData(), ImportSnapshot(), and SetTransactionSnapshot().

GetMaxSnapshotXidCount()

int GetMaxSnapshotXidCount ( void  )

extern

Definition at line 2016 of file procarray.c.

{
    return procArray->maxProcs;
}

References ProcArrayStruct::maxProcs, and procArray.

Referenced by GetSnapshotData(), ImportSnapshot(), SetTransactionSnapshot(), and SnapBuildInitialSnapshot().

GetOldestActiveTransactionId()

TransactionId GetOldestActiveTransactionId ( bool  inCommitOnly, bool  allDbs  )

extern

Definition at line 2832 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    TransactionId *other_xids = ProcGlobal->xids;
    TransactionId oldestRunningXid;
    int         index;
 
    Assert(!RecoveryInProgress());
 
    /*
     * Read nextXid, as the upper bound of what's still active.
     *
     * Reading a TransactionId is atomic, but we must grab the lock to make
     * sure that all XIDs < nextXid are already present in the proc array (or
     * have already completed), when we spin over it.
     */
    LWLockAcquire(XidGenLock, LW_SHARED);
    oldestRunningXid = XidFromFullTransactionId(TransamVariables->nextXid);
    LWLockRelease(XidGenLock);
 
    /*
     * Spin over procArray collecting all xids and subxids.
     */
    LWLockAcquire(ProcArrayLock, LW_SHARED);
    for (index = 0; index < arrayP->numProcs; index++)
    {
        TransactionId xid;
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        /* Fetch xid just once - see GetNewTransactionId */
        xid = UINT32_ACCESS_ONCE(other_xids[index]);
 
        if (!TransactionIdIsNormal(xid))
            continue;
 
        if (inCommitOnly &&
            (proc->delayChkptFlags & DELAY_CHKPT_IN_COMMIT) == 0)
            continue;
 
        if (!allDbs && proc->databaseId != MyDatabaseId)
            continue;
 
        if (TransactionIdPrecedes(xid, oldestRunningXid))
            oldestRunningXid = xid;
 
        /*
         * Top-level XID of a transaction is always less than any of its
         * subxids, so we don't need to check if any of the subxids are
         * smaller than oldestRunningXid
         */
    }
    LWLockRelease(ProcArrayLock);
 
    return oldestRunningXid;
}

References allProcs, Assert, PGPROC::databaseId, DELAY_CHKPT_IN_COMMIT, PGPROC::delayChkptFlags, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyDatabaseId, TransamVariablesData::nextXid, ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, procArray, ProcGlobal, RecoveryInProgress(), TransactionIdIsNormal, TransactionIdPrecedes(), TransamVariables, UINT32_ACCESS_ONCE, XidFromFullTransactionId, and PROC_HDR::xids.

Referenced by CreateCheckPoint(), get_candidate_xid(), and ProcessStandbyPSRequestMessage().

GetOldestNonRemovableTransactionId()

TransactionId GetOldestNonRemovableTransactionId ( Relation  rel )

extern

Definition at line 1952 of file procarray.c.

{
    ComputeXidHorizonsResult horizons;
 
    ComputeXidHorizons(&horizons);
 
    switch (GlobalVisHorizonKindForRel(rel))
    {
        case VISHORIZON_SHARED:
            return horizons.shared_oldest_nonremovable;
        case VISHORIZON_CATALOG:
            return horizons.catalog_oldest_nonremovable;
        case VISHORIZON_DATA:
            return horizons.data_oldest_nonremovable;
        case VISHORIZON_TEMP:
            return horizons.temp_oldest_nonremovable;
    }
 
    /* just to prevent compiler warnings */
    return InvalidTransactionId;
}

References ComputeXidHorizonsResult::catalog_oldest_nonremovable, ComputeXidHorizons(), ComputeXidHorizonsResult::data_oldest_nonremovable, GlobalVisHorizonKindForRel(), InvalidTransactionId, ComputeXidHorizonsResult::shared_oldest_nonremovable, ComputeXidHorizonsResult::temp_oldest_nonremovable, VISHORIZON_CATALOG, VISHORIZON_DATA, VISHORIZON_SHARED, and VISHORIZON_TEMP.

Referenced by _bt_pendingfsm_finalize(), GetStrictOldestNonRemovableTransactionId(), heapam_index_build_range_scan(), removable_cutoff(), statapprox_heap(), vac_update_datfrozenxid(), and vacuum_get_cutoffs().

GetOldestSafeDecodingTransactionId()

TransactionId GetOldestSafeDecodingTransactionId ( bool  catalogOnly )

extern

Definition at line 2906 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    TransactionId oldestSafeXid;
    int         index;
    bool        recovery_in_progress = RecoveryInProgress();
 
    Assert(LWLockHeldByMe(ProcArrayLock));
 
    /*
     * Acquire XidGenLock, so no transactions can acquire an xid while we're
     * running. If no transaction with xid were running concurrently a new xid
     * could influence the RecentXmin et al.
     *
     * We initialize the computation to nextXid since that's guaranteed to be
     * a safe, albeit pessimal, value.
     */
    LWLockAcquire(XidGenLock, LW_SHARED);
    oldestSafeXid = XidFromFullTransactionId(TransamVariables->nextXid);
 
    /*
     * If there's already a slot pegging the xmin horizon, we can start with
     * that value, it's guaranteed to be safe since it's computed by this
     * routine initially and has been enforced since.  We can always use the
     * slot's general xmin horizon, but the catalog horizon is only usable
     * when only catalog data is going to be looked at.
     */
    if (TransactionIdIsValid(procArray->replication_slot_xmin) &&
        TransactionIdPrecedes(procArray->replication_slot_xmin,
                              oldestSafeXid))
        oldestSafeXid = procArray->replication_slot_xmin;
 
    if (catalogOnly &&
        TransactionIdIsValid(procArray->replication_slot_catalog_xmin) &&
        TransactionIdPrecedes(procArray->replication_slot_catalog_xmin,
                              oldestSafeXid))
        oldestSafeXid = procArray->replication_slot_catalog_xmin;
 
    /*
     * If we're not in recovery, we walk over the procarray and collect the
     * lowest xid. Since we're called with ProcArrayLock held and have
     * acquired XidGenLock, no entries can vanish concurrently, since
     * ProcGlobal->xids[i] is only set with XidGenLock held and only cleared
     * with ProcArrayLock held.
     *
     * In recovery we can't lower the safe value besides what we've computed
     * above, so we'll have to wait a bit longer there. We unfortunately can
     * *not* use KnownAssignedXidsGetOldestXmin() since the KnownAssignedXids
     * machinery can miss values and return an older value than is safe.
     */
    if (!recovery_in_progress)
    {
        TransactionId *other_xids = ProcGlobal->xids;
 
        /*
         * Spin over procArray collecting min(ProcGlobal->xids[i])
         */
        for (index = 0; index < arrayP->numProcs; index++)
        {
            TransactionId xid;
 
            /* Fetch xid just once - see GetNewTransactionId */
            xid = UINT32_ACCESS_ONCE(other_xids[index]);
 
            if (!TransactionIdIsNormal(xid))
                continue;
 
            if (TransactionIdPrecedes(xid, oldestSafeXid))
                oldestSafeXid = xid;
        }
    }
 
    LWLockRelease(XidGenLock);
 
    return oldestSafeXid;
}

References Assert, LW_SHARED, LWLockAcquire(), LWLockHeldByMe(), LWLockRelease(), TransamVariablesData::nextXid, ProcArrayStruct::numProcs, procArray, ProcGlobal, RecoveryInProgress(), ProcArrayStruct::replication_slot_catalog_xmin, ProcArrayStruct::replication_slot_xmin, TransactionIdIsNormal, TransactionIdIsValid, TransactionIdPrecedes(), TransamVariables, UINT32_ACCESS_ONCE, XidFromFullTransactionId, and PROC_HDR::xids.

Referenced by CreateInitDecodingContext(), init_conflict_slot_xmin(), SnapBuildInitialSnapshot(), and synchronize_one_slot().

GetOldestTransactionIdConsideredRunning()

TransactionId GetOldestTransactionIdConsideredRunning ( void  )

extern

Definition at line 1981 of file procarray.c.

{
    ComputeXidHorizonsResult horizons;
 
    ComputeXidHorizons(&horizons);
 
    return horizons.oldest_considered_running;
}

References ComputeXidHorizons(), and ComputeXidHorizonsResult::oldest_considered_running.

Referenced by CreateCheckPoint(), and CreateRestartPoint().

GetReplicationHorizons()

void GetReplicationHorizons ( TransactionId *  xmin, TransactionId *  catalog_xmin  )

extern

Definition at line 1994 of file procarray.c.

{
    ComputeXidHorizonsResult horizons;
 
    ComputeXidHorizons(&horizons);
 
    /*
     * Don't want to use shared_oldest_nonremovable here, as that contains the
     * effect of replication slot's catalog_xmin. We want to send a separate
     * feedback for the catalog horizon, so the primary can remove data table
     * contents more aggressively.
     */
    *xmin = horizons.shared_oldest_nonremovable_raw;
    *catalog_xmin = horizons.slot_catalog_xmin;
}

References ComputeXidHorizons(), ComputeXidHorizonsResult::shared_oldest_nonremovable_raw, and ComputeXidHorizonsResult::slot_catalog_xmin.

Referenced by XLogWalRcvSendHSFeedback().

GetRunningTransactionData()

RunningTransactions GetRunningTransactionData ( void  )

extern

Definition at line 2636 of file procarray.c.

{
    /* result workspace */
    static RunningTransactionsData CurrentRunningXactsData;
 
    ProcArrayStruct *arrayP = procArray;
    TransactionId *other_xids = ProcGlobal->xids;
    RunningTransactions CurrentRunningXacts = &CurrentRunningXactsData;
    TransactionId latestCompletedXid;
    TransactionId oldestRunningXid;
    TransactionId oldestDatabaseRunningXid;
    TransactionId *xids;
    int         index;
    int         count;
    int         subcount;
    bool        suboverflowed;
 
    Assert(!RecoveryInProgress());
 
    /*
     * Allocating space for maxProcs xids is usually overkill; numProcs would
     * be sufficient.  But it seems better to do the malloc while not holding
     * the lock, so we can't look at numProcs.  Likewise, we allocate much
     * more subxip storage than is probably needed.
     *
     * Should only be allocated in bgwriter, since only ever executed during
     * checkpoints.
     */
    if (CurrentRunningXacts->xids == NULL)
    {
        /*
         * First call
         */
        CurrentRunningXacts->xids = (TransactionId *)
            malloc(TOTAL_MAX_CACHED_SUBXIDS * sizeof(TransactionId));
        if (CurrentRunningXacts->xids == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
    }
 
    xids = CurrentRunningXacts->xids;
 
    count = subcount = 0;
    suboverflowed = false;
 
    /*
     * Ensure that no xids enter or leave the procarray while we obtain
     * snapshot.
     */
    LWLockAcquire(ProcArrayLock, LW_SHARED);
    LWLockAcquire(XidGenLock, LW_SHARED);
 
    latestCompletedXid =
        XidFromFullTransactionId(TransamVariables->latestCompletedXid);
    oldestDatabaseRunningXid = oldestRunningXid =
        XidFromFullTransactionId(TransamVariables->nextXid);
 
    /*
     * Spin over procArray collecting all xids
     */
    for (index = 0; index < arrayP->numProcs; index++)
    {
        TransactionId xid;
 
        /* Fetch xid just once - see GetNewTransactionId */
        xid = UINT32_ACCESS_ONCE(other_xids[index]);
 
        /*
         * We don't need to store transactions that don't have a TransactionId
         * yet because they will not show as running on a standby server.
         */
        if (!TransactionIdIsValid(xid))
            continue;
 
        /*
         * Be careful not to exclude any xids before calculating the values of
         * oldestRunningXid and suboverflowed, since these are used to clean
         * up transaction information held on standbys.
         */
        if (TransactionIdPrecedes(xid, oldestRunningXid))
            oldestRunningXid = xid;
 
