subtrans.h File Reference

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Functions
void	SubTransSetParent (TransactionId xid, TransactionId parent)
TransactionId	SubTransGetParent (TransactionId xid)
TransactionId	SubTransGetTopmostTransaction (TransactionId xid)
void	BootStrapSUBTRANS (void)
void	StartupSUBTRANS (TransactionId oldestActiveXID)
void	CheckPointSUBTRANS (void)
void	ExtendSUBTRANS (TransactionId newestXact)
void	TruncateSUBTRANS (TransactionId oldestXact)

Function Documentation

BootStrapSUBTRANS()

void BootStrapSUBTRANS ( void  )

extern

Definition at line 288 of file subtrans.c.

{
    /* Zero the initial page and flush it to disk */
    SimpleLruZeroAndWritePage(SubTransCtl, 0);
}

References SimpleLruZeroAndWritePage(), and SubTransCtl.

Referenced by BootStrapXLOG().

CheckPointSUBTRANS()

void CheckPointSUBTRANS ( void  )

extern

Definition at line 348 of file subtrans.c.

{
    /*
     * Write dirty SUBTRANS pages to disk
     *
     * This is not actually necessary from a correctness point of view. We do
     * it merely to improve the odds that writing of dirty pages is done by
     * the checkpoint process and not by backends.
     */
    TRACE_POSTGRESQL_SUBTRANS_CHECKPOINT_START(true);
    SimpleLruWriteAll(SubTransCtl, true);
    TRACE_POSTGRESQL_SUBTRANS_CHECKPOINT_DONE(true);
}

References fb(), SimpleLruWriteAll(), and SubTransCtl.

Referenced by CheckPointGuts().

ExtendSUBTRANS()

void ExtendSUBTRANS ( TransactionId  newestXact )

extern

Definition at line 372 of file subtrans.c.

{
    int64       pageno;
    LWLock     *lock;
 
    /*
     * No work except at first XID of a page.  But beware: just after
     * wraparound, the first XID of page zero is FirstNormalTransactionId.
     */
    if (TransactionIdToEntry(newestXact) != 0 &&
        !TransactionIdEquals(newestXact, FirstNormalTransactionId))
        return;
 
    pageno = TransactionIdToPage(newestXact);
 
    lock = SimpleLruGetBankLock(SubTransCtl, pageno);
    LWLockAcquire(lock, LW_EXCLUSIVE);
 
    /* Zero the page */
    SimpleLruZeroPage(SubTransCtl, pageno);
 
    LWLockRelease(lock);
}

References fb(), FirstNormalTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), SimpleLruGetBankLock(), SimpleLruZeroPage(), SubTransCtl, TransactionIdEquals, TransactionIdToEntry, and TransactionIdToPage().

Referenced by GetNewTransactionId(), ProcArrayApplyRecoveryInfo(), and RecordKnownAssignedTransactionIds().

StartupSUBTRANS()

void StartupSUBTRANS ( TransactionId  oldestActiveXID )

extern

Definition at line 302 of file subtrans.c.

{
    FullTransactionId nextXid;
    int64       startPage;
    int64       endPage;
    LWLock     *prevlock = NULL;
    LWLock     *lock;
 
    /*
     * Since we don't expect pg_subtrans to be valid across crashes, we
     * initialize the currently-active page(s) to zeroes during startup.
     * Whenever we advance into a new page, ExtendSUBTRANS will likewise zero
     * the new page without regard to whatever was previously on disk.
     */
    startPage = TransactionIdToPage(oldestActiveXID);
    nextXid = TransamVariables->nextXid;
    endPage = TransactionIdToPage(XidFromFullTransactionId(nextXid));
 
    for (;;)
    {
        lock = SimpleLruGetBankLock(SubTransCtl, startPage);
        if (prevlock != lock)
        {
            if (prevlock)
                LWLockRelease(prevlock);
            LWLockAcquire(lock, LW_EXCLUSIVE);
            prevlock = lock;
        }
 
        (void) SimpleLruZeroPage(SubTransCtl, startPage);
        if (startPage == endPage)
            break;
 
        startPage++;
        /* must account for wraparound */
        if (startPage > TransactionIdToPage(MaxTransactionId))
            startPage = 0;
    }
 
    LWLockRelease(lock);
}

References fb(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaxTransactionId, TransamVariablesData::nextXid, SimpleLruGetBankLock(), SimpleLruZeroPage(), SubTransCtl, TransactionIdToPage(), TransamVariables, and XidFromFullTransactionId.

Referenced by StartupXLOG().

SubTransGetParent()

TransactionId SubTransGetParent ( TransactionId  xid )

extern

Definition at line 129 of file subtrans.c.