        /*
         * Also, update the oldest running xid within the current database. As
         * fetching pgprocno and PGPROC could cause cache misses, we do cheap
         * TransactionId comparison first.
         */
        if (TransactionIdPrecedes(xid, oldestDatabaseRunningXid))
        {
            int         pgprocno = arrayP->pgprocnos[index];
            PGPROC     *proc = &allProcs[pgprocno];
 
            if (proc->databaseId == MyDatabaseId)
                oldestDatabaseRunningXid = xid;
        }
 
        if (ProcGlobal->subxidStates[index].overflowed)
            suboverflowed = true;
 
        /*
         * If we wished to exclude xids this would be the right place for it.
         * Procs with the PROC_IN_VACUUM flag set don't usually assign xids,
         * but they do during truncation at the end when they get the lock and
         * truncate, so it is not much of a problem to include them if they
         * are seen and it is cleaner to include them.
         */
 
        xids[count++] = xid;
    }
 
    /*
     * Spin over procArray collecting all subxids, but only if there hasn't
     * been a suboverflow.
     */
    if (!suboverflowed)
    {
        XidCacheStatus *other_subxidstates = ProcGlobal->subxidStates;
 
        for (index = 0; index < arrayP->numProcs; index++)
        {
            int         pgprocno = arrayP->pgprocnos[index];
            PGPROC     *proc = &allProcs[pgprocno];
            int         nsubxids;
 
            /*
             * Save subtransaction XIDs. Other backends can't add or remove
             * entries while we're holding XidGenLock.
             */
            nsubxids = other_subxidstates[index].count;
            if (nsubxids > 0)
            {
                /* barrier not really required, as XidGenLock is held, but ... */
                pg_read_barrier();  /* pairs with GetNewTransactionId */
 
                memcpy(&xids[count], proc->subxids.xids,
                       nsubxids * sizeof(TransactionId));
                count += nsubxids;
                subcount += nsubxids;
 
                /*
                 * Top-level XID of a transaction is always less than any of
                 * its subxids, so we don't need to check if any of the
                 * subxids are smaller than oldestRunningXid
                 */
            }
        }
    }
 
    /*
     * It's important *not* to include the limits set by slots here because
     * snapbuild.c uses oldestRunningXid to manage its xmin horizon. If those
     * were to be included here the initial value could never increase because
     * of a circular dependency where slots only increase their limits when
     * running xacts increases oldestRunningXid and running xacts only
     * increases if slots do.
     */
 
    CurrentRunningXacts->xcnt = count - subcount;
    CurrentRunningXacts->subxcnt = subcount;
    CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY;
    CurrentRunningXacts->nextXid = XidFromFullTransactionId(TransamVariables->nextXid);
    CurrentRunningXacts->oldestRunningXid = oldestRunningXid;
    CurrentRunningXacts->oldestDatabaseRunningXid = oldestDatabaseRunningXid;
    CurrentRunningXacts->latestCompletedXid = latestCompletedXid;
 
    Assert(TransactionIdIsValid(CurrentRunningXacts->nextXid));
    Assert(TransactionIdIsValid(CurrentRunningXacts->oldestRunningXid));
    Assert(TransactionIdIsNormal(CurrentRunningXacts->latestCompletedXid));
 
    /* We don't release the locks here, the caller is responsible for that */
 
    return CurrentRunningXacts;
}

References allProcs, Assert, XidCacheStatus::count, PGPROC::databaseId, ereport, errcode(), errmsg, ERROR, TransamVariablesData::latestCompletedXid, RunningTransactionsData::latestCompletedXid, LW_SHARED, LWLockAcquire(), malloc, MyDatabaseId, TransamVariablesData::nextXid, RunningTransactionsData::nextXid, ProcArrayStruct::numProcs, RunningTransactionsData::oldestDatabaseRunningXid, RunningTransactionsData::oldestRunningXid, XidCacheStatus::overflowed, pg_read_barrier, ProcArrayStruct::pgprocnos, procArray, ProcGlobal, RecoveryInProgress(), RunningTransactionsData::subxcnt, RunningTransactionsData::subxid_status, PGPROC::subxids, SUBXIDS_IN_ARRAY, SUBXIDS_IN_SUBTRANS, PROC_HDR::subxidStates, TOTAL_MAX_CACHED_SUBXIDS, TransactionIdIsNormal, TransactionIdIsValid, TransactionIdPrecedes(), TransamVariables, UINT32_ACCESS_ONCE, RunningTransactionsData::xcnt, XidFromFullTransactionId, XidCache::xids, PROC_HDR::xids, and RunningTransactionsData::xids.

Referenced by GetStrictOldestNonRemovableTransactionId(), and LogStandbySnapshot().

GetSnapshotData()

Snapshot GetSnapshotData ( Snapshot  snapshot )

extern

Definition at line 2122 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    TransactionId *other_xids = ProcGlobal->xids;
    TransactionId xmin;
    TransactionId xmax;
    int         count = 0;
    int         subcount = 0;
    bool        suboverflowed = false;
    FullTransactionId latest_completed;
    TransactionId oldestxid;
    int         mypgxactoff;
    TransactionId myxid;
    uint64      curXactCompletionCount;
 
    TransactionId replication_slot_xmin = InvalidTransactionId;
    TransactionId replication_slot_catalog_xmin = InvalidTransactionId;
 
    Assert(snapshot != NULL);
 
    /*
     * Allocating space for maxProcs xids is usually overkill; numProcs would
     * be sufficient.  But it seems better to do the malloc while not holding
     * the lock, so we can't look at numProcs.  Likewise, we allocate much
     * more subxip storage than is probably needed.
     *
     * This does open a possibility for avoiding repeated malloc/free: since
     * maxProcs does not change at runtime, we can simply reuse the previous
     * xip arrays if any.  (This relies on the fact that all callers pass
     * static SnapshotData structs.)
     */
    if (snapshot->xip == NULL)
    {
        /*
         * First call for this snapshot. Snapshot is same size whether or not
         * we are in recovery, see later comments.
         */
        snapshot->xip = (TransactionId *)
            malloc(GetMaxSnapshotXidCount() * sizeof(TransactionId));
        if (snapshot->xip == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
        Assert(snapshot->subxip == NULL);
        snapshot->subxip = (TransactionId *)
            malloc(GetMaxSnapshotSubxidCount() * sizeof(TransactionId));
        if (snapshot->subxip == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
    }
 
    /*
     * It is sufficient to get shared lock on ProcArrayLock, even if we are
     * going to set MyProc->xmin.
     */
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    if (GetSnapshotDataReuse(snapshot))
    {
        LWLockRelease(ProcArrayLock);
        return snapshot;
    }
 
    latest_completed = TransamVariables->latestCompletedXid;
    mypgxactoff = MyProc->pgxactoff;
    myxid = other_xids[mypgxactoff];
    Assert(myxid == MyProc->xid);
 
    oldestxid = TransamVariables->oldestXid;
    curXactCompletionCount = TransamVariables->xactCompletionCount;
 
    /* xmax is always latestCompletedXid + 1 */
    xmax = XidFromFullTransactionId(latest_completed);
    TransactionIdAdvance(xmax);
    Assert(TransactionIdIsNormal(xmax));
 
    /* initialize xmin calculation with xmax */
    xmin = xmax;
 
    /* take own xid into account, saves a check inside the loop */
    if (TransactionIdIsNormal(myxid) && NormalTransactionIdPrecedes(myxid, xmin))
        xmin = myxid;
 
    snapshot->takenDuringRecovery = RecoveryInProgress();
 
    if (!snapshot->takenDuringRecovery)
    {
        int         numProcs = arrayP->numProcs;
        TransactionId *xip = snapshot->xip;
        int        *pgprocnos = arrayP->pgprocnos;
        XidCacheStatus *subxidStates = ProcGlobal->subxidStates;
        uint8      *allStatusFlags = ProcGlobal->statusFlags;
 
        /*
         * First collect set of pgxactoff/xids that need to be included in the
         * snapshot.
         */
        for (int pgxactoff = 0; pgxactoff < numProcs; pgxactoff++)
        {
            /* Fetch xid just once - see GetNewTransactionId */
            TransactionId xid = UINT32_ACCESS_ONCE(other_xids[pgxactoff]);
            uint8       statusFlags;
 
            Assert(allProcs[arrayP->pgprocnos[pgxactoff]].pgxactoff == pgxactoff);
 
            /*
             * If the transaction has no XID assigned, we can skip it; it
             * won't have sub-XIDs either.
             */
            if (likely(xid == InvalidTransactionId))
                continue;
 
            /*
             * We don't include our own XIDs (if any) in the snapshot. It
             * needs to be included in the xmin computation, but we did so
             * outside the loop.
             */
            if (pgxactoff == mypgxactoff)
                continue;
 
            /*
             * The only way we are able to get here with a non-normal xid is
             * during bootstrap - with this backend using
             * BootstrapTransactionId. But the above test should filter that
             * out.
             */
            Assert(TransactionIdIsNormal(xid));
 
            /*
             * If the XID is >= xmax, we can skip it; such transactions will
             * be treated as running anyway (and any sub-XIDs will also be >=
             * xmax).
             */
            if (!NormalTransactionIdPrecedes(xid, xmax))
                continue;
 
            /*
             * Skip over backends doing logical decoding which manages xmin
             * separately (check below) and ones running LAZY VACUUM.
             */
            statusFlags = allStatusFlags[pgxactoff];
            if (statusFlags & (PROC_IN_LOGICAL_DECODING | PROC_IN_VACUUM))
                continue;
 
            if (NormalTransactionIdPrecedes(xid, xmin))
                xmin = xid;
 
            /* Add XID to snapshot. */
            xip[count++] = xid;
 
            /*
             * Save subtransaction XIDs if possible (if we've already
             * overflowed, there's no point).  Note that the subxact XIDs must
             * be later than their parent, so no need to check them against
             * xmin.  We could filter against xmax, but it seems better not to
             * do that much work while holding the ProcArrayLock.
             *
             * The other backend can add more subxids concurrently, but cannot
             * remove any.  Hence it's important to fetch nxids just once.
             * Should be safe to use memcpy, though.  (We needn't worry about
             * missing any xids added concurrently, because they must postdate
             * xmax.)
             *
             * Again, our own XIDs are not included in the snapshot.
             */
            if (!suboverflowed)
            {
 
                if (subxidStates[pgxactoff].overflowed)
                    suboverflowed = true;
                else
                {
                    int         nsubxids = subxidStates[pgxactoff].count;
 
                    if (nsubxids > 0)
                    {
                        int         pgprocno = pgprocnos[pgxactoff];
                        PGPROC     *proc = &allProcs[pgprocno];
 
                        pg_read_barrier();  /* pairs with GetNewTransactionId */
 
                        memcpy(snapshot->subxip + subcount,
                               proc->subxids.xids,
                               nsubxids * sizeof(TransactionId));
                        subcount += nsubxids;
                    }
                }
            }
        }
    }
    else
    {
        /*
         * We're in hot standby, so get XIDs from KnownAssignedXids.
         *
         * We store all xids directly into subxip[]. Here's why:
         *
         * In recovery we don't know which xids are top-level and which are
         * subxacts, a design choice that greatly simplifies xid processing.
         *
         * It seems like we would want to try to put xids into xip[] only, but
         * that is fairly small. We would either need to make that bigger or
         * to increase the rate at which we WAL-log xid assignment; neither is
         * an appealing choice.
         *
         * We could try to store xids into xip[] first and then into subxip[]
         * if there are too many xids. That only works if the snapshot doesn't
         * overflow because we do not search subxip[] in that case. A simpler
         * way is to just store all xids in the subxip array because this is
         * by far the bigger array. We just leave the xip array empty.
         *
         * Either way we need to change the way XidInMVCCSnapshot() works
         * depending upon when the snapshot was taken, or change normal
         * snapshot processing so it matches.
         *
         * Note: It is possible for recovery to end before we finish taking
         * the snapshot, and for newly assigned transaction ids to be added to
         * the ProcArray.  xmax cannot change while we hold ProcArrayLock, so
         * those newly added transaction ids would be filtered away, so we
         * need not be concerned about them.
         */
        subcount = KnownAssignedXidsGetAndSetXmin(snapshot->subxip, &xmin,
                                                  xmax);
 
        if (TransactionIdPrecedesOrEquals(xmin, procArray->lastOverflowedXid))
            suboverflowed = true;
    }
 
 
    /*
     * Fetch into local variable while ProcArrayLock is held - the
     * LWLockRelease below is a barrier, ensuring this happens inside the
     * lock.
     */
    replication_slot_xmin = procArray->replication_slot_xmin;
    replication_slot_catalog_xmin = procArray->replication_slot_catalog_xmin;
 
    if (!TransactionIdIsValid(MyProc->xmin))
        MyProc->xmin = TransactionXmin = xmin;
 
    LWLockRelease(ProcArrayLock);
 
    /* maintain state for GlobalVis* */
    {
        TransactionId def_vis_xid;
        TransactionId def_vis_xid_data;
        FullTransactionId def_vis_fxid;
        FullTransactionId def_vis_fxid_data;
        FullTransactionId oldestfxid;
 
        /*
         * Converting oldestXid is only safe when xid horizon cannot advance,
         * i.e. holding locks. While we don't hold the lock anymore, all the
         * necessary data has been gathered with lock held.
         */
        oldestfxid = FullXidRelativeTo(latest_completed, oldestxid);
 
        /* Check whether there's a replication slot requiring an older xmin. */
        def_vis_xid_data =
            TransactionIdOlder(xmin, replication_slot_xmin);
 
        /*
         * Rows in non-shared, non-catalog tables possibly could be vacuumed
         * if older than this xid.
         */
        def_vis_xid = def_vis_xid_data;
 
        /*
         * Check whether there's a replication slot requiring an older catalog
         * xmin.
         */
        def_vis_xid =
            TransactionIdOlder(replication_slot_catalog_xmin, def_vis_xid);
 
        def_vis_fxid = FullXidRelativeTo(latest_completed, def_vis_xid);
        def_vis_fxid_data = FullXidRelativeTo(latest_completed, def_vis_xid_data);
 
        /*
         * Check if we can increase upper bound. As a previous
         * GlobalVisUpdate() might have computed more aggressive values, don't
         * overwrite them if so.
         */
        GlobalVisSharedRels.definitely_needed =
            FullTransactionIdNewer(def_vis_fxid,
                                   GlobalVisSharedRels.definitely_needed);
        GlobalVisCatalogRels.definitely_needed =
            FullTransactionIdNewer(def_vis_fxid,
                                   GlobalVisCatalogRels.definitely_needed);
        GlobalVisDataRels.definitely_needed =
            FullTransactionIdNewer(def_vis_fxid_data,
                                   GlobalVisDataRels.definitely_needed);
        /* See temp_oldest_nonremovable computation in ComputeXidHorizons() */
        if (TransactionIdIsNormal(myxid))
            GlobalVisTempRels.definitely_needed =
                FullXidRelativeTo(latest_completed, myxid);
        else
        {
            GlobalVisTempRels.definitely_needed = latest_completed;
            FullTransactionIdAdvance(&GlobalVisTempRels.definitely_needed);
        }
 
        /*
         * Check if we know that we can initialize or increase the lower
         * bound. Currently the only cheap way to do so is to use
         * TransamVariables->oldestXid as input.
         *
         * We should definitely be able to do better. We could e.g. put a
         * global lower bound value into TransamVariables.
         */
        GlobalVisSharedRels.maybe_needed =
            FullTransactionIdNewer(GlobalVisSharedRels.maybe_needed,
                                   oldestfxid);
        GlobalVisCatalogRels.maybe_needed =
            FullTransactionIdNewer(GlobalVisCatalogRels.maybe_needed,
                                   oldestfxid);
        GlobalVisDataRels.maybe_needed =
            FullTransactionIdNewer(GlobalVisDataRels.maybe_needed,
                                   oldestfxid);
        /* accurate value known */
        GlobalVisTempRels.maybe_needed = GlobalVisTempRels.definitely_needed;
    }
 
    RecentXmin = xmin;
    Assert(TransactionIdPrecedesOrEquals(TransactionXmin, RecentXmin));
 
    snapshot->xmin = xmin;
    snapshot->xmax = xmax;
    snapshot->xcnt = count;
    snapshot->subxcnt = subcount;
    snapshot->suboverflowed = suboverflowed;
    snapshot->snapXactCompletionCount = curXactCompletionCount;
 
    snapshot->curcid = GetCurrentCommandId(false);
 
    /*
     * This is a new snapshot, so set both refcounts are zero, and mark it as
     * not copied in persistent memory.
     */
    snapshot->active_count = 0;
    snapshot->regd_count = 0;
    snapshot->copied = false;
 
    return snapshot;
}

References SnapshotData::active_count, allProcs, Assert, SnapshotData::copied, XidCacheStatus::count, SnapshotData::curcid, GlobalVisState::definitely_needed, ereport, errcode(), errmsg, ERROR, FullTransactionIdAdvance(), FullTransactionIdNewer(), FullXidRelativeTo(), GetCurrentCommandId(), GetMaxSnapshotSubxidCount(), GetMaxSnapshotXidCount(), GetSnapshotDataReuse(), GlobalVisCatalogRels, GlobalVisDataRels, GlobalVisSharedRels, GlobalVisTempRels, InvalidTransactionId, KnownAssignedXidsGetAndSetXmin(), ProcArrayStruct::lastOverflowedXid, TransamVariablesData::latestCompletedXid, likely, LW_SHARED, LWLockAcquire(), LWLockRelease(), malloc, GlobalVisState::maybe_needed, MyProc, NormalTransactionIdPrecedes, ProcArrayStruct::numProcs, TransamVariablesData::oldestXid, pg_read_barrier, ProcArrayStruct::pgprocnos, PGPROC::pgxactoff, PROC_IN_LOGICAL_DECODING, PROC_IN_VACUUM, procArray, ProcGlobal, RecentXmin, RecoveryInProgress(), SnapshotData::regd_count, ProcArrayStruct::replication_slot_catalog_xmin, ProcArrayStruct::replication_slot_xmin, SnapshotData::snapXactCompletionCount, PROC_HDR::statusFlags, SnapshotData::suboverflowed, SnapshotData::subxcnt, PGPROC::subxids, PROC_HDR::subxidStates, SnapshotData::subxip, SnapshotData::takenDuringRecovery, TransactionIdAdvance, TransactionIdIsNormal, TransactionIdIsValid, TransactionIdOlder(), TransactionIdPrecedesOrEquals(), TransactionXmin, TransamVariables, UINT32_ACCESS_ONCE, TransamVariablesData::xactCompletionCount, SnapshotData::xcnt, PGPROC::xid, XidFromFullTransactionId, XidCache::xids, PROC_HDR::xids, SnapshotData::xip, SnapshotData::xmax, PGPROC::xmin, and SnapshotData::xmin.

Referenced by GetLatestSnapshot(), GetNonHistoricCatalogSnapshot(), GetSerializableTransactionSnapshotInt(), GetTransactionSnapshot(), and SetTransactionSnapshot().

GetVirtualXIDsDelayingChkpt()

VirtualTransactionId * GetVirtualXIDsDelayingChkpt ( int *  nvxids, int  type  )

extern

Definition at line 3004 of file procarray.c.

{
    VirtualTransactionId *vxids;
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    Assert(type != 0);
 
    /* allocate what's certainly enough result space */
    vxids = palloc_array(VirtualTransactionId, arrayP->maxProcs);
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        if ((proc->delayChkptFlags & type) != 0)
        {
            VirtualTransactionId vxid;
 
            GET_VXID_FROM_PGPROC(vxid, *proc);
            if (VirtualTransactionIdIsValid(vxid))
                vxids[count++] = vxid;
        }
    }
 
    LWLockRelease(ProcArrayLock);
 
    *nvxids = count;
    return vxids;
}

References allProcs, Assert, PGPROC::delayChkptFlags, GET_VXID_FROM_PGPROC, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::maxProcs, ProcArrayStruct::numProcs, palloc_array, ProcArrayStruct::pgprocnos, procArray, type, and VirtualTransactionIdIsValid.

Referenced by CreateCheckPoint().

HaveVirtualXIDsDelayingChkpt()

bool HaveVirtualXIDsDelayingChkpt ( VirtualTransactionId *  vxids, int  nvxids, int  type  )

extern

Definition at line 3049 of file procarray.c.

{
    bool        result = false;
    ProcArrayStruct *arrayP = procArray;
    int         index;
 
    Assert(type != 0);
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
        VirtualTransactionId vxid;
 
        GET_VXID_FROM_PGPROC(vxid, *proc);
 
        if ((proc->delayChkptFlags & type) != 0 &&
            VirtualTransactionIdIsValid(vxid))
        {
            int         i;
 
            for (i = 0; i < nvxids; i++)
            {
                if (VirtualTransactionIdEquals(vxid, vxids[i]))
                {
                    result = true;
                    break;
                }
            }
            if (result)
                break;
        }
    }
 
    LWLockRelease(ProcArrayLock);
 
    return result;
}

References allProcs, Assert, PGPROC::delayChkptFlags, GET_VXID_FROM_PGPROC, i, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, procArray, type, VirtualTransactionIdEquals, and VirtualTransactionIdIsValid.

Referenced by CreateCheckPoint().

IsBackendPid()

bool IsBackendPid ( int  pid )

extern

Definition at line 3251 of file procarray.c.

{
    return (BackendPidGetProc(pid) != NULL);
}

References BackendPidGetProc().

Referenced by pg_stat_get_subscription().

KnownAssignedTransactionIdsIdleMaintenance()

void KnownAssignedTransactionIdsIdleMaintenance ( void  )

extern

Definition at line 4571 of file procarray.c.

{
    KnownAssignedXidsCompress(KAX_STARTUP_PROCESS_IDLE, false);
}

References KAX_STARTUP_PROCESS_IDLE, and KnownAssignedXidsCompress().

Referenced by WaitForWALToBecomeAvailable().

MinimumActiveBackends()

bool MinimumActiveBackends ( int  min )

extern

Definition at line 3576 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         count = 0;
    int         index;
 
    /* Quick short-circuit if no minimum is specified */
    if (min == 0)
        return true;
 
    /*
     * Note: for speed, we don't acquire ProcArrayLock.  This is a little bit
     * bogus, but since we are only testing fields for zero or nonzero, it
     * should be OK.  The result is only used for heuristic purposes anyway...
     */
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        /*
         * Since we're not holding a lock, need to be prepared to deal with
         * garbage, as someone could have incremented numProcs but not yet
         * filled the structure.
         *
         * If someone just decremented numProcs, 'proc' could also point to a
         * PGPROC entry that's no longer in the array. It still points to a
         * PGPROC struct, though, because freed PGPROC entries just go to the
         * free list and are recycled. Its contents are nonsense in that case,
         * but that's acceptable for this function.
         */
        if (pgprocno == -1)
            continue;           /* do not count deleted entries */
        if (proc == MyProc)
            continue;           /* do not count myself */
        if (proc->xid == InvalidTransactionId)
            continue;           /* do not count if no XID assigned */
        if (proc->pid == 0)
            continue;           /* do not count prepared xacts */
        if (proc->waitLock != NULL)
            continue;           /* do not count if blocked on a lock */
        count++;
        if (count >= min)
            break;
    }
 
    return count >= min;
}

References allProcs, InvalidTransactionId, MyProc, ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, PGPROC::waitLock, and PGPROC::xid.

Referenced by XLogFlush().

ProcArrayAdd()

void ProcArrayAdd ( PGPROC *  proc )

extern

Definition at line 472 of file procarray.c.

{
    int         pgprocno = GetNumberFromPGProc(proc);
    ProcArrayStruct *arrayP = procArray;
    int         index;
    int         movecount;
 
    /* See ProcGlobal comment explaining why both locks are held */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
    LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
 
    if (arrayP->numProcs >= arrayP->maxProcs)
    {
        /*
         * Oops, no room.  (This really shouldn't happen, since there is a
         * fixed supply of PGPROC structs too, and so we should have failed
         * earlier.)
         */
        ereport(FATAL,
                (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
                 errmsg("sorry, too many clients already")));
    }
 
    /*
     * Keep the procs array sorted by (PGPROC *) so that we can utilize
     * locality of references much better. This is useful while traversing the
     * ProcArray because there is an increased likelihood of finding the next
     * PGPROC structure in the cache.
     *
     * Since the occurrence of adding/removing a proc is much lower than the
     * access to the ProcArray itself, the overhead should be marginal
     */
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         this_procno = arrayP->pgprocnos[index];
 
        Assert(this_procno >= 0 && this_procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS));
        Assert(allProcs[this_procno].pgxactoff == index);
 
        /* If we have found our right position in the array, break */
        if (this_procno > pgprocno)
            break;
    }
 
    movecount = arrayP->numProcs - index;
    memmove(&arrayP->pgprocnos[index + 1],
            &arrayP->pgprocnos[index],
            movecount * sizeof(*arrayP->pgprocnos));
    memmove(&ProcGlobal->xids[index + 1],
            &ProcGlobal->xids[index],
            movecount * sizeof(*ProcGlobal->xids));
    memmove(&ProcGlobal->subxidStates[index + 1],
            &ProcGlobal->subxidStates[index],
            movecount * sizeof(*ProcGlobal->subxidStates));
    memmove(&ProcGlobal->statusFlags[index + 1],
            &ProcGlobal->statusFlags[index],
            movecount * sizeof(*ProcGlobal->statusFlags));
 
    arrayP->pgprocnos[index] = GetNumberFromPGProc(proc);
    proc->pgxactoff = index;
    ProcGlobal->xids[index] = proc->xid;
    ProcGlobal->subxidStates[index] = proc->subxidStatus;
    ProcGlobal->statusFlags[index] = proc->statusFlags;
 
    arrayP->numProcs++;
 
    /* adjust pgxactoff for all following PGPROCs */
    index++;
    for (; index < arrayP->numProcs; index++)
    {
        int         procno = arrayP->pgprocnos[index];
 
        Assert(procno >= 0 && procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS));
        Assert(allProcs[procno].pgxactoff == index - 1);
 
        allProcs[procno].pgxactoff = index;
    }
 
    /*
     * Release in reversed acquisition order, to reduce frequency of having to
     * wait for XidGenLock while holding ProcArrayLock.
     */
    LWLockRelease(XidGenLock);
    LWLockRelease(ProcArrayLock);
}

References allProcs, Assert, ereport, errcode(), errmsg, FATAL, GetNumberFromPGProc, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::maxProcs, NUM_AUXILIARY_PROCS, ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PGPROC::pgxactoff, procArray, ProcGlobal, PGPROC::statusFlags, PROC_HDR::statusFlags, PROC_HDR::subxidStates, PGPROC::subxidStatus, PGPROC::xid, and PROC_HDR::xids.

Referenced by InitProcessPhase2(), and MarkAsPrepared().

ProcArrayApplyRecoveryInfo()

void ProcArrayApplyRecoveryInfo ( RunningTransactions  running )

extern

Definition at line 1053 of file procarray.c.

{
    TransactionId *xids;
    TransactionId advanceNextXid;
    int         nxids;
    int         i;
 
    Assert(standbyState >= STANDBY_INITIALIZED);
    Assert(TransactionIdIsValid(running->nextXid));
    Assert(TransactionIdIsValid(running->oldestRunningXid));
    Assert(TransactionIdIsNormal(running->latestCompletedXid));
 
    /*
     * Remove stale transactions, if any.
     */
    ExpireOldKnownAssignedTransactionIds(running->oldestRunningXid);
 
    /*
     * Adjust TransamVariables->nextXid before StandbyReleaseOldLocks(),
     * because we will need it up to date for accessing two-phase transactions
     * in StandbyReleaseOldLocks().
     */
    advanceNextXid = running->nextXid;
    TransactionIdRetreat(advanceNextXid);
    AdvanceNextFullTransactionIdPastXid(advanceNextXid);
    Assert(FullTransactionIdIsValid(TransamVariables->nextXid));
 
    /*
     * Remove stale locks, if any.
     */
    StandbyReleaseOldLocks(running->oldestRunningXid);
 
    /*
     * If our snapshot is already valid, nothing else to do...
     */
    if (standbyState == STANDBY_SNAPSHOT_READY)
        return;
 
    /*
     * If our initial RunningTransactionsData had an overflowed snapshot then
     * we knew we were missing some subxids from our snapshot. If we continue
     * to see overflowed snapshots then we might never be able to start up, so
     * we make another test to see if our snapshot is now valid. We know that
     * the missing subxids are equal to or earlier than nextXid. After we
     * initialise we continue to apply changes during recovery, so once the
     * oldestRunningXid is later than the nextXid from the initial snapshot we
     * know that we no longer have missing information and can mark the
     * snapshot as valid.
     */
    if (standbyState == STANDBY_SNAPSHOT_PENDING)
    {
        /*
         * If the snapshot isn't overflowed or if its empty we can reset our
         * pending state and use this snapshot instead.
         */
        if (running->subxid_status != SUBXIDS_MISSING || running->xcnt == 0)
        {
            /*
             * If we have already collected known assigned xids, we need to
             * throw them away before we apply the recovery snapshot.
             */
            KnownAssignedXidsReset();
            standbyState = STANDBY_INITIALIZED;
        }
        else
        {
            if (TransactionIdPrecedes(standbySnapshotPendingXmin,
                                      running->oldestRunningXid))
            {
                standbyState = STANDBY_SNAPSHOT_READY;
                elog(DEBUG1,
                     "recovery snapshots are now enabled");
            }
            else
                elog(DEBUG1,
                     "recovery snapshot waiting for non-overflowed snapshot or "
                     "until oldest active xid on standby is at least %u (now %u)",
                     standbySnapshotPendingXmin,
                     running->oldestRunningXid);
            return;
        }
    }
 
    Assert(standbyState == STANDBY_INITIALIZED);
 
    /*
     * NB: this can be reached at least twice, so make sure new code can deal
     * with that.
     */
 
    /*
     * Nobody else is running yet, but take locks anyhow
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    /*
     * KnownAssignedXids is sorted so we cannot just add the xids, we have to
     * sort them first.
     *
     * Some of the new xids are top-level xids and some are subtransactions.
     * We don't call SubTransSetParent because it doesn't matter yet. If we
     * aren't overflowed then all xids will fit in snapshot and so we don't
     * need subtrans. If we later overflow, an xid assignment record will add
     * xids to subtrans. If RunningTransactionsData is overflowed then we
     * don't have enough information to correctly update subtrans anyway.
     */
 
    /*
     * Allocate a temporary array to avoid modifying the array passed as
     * argument.
     */
    xids = palloc_array(TransactionId, running->xcnt + running->subxcnt);
 
    /*
     * Add to the temp array any xids which have not already completed.
     */
    nxids = 0;
    for (i = 0; i < running->xcnt + running->subxcnt; i++)
    {
        TransactionId xid = running->xids[i];
 
        /*
         * The running-xacts snapshot can contain xids that were still visible
         * in the procarray when the snapshot was taken, but were already
         * WAL-logged as completed. They're not running anymore, so ignore
         * them.
         */
        if (TransactionIdDidCommit(xid) || TransactionIdDidAbort(xid))
            continue;
 
        xids[nxids++] = xid;
    }
 
    if (nxids > 0)
    {
        if (procArray->numKnownAssignedXids != 0)
        {
            LWLockRelease(ProcArrayLock);
            elog(ERROR, "KnownAssignedXids is not empty");
        }
 
        /*
         * Sort the array so that we can add them safely into
         * KnownAssignedXids.
         *
         * We have to sort them logically, because in KnownAssignedXidsAdd we
         * call TransactionIdFollowsOrEquals and so on. But we know these XIDs
         * come from RUNNING_XACTS, which means there are only normal XIDs
         * from the same epoch, so this is safe.
         */
        qsort(xids, nxids, sizeof(TransactionId), xidLogicalComparator);
 
        /*
         * Add the sorted snapshot into KnownAssignedXids.  The running-xacts
         * snapshot may include duplicated xids because of prepared
         * transactions, so ignore them.
         */
        for (i = 0; i < nxids; i++)
        {
            if (i > 0 && TransactionIdEquals(xids[i - 1], xids[i]))
            {
                elog(DEBUG1,
                     "found duplicated transaction %u for KnownAssignedXids insertion",
                     xids[i]);
                continue;
            }
            KnownAssignedXidsAdd(xids[i], xids[i], true);
        }
 
        KnownAssignedXidsDisplay(DEBUG3);
    }
 
    pfree(xids);
 
    /*
     * latestObservedXid is at least set to the point where SUBTRANS was
     * started up to (cf. ProcArrayInitRecovery()) or to the biggest xid
     * RecordKnownAssignedTransactionIds() was called for.  Initialize
     * subtrans from thereon, up to nextXid - 1.
     *
     * We need to duplicate parts of RecordKnownAssignedTransactionId() here,
     * because we've just added xids to the known assigned xids machinery that
     * haven't gone through RecordKnownAssignedTransactionId().
     */
    Assert(TransactionIdIsNormal(latestObservedXid));
    TransactionIdAdvance(latestObservedXid);
    while (TransactionIdPrecedes(latestObservedXid, running->nextXid))
    {
        ExtendSUBTRANS(latestObservedXid);
        TransactionIdAdvance(latestObservedXid);
    }
    TransactionIdRetreat(latestObservedXid);    /* = running->nextXid - 1 */
 
    /* ----------
     * Now we've got the running xids we need to set the global values that
     * are used to track snapshots as they evolve further.
     *
     * - latestCompletedXid which will be the xmax for snapshots
     * - lastOverflowedXid which shows whether snapshots overflow
     * - nextXid
     *
     * If the snapshot overflowed, then we still initialise with what we know,
     * but the recovery snapshot isn't fully valid yet because we know there
     * are some subxids missing. We don't know the specific subxids that are
     * missing, so conservatively assume the last one is latestObservedXid.
     * ----------
     */
    if (running->subxid_status == SUBXIDS_MISSING)
    {
        standbyState = STANDBY_SNAPSHOT_PENDING;
 
        standbySnapshotPendingXmin = latestObservedXid;
        procArray->lastOverflowedXid = latestObservedXid;
    }
    else
    {
        standbyState = STANDBY_SNAPSHOT_READY;
 
        standbySnapshotPendingXmin = InvalidTransactionId;
 
        /*
         * If the 'xids' array didn't include all subtransactions, we have to
         * mark any snapshots taken as overflowed.
         */
        if (running->subxid_status == SUBXIDS_IN_SUBTRANS)
            procArray->lastOverflowedXid = latestObservedXid;
        else
        {
            Assert(running->subxid_status == SUBXIDS_IN_ARRAY);
            procArray->lastOverflowedXid = InvalidTransactionId;
        }
    }
 
    /*
     * If a transaction wrote a commit record in the gap between taking and
     * logging the snapshot then latestCompletedXid may already be higher than
     * the value from the snapshot, so check before we use the incoming value.
     * It also might not yet be set at all.
     */
    MaintainLatestCompletedXidRecovery(running->latestCompletedXid);
 
    /*
     * NB: No need to increment TransamVariables->xactCompletionCount here,
     * nobody can see it yet.
     */
 
    LWLockRelease(ProcArrayLock);
 
    KnownAssignedXidsDisplay(DEBUG3);
    if (standbyState == STANDBY_SNAPSHOT_READY)
        elog(DEBUG1, "recovery snapshots are now enabled");
    else
        elog(DEBUG1,
             "recovery snapshot waiting for non-overflowed snapshot or "
             "until oldest active xid on standby is at least %u (now %u)",
             standbySnapshotPendingXmin,
             running->oldestRunningXid);
}

References AdvanceNextFullTransactionIdPastXid(), Assert, DEBUG1, DEBUG3, elog, ERROR, ExpireOldKnownAssignedTransactionIds(), ExtendSUBTRANS(), FullTransactionIdIsValid, i, InvalidTransactionId, KnownAssignedXidsAdd(), KnownAssignedXidsDisplay(), KnownAssignedXidsReset(), ProcArrayStruct::lastOverflowedXid, RunningTransactionsData::latestCompletedXid, latestObservedXid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaintainLatestCompletedXidRecovery(), TransamVariablesData::nextXid, RunningTransactionsData::nextXid, ProcArrayStruct::numKnownAssignedXids, RunningTransactionsData::oldestRunningXid, palloc_array, pfree(), procArray, qsort, STANDBY_INITIALIZED, STANDBY_SNAPSHOT_PENDING, STANDBY_SNAPSHOT_READY, StandbyReleaseOldLocks(), standbySnapshotPendingXmin, standbyState, RunningTransactionsData::subxcnt, RunningTransactionsData::subxid_status, SUBXIDS_IN_ARRAY, SUBXIDS_IN_SUBTRANS, SUBXIDS_MISSING, TransactionIdAdvance, TransactionIdDidAbort(), TransactionIdDidCommit(), TransactionIdEquals, TransactionIdIsNormal, TransactionIdIsValid, TransactionIdPrecedes(), TransactionIdRetreat, TransamVariables, RunningTransactionsData::xcnt, xidLogicalComparator(), and RunningTransactionsData::xids.

Referenced by standby_redo(), StartupXLOG(), and xlog_redo().

ProcArrayApplyXidAssignment()

void ProcArrayApplyXidAssignment ( TransactionId  topxid, int  nsubxids, TransactionId *  subxids  )

extern

Definition at line 1317 of file procarray.c.

{
    TransactionId max_xid;
    int         i;
 
    Assert(standbyState >= STANDBY_INITIALIZED);
 
    max_xid = TransactionIdLatest(topxid, nsubxids, subxids);
 
    /*
     * Mark all the subtransactions as observed.
     *
     * NOTE: This will fail if the subxid contains too many previously
     * unobserved xids to fit into known-assigned-xids. That shouldn't happen
     * as the code stands, because xid-assignment records should never contain
     * more than PGPROC_MAX_CACHED_SUBXIDS entries.
     */
    RecordKnownAssignedTransactionIds(max_xid);
 
    /*
     * Notice that we update pg_subtrans with the top-level xid, rather than
     * the parent xid. This is a difference between normal processing and
     * recovery, yet is still correct in all cases. The reason is that
     * subtransaction commit is not marked in clog until commit processing, so
     * all aborted subtransactions have already been clearly marked in clog.
     * As a result we are able to refer directly to the top-level
     * transaction's state rather than skipping through all the intermediate
     * states in the subtransaction tree. This should be the first time we
     * have attempted to SubTransSetParent().
     */
    for (i = 0; i < nsubxids; i++)
        SubTransSetParent(subxids[i], topxid);
 
    /* KnownAssignedXids isn't maintained yet, so we're done for now */
    if (standbyState == STANDBY_INITIALIZED)
        return;
 
    /*
     * Uses same locking as transaction commit
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    /*
     * Remove subxids from known-assigned-xacts.
     */
    KnownAssignedXidsRemoveTree(InvalidTransactionId, nsubxids, subxids);
 
    /*
     * Advance lastOverflowedXid to be at least the last of these subxids.
     */
    if (TransactionIdPrecedes(procArray->lastOverflowedXid, max_xid))
        procArray->lastOverflowedXid = max_xid;
 
    LWLockRelease(ProcArrayLock);
}

References Assert, i, InvalidTransactionId, KnownAssignedXidsRemoveTree(), ProcArrayStruct::lastOverflowedXid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), procArray, RecordKnownAssignedTransactionIds(), STANDBY_INITIALIZED, standbyState, SubTransSetParent(), TransactionIdLatest(), and TransactionIdPrecedes().

Referenced by xact_redo().

ProcArrayClearTransaction()

void ProcArrayClearTransaction ( PGPROC *  proc )

extern

Definition at line 907 of file procarray.c.

{
    int         pgxactoff;
 
    /*
     * Currently we need to lock ProcArrayLock exclusively here, as we
     * increment xactCompletionCount below. We also need it at least in shared
     * mode for pgproc->pgxactoff to stay the same below.
     *
     * We could however, as this action does not actually change anyone's view
     * of the set of running XIDs (our entry is duplicate with the gxact that
     * has already been inserted into the ProcArray), lower the lock level to
     * shared if we were to make xactCompletionCount an atomic variable. But
     * that doesn't seem worth it currently, as a 2PC commit is heavyweight
     * enough for this not to be the bottleneck.  If it ever becomes a
     * bottleneck it may also be worth considering to combine this with the
     * subsequent ProcArrayRemove()
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    pgxactoff = proc->pgxactoff;
 
    ProcGlobal->xids[pgxactoff] = InvalidTransactionId;
    proc->xid = InvalidTransactionId;
 
    proc->vxid.lxid = InvalidLocalTransactionId;
    proc->xmin = InvalidTransactionId;
 
    Assert(!(proc->statusFlags & PROC_VACUUM_STATE_MASK));
    Assert(!proc->delayChkptFlags);
 
    /*
     * Need to increment completion count even though transaction hasn't
     * really committed yet. The reason for that is that GetSnapshotData()
     * omits the xid of the current transaction, thus without the increment we
     * otherwise could end up reusing the snapshot later. Which would be bad,
     * because it might not count the prepared transaction as running.
     */
    TransamVariables->xactCompletionCount++;
 
    /* Clear the subtransaction-XID cache too */
    Assert(ProcGlobal->subxidStates[pgxactoff].count == proc->subxidStatus.count &&
           ProcGlobal->subxidStates[pgxactoff].overflowed == proc->subxidStatus.overflowed);
    if (proc->subxidStatus.count > 0 || proc->subxidStatus.overflowed)
    {
        ProcGlobal->subxidStates[pgxactoff].count = 0;
        ProcGlobal->subxidStates[pgxactoff].overflowed = false;
        proc->subxidStatus.count = 0;
        proc->subxidStatus.overflowed = false;
    }
 
    LWLockRelease(ProcArrayLock);
}

References Assert, XidCacheStatus::count, PGPROC::delayChkptFlags, InvalidLocalTransactionId, InvalidTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), PGPROC::lxid, XidCacheStatus::overflowed, PGPROC::pgxactoff, PROC_VACUUM_STATE_MASK, ProcGlobal, PGPROC::statusFlags, PROC_HDR::subxidStates, PGPROC::subxidStatus, TransamVariables, PGPROC::vxid, TransamVariablesData::xactCompletionCount, PGPROC::xid, PROC_HDR::xids, and PGPROC::xmin.

Referenced by PrepareTransaction().

ProcArrayEndTransaction()

void ProcArrayEndTransaction ( PGPROC *  proc, TransactionId  latestXid  )

extern

Definition at line 671 of file procarray.c.

{
    if (TransactionIdIsValid(latestXid))
    {
        /*
         * We must lock ProcArrayLock while clearing our advertised XID, so
         * that we do not exit the set of "running" transactions while someone
         * else is taking a snapshot.  See discussion in
         * src/backend/access/transam/README.
         */
        Assert(TransactionIdIsValid(proc->xid));
 
        /*
         * If we can immediately acquire ProcArrayLock, we clear our own XID
         * and release the lock.  If not, use group XID clearing to improve
         * efficiency.
         */
        if (LWLockConditionalAcquire(ProcArrayLock, LW_EXCLUSIVE))
        {
            ProcArrayEndTransactionInternal(proc, latestXid);
            LWLockRelease(ProcArrayLock);
        }
        else
            ProcArrayGroupClearXid(proc, latestXid);
    }
    else
    {
        /*
         * If we have no XID, we don't need to lock, since we won't affect
         * anyone else's calculation of a snapshot.  We might change their
         * estimate of global xmin, but that's OK.
         */
        Assert(!TransactionIdIsValid(proc->xid));
        Assert(proc->subxidStatus.count == 0);
        Assert(!proc->subxidStatus.overflowed);
 
        proc->vxid.lxid = InvalidLocalTransactionId;
        proc->xmin = InvalidTransactionId;
 
        /* be sure this is cleared in abort */
        proc->delayChkptFlags = 0;
 
        /* must be cleared with xid/xmin: */
        /* avoid unnecessarily dirtying shared cachelines */
        if (proc->statusFlags & PROC_VACUUM_STATE_MASK)
        {
            Assert(!LWLockHeldByMe(ProcArrayLock));
            LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
            Assert(proc->statusFlags == ProcGlobal->statusFlags[proc->pgxactoff]);
            proc->statusFlags &= ~PROC_VACUUM_STATE_MASK;
            ProcGlobal->statusFlags[proc->pgxactoff] = proc->statusFlags;
            LWLockRelease(ProcArrayLock);
        }
    }
}

References Assert, XidCacheStatus::count, PGPROC::delayChkptFlags, InvalidLocalTransactionId, InvalidTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockConditionalAcquire(), LWLockHeldByMe(), LWLockRelease(), PGPROC::lxid, XidCacheStatus::overflowed, PGPROC::pgxactoff, PROC_VACUUM_STATE_MASK, ProcArrayEndTransactionInternal(), ProcArrayGroupClearXid(), ProcGlobal, PGPROC::statusFlags, PROC_HDR::statusFlags, PGPROC::subxidStatus, TransactionIdIsValid, PGPROC::vxid, PGPROC::xid, and PGPROC::xmin.

Referenced by AbortTransaction(), and CommitTransaction().

ProcArrayGetReplicationSlotXmin()

void ProcArrayGetReplicationSlotXmin ( TransactionId *  xmin, TransactionId *  catalog_xmin  )

extern

Definition at line 3975 of file procarray.c.

{
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    if (xmin != NULL)
        *xmin = procArray->replication_slot_xmin;
 
    if (catalog_xmin != NULL)
        *catalog_xmin = procArray->replication_slot_catalog_xmin;
 
    LWLockRelease(ProcArrayLock);
}

References LW_SHARED, LWLockAcquire(), LWLockRelease(), procArray, ProcArrayStruct::replication_slot_catalog_xmin, and ProcArrayStruct::replication_slot_xmin.

Referenced by logical_begin_heap_rewrite().

ProcArrayInitRecovery()

void ProcArrayInitRecovery ( TransactionId  initializedUptoXID )

extern

Definition at line 1022 of file procarray.c.

{
    Assert(standbyState == STANDBY_INITIALIZED);
    Assert(TransactionIdIsNormal(initializedUptoXID));
 
    /*
     * we set latestObservedXid to the xid SUBTRANS has been initialized up
     * to, so we can extend it from that point onwards in
     * RecordKnownAssignedTransactionIds, and when we get consistent in
     * ProcArrayApplyRecoveryInfo().
     */
    latestObservedXid = initializedUptoXID;
    TransactionIdRetreat(latestObservedXid);
}

References Assert, latestObservedXid, STANDBY_INITIALIZED, standbyState, TransactionIdIsNormal, and TransactionIdRetreat.

Referenced by StartupXLOG().

ProcArrayInstallImportedXmin()

bool ProcArrayInstallImportedXmin ( TransactionId  xmin, VirtualTransactionId *  sourcevxid  )

extern

Definition at line 2479 of file procarray.c.

{
    bool        result = false;
    ProcArrayStruct *arrayP = procArray;
    int         index;
 
    Assert(TransactionIdIsNormal(xmin));
    if (!sourcevxid)
        return false;
 
    /* Get lock so source xact can't end while we're doing this */
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    /*
     * Find the PGPROC entry of the source transaction. (This could use
     * GetPGProcByNumber(), unless it's a prepared xact.  But this isn't
     * performance critical.)
     */
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
        int         statusFlags = ProcGlobal->statusFlags[index];
        TransactionId xid;
 
        /* Ignore procs running LAZY VACUUM */
        if (statusFlags & PROC_IN_VACUUM)
            continue;
 
        /* We are only interested in the specific virtual transaction. */
        if (proc->vxid.procNumber != sourcevxid->procNumber)
            continue;
        if (proc->vxid.lxid != sourcevxid->localTransactionId)
            continue;
 
        /*
         * We check the transaction's database ID for paranoia's sake: if it's
         * in another DB then its xmin does not cover us.  Caller should have
         * detected this already, so we just treat any funny cases as
         * "transaction not found".
         */
        if (proc->databaseId != MyDatabaseId)
            continue;
 
        /*
         * Likewise, let's just make real sure its xmin does cover us.
         */
        xid = UINT32_ACCESS_ONCE(proc->xmin);
        if (!TransactionIdIsNormal(xid) ||
            !TransactionIdPrecedesOrEquals(xid, xmin))
            continue;
 
        /*
         * We're good.  Install the new xmin.  As in GetSnapshotData, set
         * TransactionXmin too.  (Note that because snapmgr.c called
         * GetSnapshotData first, we'll be overwriting a valid xmin here, so
         * we don't check that.)
         */
        MyProc->xmin = TransactionXmin = xmin;
 
        result = true;
        break;
    }
 
    LWLockRelease(ProcArrayLock);
 
    return result;
}

References allProcs, Assert, PGPROC::databaseId, VirtualTransactionId::localTransactionId, LW_SHARED, LWLockAcquire(), LWLockRelease(), PGPROC::lxid, MyDatabaseId, MyProc, ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PROC_IN_VACUUM, procArray, ProcGlobal, VirtualTransactionId::procNumber, PGPROC::procNumber, PROC_HDR::statusFlags, TransactionIdIsNormal, TransactionIdPrecedesOrEquals(), TransactionXmin, UINT32_ACCESS_ONCE, PGPROC::vxid, and PGPROC::xmin.

Referenced by GetSerializableTransactionSnapshotInt(), and SetTransactionSnapshot().

ProcArrayInstallRestoredXmin()

bool ProcArrayInstallRestoredXmin ( TransactionId  xmin, PGPROC *  proc  )

extern

Definition at line 2563 of file procarray.c.

{
    bool        result = false;
    TransactionId xid;
 
    Assert(TransactionIdIsNormal(xmin));
    Assert(proc != NULL);
 
    /*
     * Get an exclusive lock so that we can copy statusFlags from source proc.
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    /*
     * Be certain that the referenced PGPROC has an advertised xmin which is
     * no later than the one we're installing, so that the system-wide xmin
     * can't go backwards.  Also, make sure it's running in the same database,
     * so that the per-database xmin cannot go backwards.
     */
    xid = UINT32_ACCESS_ONCE(proc->xmin);
    if (proc->databaseId == MyDatabaseId &&
        TransactionIdIsNormal(xid) &&
        TransactionIdPrecedesOrEquals(xid, xmin))
    {
        /*
         * Install xmin and propagate the statusFlags that affect how the
         * value is interpreted by vacuum.
         */
        MyProc->xmin = TransactionXmin = xmin;
        MyProc->statusFlags = (MyProc->statusFlags & ~PROC_XMIN_FLAGS) |
            (proc->statusFlags & PROC_XMIN_FLAGS);
        ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
 
        result = true;
    }
 
    LWLockRelease(ProcArrayLock);
 
    return result;
}

References Assert, PGPROC::databaseId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MyDatabaseId, MyProc, PGPROC::pgxactoff, PROC_XMIN_FLAGS, ProcGlobal, PGPROC::statusFlags, PROC_HDR::statusFlags, TransactionIdIsNormal, TransactionIdPrecedesOrEquals(), TransactionXmin, UINT32_ACCESS_ONCE, and PGPROC::xmin.

Referenced by SetTransactionSnapshot().

ProcArrayRemove()

void ProcArrayRemove ( PGPROC *  proc, TransactionId  latestXid  )

extern

Definition at line 569 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         myoff;
    int         movecount;
 
#ifdef XIDCACHE_DEBUG
    /* dump stats at backend shutdown, but not prepared-xact end */
    if (proc->pid != 0)
        DisplayXidCache();
#endif
 
    /* See ProcGlobal comment explaining why both locks are held */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
    LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
 
    myoff = proc->pgxactoff;
 
    Assert(myoff >= 0 && myoff < arrayP->numProcs);
    Assert(ProcGlobal->allProcs[arrayP->pgprocnos[myoff]].pgxactoff == myoff);
 
    if (TransactionIdIsValid(latestXid))
    {
        Assert(TransactionIdIsValid(ProcGlobal->xids[myoff]));
 
        /* Advance global latestCompletedXid while holding the lock */
        MaintainLatestCompletedXid(latestXid);
 
        /* Same with xactCompletionCount  */
        TransamVariables->xactCompletionCount++;
 
        ProcGlobal->xids[myoff] = InvalidTransactionId;
        ProcGlobal->subxidStates[myoff].overflowed = false;
        ProcGlobal->subxidStates[myoff].count = 0;
    }
    else
    {
        /* Shouldn't be trying to remove a live transaction here */
        Assert(!TransactionIdIsValid(ProcGlobal->xids[myoff]));
    }
 
    Assert(!TransactionIdIsValid(ProcGlobal->xids[myoff]));
    Assert(ProcGlobal->subxidStates[myoff].count == 0);
    Assert(ProcGlobal->subxidStates[myoff].overflowed == false);
 
    ProcGlobal->statusFlags[myoff] = 0;
 
    /* Keep the PGPROC array sorted. See notes above */
    movecount = arrayP->numProcs - myoff - 1;
    memmove(&arrayP->pgprocnos[myoff],
            &arrayP->pgprocnos[myoff + 1],
            movecount * sizeof(*arrayP->pgprocnos));
    memmove(&ProcGlobal->xids[myoff],
            &ProcGlobal->xids[myoff + 1],
            movecount * sizeof(*ProcGlobal->xids));
    memmove(&ProcGlobal->subxidStates[myoff],
            &ProcGlobal->subxidStates[myoff + 1],
            movecount * sizeof(*ProcGlobal->subxidStates));
    memmove(&ProcGlobal->statusFlags[myoff],
            &ProcGlobal->statusFlags[myoff + 1],
            movecount * sizeof(*ProcGlobal->statusFlags));
 
    arrayP->pgprocnos[arrayP->numProcs - 1] = -1;   /* for debugging */
    arrayP->numProcs--;
 
    /*
     * Adjust pgxactoff of following procs for removed PGPROC (note that
     * numProcs already has been decremented).
     */
    for (int index = myoff; index < arrayP->numProcs; index++)
    {
        int         procno = arrayP->pgprocnos[index];
 
        Assert(procno >= 0 && procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS));
        Assert(allProcs[procno].pgxactoff - 1 == index);
 
        allProcs[procno].pgxactoff = index;
    }
 
    /*
     * Release in reversed acquisition order, to reduce frequency of having to
     * wait for XidGenLock while holding ProcArrayLock.
     */
    LWLockRelease(XidGenLock);
    LWLockRelease(ProcArrayLock);
}

References allProcs, PROC_HDR::allProcs, Assert, XidCacheStatus::count, InvalidTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaintainLatestCompletedXid(), ProcArrayStruct::maxProcs, NUM_AUXILIARY_PROCS, ProcArrayStruct::numProcs, XidCacheStatus::overflowed, ProcArrayStruct::pgprocnos, PGPROC::pgxactoff, PGPROC::pid, procArray, ProcGlobal, PROC_HDR::statusFlags, PROC_HDR::subxidStates, TransactionIdIsValid, TransamVariables, TransamVariablesData::xactCompletionCount, and PROC_HDR::xids.

Referenced by FinishPreparedTransaction(), and RemoveProcFromArray().

ProcArraySetReplicationSlotXmin()

void ProcArraySetReplicationSlotXmin ( TransactionId  xmin, TransactionId  catalog_xmin, bool  already_locked  )

extern

Definition at line 3950 of file procarray.c.

{
    Assert(!already_locked || LWLockHeldByMe(ProcArrayLock));
 
    if (!already_locked)
        LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    procArray->replication_slot_xmin = xmin;
    procArray->replication_slot_catalog_xmin = catalog_xmin;
 
    if (!already_locked)
        LWLockRelease(ProcArrayLock);
 
    elog(DEBUG1, "xmin required by slots: data %u, catalog %u",
         xmin, catalog_xmin);
}

References Assert, DEBUG1, elog, LW_EXCLUSIVE, LWLockAcquire(), LWLockHeldByMe(), LWLockRelease(), procArray, ProcArrayStruct::replication_slot_catalog_xmin, and ProcArrayStruct::replication_slot_xmin.

Referenced by ReplicationSlotsComputeRequiredXmin().

ProcArrayShmemInit()

void ProcArrayShmemInit ( void  )

extern

Definition at line 422 of file procarray.c.

{
    bool        found;
 
    /* Create or attach to the ProcArray shared structure */
    procArray = (ProcArrayStruct *)
        ShmemInitStruct("Proc Array",
                        add_size(offsetof(ProcArrayStruct, pgprocnos),
                                 mul_size(sizeof(int),
                                          PROCARRAY_MAXPROCS)),
                        &found);
 
    if (!found)
    {
        /*
         * We're the first - initialize.
         */
        procArray->numProcs = 0;
        procArray->maxProcs = PROCARRAY_MAXPROCS;
        procArray->maxKnownAssignedXids = TOTAL_MAX_CACHED_SUBXIDS;
        procArray->numKnownAssignedXids = 0;
        procArray->tailKnownAssignedXids = 0;
        procArray->headKnownAssignedXids = 0;
        procArray->lastOverflowedXid = InvalidTransactionId;
        procArray->replication_slot_xmin = InvalidTransactionId;
        procArray->replication_slot_catalog_xmin = InvalidTransactionId;
        TransamVariables->xactCompletionCount = 1;
    }
 
    allProcs = ProcGlobal->allProcs;
 
    /* Create or attach to the KnownAssignedXids arrays too, if needed */
    if (EnableHotStandby)
    {
        KnownAssignedXids = (TransactionId *)
            ShmemInitStruct("KnownAssignedXids",
                            mul_size(sizeof(TransactionId),
                                     TOTAL_MAX_CACHED_SUBXIDS),
                            &found);
        KnownAssignedXidsValid = (bool *)
            ShmemInitStruct("KnownAssignedXidsValid",
                            mul_size(sizeof(bool), TOTAL_MAX_CACHED_SUBXIDS),
                            &found);
    }
}

References add_size(), allProcs, PROC_HDR::allProcs, EnableHotStandby, ProcArrayStruct::headKnownAssignedXids, InvalidTransactionId, KnownAssignedXids, KnownAssignedXidsValid, ProcArrayStruct::lastOverflowedXid, ProcArrayStruct::maxKnownAssignedXids, ProcArrayStruct::maxProcs, mul_size(), ProcArrayStruct::numKnownAssignedXids, ProcArrayStruct::numProcs, procArray, PROCARRAY_MAXPROCS, ProcGlobal, ProcArrayStruct::replication_slot_catalog_xmin, ProcArrayStruct::replication_slot_xmin, ShmemInitStruct(), ProcArrayStruct::tailKnownAssignedXids, TOTAL_MAX_CACHED_SUBXIDS, TransamVariables, and TransamVariablesData::xactCompletionCount.

Referenced by CreateOrAttachShmemStructs().

ProcArrayShmemSize()

Size ProcArrayShmemSize ( void  )

extern

Definition at line 380 of file procarray.c.

{
    Size        size;
 
    /* Size of the ProcArray structure itself */
#define PROCARRAY_MAXPROCS  (MaxBackends + max_prepared_xacts)
 
    size = offsetof(ProcArrayStruct, pgprocnos);
    size = add_size(size, mul_size(sizeof(int), PROCARRAY_MAXPROCS));
 
    /*
     * During Hot Standby processing we have a data structure called
     * KnownAssignedXids, created in shared memory. Local data structures are
     * also created in various backends during GetSnapshotData(),
     * TransactionIdIsInProgress() and GetRunningTransactionData(). All of the
     * main structures created in those functions must be identically sized,
     * since we may at times copy the whole of the data structures around. We
     * refer to this size as TOTAL_MAX_CACHED_SUBXIDS.
     *
     * Ideally we'd only create this structure if we were actually doing hot
     * standby in the current run, but we don't know that yet at the time
     * shared memory is being set up.
     */
#define TOTAL_MAX_CACHED_SUBXIDS \
    ((PGPROC_MAX_CACHED_SUBXIDS + 1) * PROCARRAY_MAXPROCS)
 
    if (EnableHotStandby)
    {
        size = add_size(size,
                        mul_size(sizeof(TransactionId),
                                 TOTAL_MAX_CACHED_SUBXIDS));
        size = add_size(size,
                        mul_size(sizeof(bool), TOTAL_MAX_CACHED_SUBXIDS));
    }
 
    return size;
}

References add_size(), EnableHotStandby, mul_size(), PROCARRAY_MAXPROCS, and TOTAL_MAX_CACHED_SUBXIDS.

Referenced by CalculateShmemSize().

ProcNumberGetProc()

PGPROC * ProcNumberGetProc ( int  procNumber )

extern

Definition at line 3098 of file procarray.c.

{
    PGPROC     *result;
 
    if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
        return NULL;
    result = GetPGProcByNumber(procNumber);
 
    if (result->pid == 0)
        return NULL;
 
    return result;
}

References PROC_HDR::allProcCount, GetPGProcByNumber, PGPROC::pid, and ProcGlobal.

Referenced by checkTempNamespaceStatus(), LogRecoveryConflict(), VirtualXactLock(), WaitForLockersMultiple(), and WaitForOlderSnapshots().

ProcNumberGetTransactionIds()

void ProcNumberGetTransactionIds ( int  procNumber, TransactionId *  xid, TransactionId *  xmin, int *  nsubxid, bool *  overflowed  )

extern

Definition at line 3120 of file procarray.c.

{
    PGPROC     *proc;
 
    *xid = InvalidTransactionId;
    *xmin = InvalidTransactionId;
    *nsubxid = 0;
    *overflowed = false;
 
    if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
        return;
    proc = GetPGProcByNumber(procNumber);
 
    /* Need to lock out additions/removals of backends */
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    if (proc->pid != 0)
    {
        *xid = proc->xid;
        *xmin = proc->xmin;
        *nsubxid = proc->subxidStatus.count;
        *overflowed = proc->subxidStatus.overflowed;
    }
 
    LWLockRelease(ProcArrayLock);
}

References PROC_HDR::allProcCount, XidCacheStatus::count, GetPGProcByNumber, InvalidTransactionId, LW_SHARED, LWLockAcquire(), LWLockRelease(), XidCacheStatus::overflowed, PGPROC::pid, ProcGlobal, PGPROC::subxidStatus, PGPROC::xid, and PGPROC::xmin.

Referenced by pgstat_read_current_status().

RecordKnownAssignedTransactionIds()

void RecordKnownAssignedTransactionIds ( TransactionId  xid )

extern

Definition at line 4410 of file procarray.c.

{
    Assert(standbyState >= STANDBY_INITIALIZED);
    Assert(TransactionIdIsValid(xid));
    Assert(TransactionIdIsValid(latestObservedXid));
 
    elog(DEBUG4, "record known xact %u latestObservedXid %u",
         xid, latestObservedXid);
 
    /*
     * When a newly observed xid arrives, it is frequently the case that it is
     * *not* the next xid in sequence. When this occurs, we must treat the
     * intervening xids as running also.
     */
    if (TransactionIdFollows(xid, latestObservedXid))
    {
        TransactionId next_expected_xid;
 
        /*
         * Extend subtrans like we do in GetNewTransactionId() during normal
         * operation using individual extend steps. Note that we do not need
         * to extend clog since its extensions are WAL logged.
         *
         * This part has to be done regardless of standbyState since we
         * immediately start assigning subtransactions to their toplevel
         * transactions.
         */
        next_expected_xid = latestObservedXid;
        while (TransactionIdPrecedes(next_expected_xid, xid))
        {
            TransactionIdAdvance(next_expected_xid);
            ExtendSUBTRANS(next_expected_xid);
        }
        Assert(next_expected_xid == xid);
 
        /*
         * If the KnownAssignedXids machinery isn't up yet, there's nothing
         * more to do since we don't track assigned xids yet.
         */
        if (standbyState <= STANDBY_INITIALIZED)
        {
            latestObservedXid = xid;
            return;
        }
 
        /*
         * Add (latestObservedXid, xid] onto the KnownAssignedXids array.
         */
        next_expected_xid = latestObservedXid;
        TransactionIdAdvance(next_expected_xid);
        KnownAssignedXidsAdd(next_expected_xid, xid, false);
 
        /*
         * Now we can advance latestObservedXid
         */
        latestObservedXid = xid;
 
        /* TransamVariables->nextXid must be beyond any observed xid */
        AdvanceNextFullTransactionIdPastXid(latestObservedXid);
    }
}

References AdvanceNextFullTransactionIdPastXid(), Assert, DEBUG4, elog, ExtendSUBTRANS(), KnownAssignedXidsAdd(), latestObservedXid, STANDBY_INITIALIZED, standbyState, TransactionIdAdvance, TransactionIdFollows(), TransactionIdIsValid, and TransactionIdPrecedes().

Referenced by ApplyWalRecord(), ProcArrayApplyXidAssignment(), xact_redo_abort(), and xact_redo_commit().

SignalRecoveryConflict()

bool SignalRecoveryConflict ( PGPROC *  proc, pid_t  pid, RecoveryConflictReason  reason  )

extern

Definition at line 3454 of file procarray.c.

{
    bool        found = false;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    /*
     * Kill the pid if it's still here. If not, that's what we wanted so
     * ignore any errors.
     */
    if (proc->pid == pid)
    {
        (void) pg_atomic_fetch_or_u32(&proc->pendingRecoveryConflicts, (1 << reason));
 
        /* wake up the process */
        (void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT, GetNumberFromPGProc(proc));
        found = true;
    }
 
    LWLockRelease(ProcArrayLock);
 
    return found;
}

References GetNumberFromPGProc, LW_SHARED, LWLockAcquire(), LWLockRelease(), PGPROC::pendingRecoveryConflicts, pg_atomic_fetch_or_u32(), PGPROC::pid, PROCSIG_RECOVERY_CONFLICT, and SendProcSignal().

Referenced by InvalidatePossiblyObsoleteSlot().

SignalRecoveryConflictWithDatabase()

void SignalRecoveryConflictWithDatabase ( Oid  databaseid, RecoveryConflictReason  reason  )

extern

Definition at line 3529 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         index;
 
    /* tell all backends to die */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
 
        if (databaseid == InvalidOid || proc->databaseId == databaseid)
        {
            VirtualTransactionId procvxid;
            pid_t       pid;
 
            GET_VXID_FROM_PGPROC(procvxid, *proc);
 
            pid = proc->pid;
            if (pid != 0)
            {
                (void) pg_atomic_fetch_or_u32(&proc->pendingRecoveryConflicts, (1 << reason));
 
                /*
                 * Kill the pid if it's still here. If not, that's what we
                 * wanted so ignore any errors.
                 */
                (void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT, procvxid.procNumber);
            }
        }
    }
 
    LWLockRelease(ProcArrayLock);
}

References allProcs, PGPROC::databaseId, GET_VXID_FROM_PGPROC, InvalidOid, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, PGPROC::pendingRecoveryConflicts, pg_atomic_fetch_or_u32(), ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, VirtualTransactionId::procNumber, PROCSIG_RECOVERY_CONFLICT, and SendProcSignal().

Referenced by ResolveRecoveryConflictWithDatabase(), and SendRecoveryConflictWithBufferPin().

SignalRecoveryConflictWithVirtualXID()

bool SignalRecoveryConflictWithVirtualXID ( VirtualTransactionId  vxid, RecoveryConflictReason  reason  )

extern

Definition at line 3484 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    int         index;
    pid_t       pid = 0;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (index = 0; index < arrayP->numProcs; index++)
    {
        int         pgprocno = arrayP->pgprocnos[index];
        PGPROC     *proc = &allProcs[pgprocno];
        VirtualTransactionId procvxid;
 
        GET_VXID_FROM_PGPROC(procvxid, *proc);
 
        if (procvxid.procNumber == vxid.procNumber &&
            procvxid.localTransactionId == vxid.localTransactionId)
        {
            pid = proc->pid;
            if (pid != 0)
            {
                (void) pg_atomic_fetch_or_u32(&proc->pendingRecoveryConflicts, (1 << reason));
 
                /*
                 * Kill the pid if it's still here. If not, that's what we
                 * wanted so ignore any errors.
                 */
                (void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT, vxid.procNumber);
            }
            break;
        }
    }
 
    LWLockRelease(ProcArrayLock);
 
    return pid != 0;
}

References allProcs, GET_VXID_FROM_PGPROC, VirtualTransactionId::localTransactionId, LW_SHARED, LWLockAcquire(), LWLockRelease(), ProcArrayStruct::numProcs, PGPROC::pendingRecoveryConflicts, pg_atomic_fetch_or_u32(), ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, VirtualTransactionId::procNumber, PROCSIG_RECOVERY_CONFLICT, and SendProcSignal().

Referenced by ResolveRecoveryConflictWithLock(), and ResolveRecoveryConflictWithVirtualXIDs().

TerminateOtherDBBackends()

void TerminateOtherDBBackends ( Oid  databaseId )

extern

Definition at line 3835 of file procarray.c.

{
    ProcArrayStruct *arrayP = procArray;
    List       *pids = NIL;
    int         nprepared = 0;
    int         i;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    for (i = 0; i < procArray->numProcs; i++)
    {
        int         pgprocno = arrayP->pgprocnos[i];
        PGPROC     *proc = &allProcs[pgprocno];
 
        if (proc->databaseId != databaseId)
            continue;
        if (proc == MyProc)
            continue;
 
        if (proc->pid != 0)
            pids = lappend_int(pids, proc->pid);
        else
            nprepared++;
    }
 
    LWLockRelease(ProcArrayLock);
 
    if (nprepared > 0)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_IN_USE),
                 errmsg("database \"%s\" is being used by prepared transactions",
                        get_database_name(databaseId)),
                 errdetail_plural("There is %d prepared transaction using the database.",
                                  "There are %d prepared transactions using the database.",
                                  nprepared,
                                  nprepared)));
 
    if (pids)
    {
        ListCell   *lc;
 
        /*
         * Permissions checks relax the pg_terminate_backend checks in two
         * ways, both by omitting the !OidIsValid(proc->roleId) check:
         *
         * - Accept terminating autovacuum workers, since DROP DATABASE
         * without FORCE terminates them.
         *
         * - Accept terminating bgworkers.  For bgworker authors, it's
         * convenient to be able to recommend FORCE if a worker is blocking
         * DROP DATABASE unexpectedly.
         *
         * Unlike pg_terminate_backend, we don't raise some warnings - like
         * "PID %d is not a PostgreSQL server process", because for us already
         * finished session is not a problem.
         */
        foreach(lc, pids)
        {
            int         pid = lfirst_int(lc);
            PGPROC     *proc = BackendPidGetProc(pid);
 
            if (proc != NULL)
            {
                if (superuser_arg(proc->roleId) && !superuser())
                    ereport(ERROR,
                            (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                             errmsg("permission denied to terminate process"),
                             errdetail("Only roles with the %s attribute may terminate processes of roles with the %s attribute.",
                                       "SUPERUSER", "SUPERUSER")));
 
                if (!has_privs_of_role(GetUserId(), proc->roleId) &&
                    !has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_BACKEND))
                    ereport(ERROR,
                            (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                             errmsg("permission denied to terminate process"),
                             errdetail("Only roles with privileges of the role whose process is being terminated or with privileges of the \"%s\" role may terminate this process.",
                                       "pg_signal_backend")));
            }
        }
 
        /*
         * There's a race condition here: once we release the ProcArrayLock,
         * it's possible for the session to exit before we issue kill.  That
         * race condition possibility seems too unlikely to worry about.  See
         * pg_signal_backend.
         */
        foreach(lc, pids)
        {
            int         pid = lfirst_int(lc);
            PGPROC     *proc = BackendPidGetProc(pid);
 
            if (proc != NULL)
            {
                /*
                 * If we have setsid(), signal the backend's whole process
                 * group
                 */
#ifdef HAVE_SETSID
                (void) kill(-pid, SIGTERM);
#else
                (void) kill(pid, SIGTERM);
#endif
            }
        }
    }
}

References allProcs, BackendPidGetProc(), PGPROC::databaseId, ereport, errcode(), errdetail(), errdetail_plural(), errmsg, ERROR, get_database_name(), GetUserId(), has_privs_of_role(), i, kill, lappend_int(), lfirst_int, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyProc, NIL, ProcArrayStruct::numProcs, ProcArrayStruct::pgprocnos, PGPROC::pid, procArray, PGPROC::roleId, superuser(), and superuser_arg().

Referenced by dropdb().

TransactionIdIsInProgress()

bool TransactionIdIsInProgress ( TransactionId  xid )

extern

Definition at line 1401 of file procarray.c.

{
    static TransactionId *xids = NULL;
    static TransactionId *other_xids;
    XidCacheStatus *other_subxidstates;
    int         nxids = 0;
    ProcArrayStruct *arrayP = procArray;
    TransactionId topxid;
    TransactionId latestCompletedXid;
    int         mypgxactoff;
    int         numProcs;
    int         j;
 
    /*
     * Don't bother checking a transaction older than RecentXmin; it could not
     * possibly still be running.  (Note: in particular, this guarantees that
     * we reject InvalidTransactionId, FrozenTransactionId, etc as not
     * running.)
     */
    if (TransactionIdPrecedes(xid, RecentXmin))
    {
        xc_by_recent_xmin_inc();
        return false;
    }
 
    /*
     * We may have just checked the status of this transaction, so if it is
     * already known to be completed, we can fall out without any access to
     * shared memory.
     */
    if (TransactionIdEquals(cachedXidIsNotInProgress, xid))
    {
        xc_by_known_xact_inc();
        return false;
    }
 
    /*
     * Also, we can handle our own transaction (and subtransactions) without
     * any access to shared memory.
     */
    if (TransactionIdIsCurrentTransactionId(xid))
    {
        xc_by_my_xact_inc();
        return true;
    }
 
    /*
     * If first time through, get workspace to remember main XIDs in. We
     * malloc it permanently to avoid repeated palloc/pfree overhead.
     */
    if (xids == NULL)
    {
        /*
         * In hot standby mode, reserve enough space to hold all xids in the
         * known-assigned list. If we later finish recovery, we no longer need
         * the bigger array, but we don't bother to shrink it.
         */
        int         maxxids = RecoveryInProgress() ? TOTAL_MAX_CACHED_SUBXIDS : arrayP->maxProcs;
 
        xids = (TransactionId *) malloc(maxxids * sizeof(TransactionId));
        if (xids == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
    }
 
    other_xids = ProcGlobal->xids;
    other_subxidstates = ProcGlobal->subxidStates;
 
    LWLockAcquire(ProcArrayLock, LW_SHARED);
 
    /*
     * Now that we have the lock, we can check latestCompletedXid; if the
     * target Xid is after that, it's surely still running.
     */
    latestCompletedXid =
        XidFromFullTransactionId(TransamVariables->latestCompletedXid);
    if (TransactionIdPrecedes(latestCompletedXid, xid))
    {
        LWLockRelease(ProcArrayLock);
        xc_by_latest_xid_inc();
        return true;
    }
 
    /* No shortcuts, gotta grovel through the array */
    mypgxactoff = MyProc->pgxactoff;
    numProcs = arrayP->numProcs;
    for (int pgxactoff = 0; pgxactoff < numProcs; pgxactoff++)
    {
        int         pgprocno;
        PGPROC     *proc;
        TransactionId pxid;
        int         pxids;
 
        /* Ignore ourselves --- dealt with it above */
        if (pgxactoff == mypgxactoff)
            continue;
 
        /* Fetch xid just once - see GetNewTransactionId */
        pxid = UINT32_ACCESS_ONCE(other_xids[pgxactoff]);
 
        if (!TransactionIdIsValid(pxid))
            continue;
 
        /*
         * Step 1: check the main Xid
         */
        if (TransactionIdEquals(pxid, xid))
        {
            LWLockRelease(ProcArrayLock);
            xc_by_main_xid_inc();
            return true;
        }
 
        /*
         * We can ignore main Xids that are younger than the target Xid, since
         * the target could not possibly be their child.
         */
        if (TransactionIdPrecedes(xid, pxid))
            continue;
 
        /*
         * Step 2: check the cached child-Xids arrays
         */
        pxids = other_subxidstates[pgxactoff].count;
        pg_read_barrier();      /* pairs with barrier in GetNewTransactionId() */
        pgprocno = arrayP->pgprocnos[pgxactoff];
        proc = &allProcs[pgprocno];
        for (j = pxids - 1; j >= 0; j--)
        {
            /* Fetch xid just once - see GetNewTransactionId */
            TransactionId cxid = UINT32_ACCESS_ONCE(proc->subxids.xids[j]);
 
            if (TransactionIdEquals(cxid, xid))
            {
                LWLockRelease(ProcArrayLock);
                xc_by_child_xid_inc();
                return true;
            }
        }
 
        /*
         * Save the main Xid for step 4.  We only need to remember main Xids
         * that have uncached children.  (Note: there is no race condition
         * here because the overflowed flag cannot be cleared, only set, while
         * we hold ProcArrayLock.  So we can't miss an Xid that we need to
         * worry about.)
         */
        if (other_subxidstates[pgxactoff].overflowed)
            xids[nxids++] = pxid;
    }
 
    /*
     * Step 3: in hot standby mode, check the known-assigned-xids list.  XIDs
     * in the list must be treated as running.
     */
    if (RecoveryInProgress())
    {
        /* none of the PGPROC entries should have XIDs in hot standby mode */
        Assert(nxids == 0);
 
        if (KnownAssignedXidExists(xid))
        {
            LWLockRelease(ProcArrayLock);
            xc_by_known_assigned_inc();
            return true;
        }
 
        /*
         * If the KnownAssignedXids overflowed, we have to check pg_subtrans
         * too.  Fetch all xids from KnownAssignedXids that are lower than
         * xid, since if xid is a subtransaction its parent will always have a
         * lower value.  Note we will collect both main and subXIDs here, but
         * there's no help for it.
         */
        if (TransactionIdPrecedesOrEquals(xid, procArray->lastOverflowedXid))
            nxids = KnownAssignedXidsGet(xids, xid);
    }
 
    LWLockRelease(ProcArrayLock);
 
    /*
     * If none of the relevant caches overflowed, we know the Xid is not
     * running without even looking at pg_subtrans.
     */
    if (nxids == 0)
    {
        xc_no_overflow_inc();
        cachedXidIsNotInProgress = xid;
        return false;
    }
 
    /*
     * Step 4: have to check pg_subtrans.
     *
     * At this point, we know it's either a subtransaction of one of the Xids
     * in xids[], or it's not running.  If it's an already-failed
     * subtransaction, we want to say "not running" even though its parent may
     * still be running.  So first, check pg_xact to see if it's been aborted.
     */
    xc_slow_answer_inc();
 
    if (TransactionIdDidAbort(xid))
    {
        cachedXidIsNotInProgress = xid;
        return false;
    }
 
    /*
     * It isn't aborted, so check whether the transaction tree it belongs to
     * is still running (or, more precisely, whether it was running when we
     * held ProcArrayLock).
     */
    topxid = SubTransGetTopmostTransaction(xid);
    Assert(TransactionIdIsValid(topxid));
    if (!TransactionIdEquals(topxid, xid) &&
        pg_lfind32(topxid, xids, nxids))
        return true;
 
    cachedXidIsNotInProgress = xid;
    return false;
}

References allProcs, Assert, cachedXidIsNotInProgress, XidCacheStatus::count, ereport, errcode(), errmsg, ERROR, j, KnownAssignedXidExists(), KnownAssignedXidsGet(), ProcArrayStruct::lastOverflowedXid, TransamVariablesData::latestCompletedXid, LW_SHARED, LWLockAcquire(), LWLockRelease(), malloc, ProcArrayStruct::maxProcs, MyProc, ProcArrayStruct::numProcs, pg_lfind32(), pg_read_barrier, ProcArrayStruct::pgprocnos, PGPROC::pgxactoff, procArray, ProcGlobal, RecentXmin, RecoveryInProgress(), SubTransGetTopmostTransaction(), PGPROC::subxids, PROC_HDR::subxidStates, TOTAL_MAX_CACHED_SUBXIDS, TransactionIdDidAbort(), TransactionIdEquals, TransactionIdIsCurrentTransactionId(), TransactionIdIsValid, TransactionIdPrecedes(), TransactionIdPrecedesOrEquals(), TransamVariables, UINT32_ACCESS_ONCE, xc_by_child_xid_inc, xc_by_known_assigned_inc, xc_by_known_xact_inc, xc_by_latest_xid_inc, xc_by_main_xid_inc, xc_by_my_xact_inc, xc_by_recent_xmin_inc, xc_no_overflow_inc, xc_slow_answer_inc, XidFromFullTransactionId, XidCache::xids, and PROC_HDR::xids.

Referenced by check_safe_enum_use(), compute_new_xmax_infomask(), ConditionalXactLockTableWait(), Do_MultiXactIdWait(), DoesMultiXactIdConflict(), FreezeMultiXactId(), get_xid_status(), HandleConcurrentAbort(), HeapTupleCleanMoved(), HeapTupleHeaderIsOnlyLocked(), HeapTupleSatisfiesDirty(), HeapTupleSatisfiesSelf(), HeapTupleSatisfiesUpdate(), HeapTupleSatisfiesVacuumHorizon(), MultiXactIdExpand(), MultiXactIdIsRunning(), pg_xact_status(), ReorderBufferCheckAndTruncateAbortedTXN(), test_lockmode_for_conflict(), verify_heapam(), and XactLockTableWait().

XidCacheRemoveRunningXids()

void XidCacheRemoveRunningXids ( TransactionId  xid, int  nxids, const TransactionId *  xids, TransactionId  latestXid  )

extern

Definition at line 3998 of file procarray.c.

{
    int         i,
                j;
    XidCacheStatus *mysubxidstat;
 
    Assert(TransactionIdIsValid(xid));
 
    /*
     * We must hold ProcArrayLock exclusively in order to remove transactions
     * from the PGPROC array.  (See src/backend/access/transam/README.)  It's
     * possible this could be relaxed since we know this routine is only used
     * to abort subtransactions, but pending closer analysis we'd best be
     * conservative.
     *
     * Note that we do not have to be careful about memory ordering of our own
     * reads wrt. GetNewTransactionId() here - only this process can modify
     * relevant fields of MyProc/ProcGlobal->xids[].  But we do have to be
     * careful about our own writes being well ordered.
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
    mysubxidstat = &ProcGlobal->subxidStates[MyProc->pgxactoff];
 
    /*
     * Under normal circumstances xid and xids[] will be in increasing order,
     * as will be the entries in subxids.  Scan backwards to avoid O(N^2)
     * behavior when removing a lot of xids.
     */
    for (i = nxids - 1; i >= 0; i--)
    {
        TransactionId anxid = xids[i];
 
        for (j = MyProc->subxidStatus.count - 1; j >= 0; j--)
        {
            if (TransactionIdEquals(MyProc->subxids.xids[j], anxid))
            {
                MyProc->subxids.xids[j] = MyProc->subxids.xids[MyProc->subxidStatus.count - 1];
                pg_write_barrier();
                mysubxidstat->count--;
                MyProc->subxidStatus.count--;
                break;
            }
        }
 
        /*
         * Ordinarily we should have found it, unless the cache has
         * overflowed. However it's also possible for this routine to be
         * invoked multiple times for the same subtransaction, in case of an
         * error during AbortSubTransaction.  So instead of Assert, emit a
         * debug warning.
         */
        if (j < 0 && !MyProc->subxidStatus.overflowed)
            elog(WARNING, "did not find subXID %u in MyProc", anxid);
    }
 
    for (j = MyProc->subxidStatus.count - 1; j >= 0; j--)
    {
        if (TransactionIdEquals(MyProc->subxids.xids[j], xid))
        {
            MyProc->subxids.xids[j] = MyProc->subxids.xids[MyProc->subxidStatus.count - 1];
            pg_write_barrier();
            mysubxidstat->count--;
            MyProc->subxidStatus.count--;
            break;
        }
    }
    /* Ordinarily we should have found it, unless the cache has overflowed */
    if (j < 0 && !MyProc->subxidStatus.overflowed)
        elog(WARNING, "did not find subXID %u in MyProc", xid);
 
    /* Also advance global latestCompletedXid while holding the lock */
    MaintainLatestCompletedXid(latestXid);
 
    /* ... and xactCompletionCount */
    TransamVariables->xactCompletionCount++;
 
    LWLockRelease(ProcArrayLock);
}

References Assert, XidCacheStatus::count, elog, i, j, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaintainLatestCompletedXid(), MyProc, pg_write_barrier, PGPROC::pgxactoff, ProcGlobal, PGPROC::subxids, PROC_HDR::subxidStates, PGPROC::subxidStatus, TransactionIdEquals, TransactionIdIsValid, TransamVariables, WARNING, TransamVariablesData::xactCompletionCount, and XidCache::xids.

Referenced by RecordTransactionAbort().