{
    int64       pageno = TransactionIdToPage(xid);
    int         entryno = TransactionIdToEntry(xid);
    int         slotno;
    TransactionId *ptr;
    TransactionId parent;
 
    /* Can't ask about stuff that might not be around anymore */
    Assert(TransactionIdFollowsOrEquals(xid, TransactionXmin));
 
    /* Bootstrap and frozen XIDs have no parent */
    if (!TransactionIdIsNormal(xid))
        return InvalidTransactionId;
 
    /* lock is acquired by SimpleLruReadPage_ReadOnly */
 
    slotno = SimpleLruReadPage_ReadOnly(SubTransCtl, pageno, &xid);
    ptr = (TransactionId *) SubTransCtl->shared->page_buffer[slotno];
    ptr += entryno;
 
    parent = *ptr;
 
    LWLockRelease(SimpleLruGetBankLock(SubTransCtl, pageno));
 
    return parent;
}

References Assert, fb(), InvalidTransactionId, LWLockRelease(), SimpleLruGetBankLock(), SimpleLruReadPage_ReadOnly(), SubTransCtl, TransactionIdFollowsOrEquals(), TransactionIdIsNormal, TransactionIdToEntry, TransactionIdToPage(), and TransactionXmin.

Referenced by SubTransGetTopmostTransaction(), TransactionIdDidAbort(), and TransactionIdDidCommit().

SubTransGetTopmostTransaction()

TransactionId SubTransGetTopmostTransaction ( TransactionId  xid )

extern

Definition at line 170 of file subtrans.c.

{
    TransactionId parentXid = xid,
                previousXid = xid;
 
    /* Can't ask about stuff that might not be around anymore */
    Assert(TransactionIdFollowsOrEquals(xid, TransactionXmin));
 
    while (TransactionIdIsValid(parentXid))
    {
        previousXid = parentXid;
        if (TransactionIdPrecedes(parentXid, TransactionXmin))
            break;
        parentXid = SubTransGetParent(parentXid);
 
        /*
         * By convention the parent xid gets allocated first, so should always
         * precede the child xid. Anything else points to a corrupted data
         * structure that could lead to an infinite loop, so exit.
         */
        if (!TransactionIdPrecedes(parentXid, previousXid))
            elog(ERROR, "pg_subtrans contains invalid entry: xid %u points to parent xid %u",
                 previousXid, parentXid);
    }
 
    Assert(TransactionIdIsValid(previousXid));
 
    return previousXid;
}

References Assert, elog, ERROR, fb(), SubTransGetParent(), TransactionIdFollowsOrEquals(), TransactionIdIsValid, TransactionIdPrecedes(), and TransactionXmin.

Referenced by ConditionalXactLockTableWait(), HeapCheckForSerializableConflictOut(), TransactionIdIsInProgress(), XactLockTableWait(), and XidInMVCCSnapshot().

SubTransSetParent()

void SubTransSetParent ( TransactionId  xid, TransactionId  parent  )

extern

Definition at line 92 of file subtrans.c.

{
    int64       pageno = TransactionIdToPage(xid);
    int         entryno = TransactionIdToEntry(xid);
    int         slotno;
    LWLock     *lock;
    TransactionId *ptr;
 
    Assert(TransactionIdIsValid(parent));
    Assert(TransactionIdFollows(xid, parent));
 
    lock = SimpleLruGetBankLock(SubTransCtl, pageno);
    LWLockAcquire(lock, LW_EXCLUSIVE);
 
    slotno = SimpleLruReadPage(SubTransCtl, pageno, true, &xid);
    ptr = (TransactionId *) SubTransCtl->shared->page_buffer[slotno];
    ptr += entryno;
 
    /*
     * It's possible we'll try to set the parent xid multiple times but we
     * shouldn't ever be changing the xid from one valid xid to another valid
     * xid, which would corrupt the data structure.
     */
    if (*ptr != parent)
    {
        Assert(*ptr == InvalidTransactionId);
        *ptr = parent;
        SubTransCtl->shared->page_dirty[slotno] = true;
    }
 
    LWLockRelease(lock);
}

References Assert, fb(), InvalidTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), SimpleLruGetBankLock(), SimpleLruReadPage(), SubTransCtl, TransactionIdFollows(), TransactionIdIsValid, TransactionIdToEntry, and TransactionIdToPage().

Referenced by AssignTransactionId(), ProcArrayApplyXidAssignment(), and ProcessTwoPhaseBuffer().

TruncateSUBTRANS()

void TruncateSUBTRANS ( TransactionId  oldestXact )

extern

Definition at line 404 of file subtrans.c.

{
    int64       cutoffPage;
 
    /*
     * The cutoff point is the start of the segment containing oldestXact. We
     * pass the *page* containing oldestXact to SimpleLruTruncate.  We step
     * back one transaction to avoid passing a cutoff page that hasn't been
     * created yet in the rare case that oldestXact would be the first item on
     * a page and oldestXact == next XID.  In that case, if we didn't subtract
     * one, we'd trigger SimpleLruTruncate's wraparound detection.
     */
    TransactionIdRetreat(oldestXact);
    cutoffPage = TransactionIdToPage(oldestXact);
 
    SimpleLruTruncate(SubTransCtl, cutoffPage);
}

References fb(), SimpleLruTruncate(), SubTransCtl, TransactionIdRetreat, and TransactionIdToPage().

Referenced by CreateCheckPoint(), and CreateRestartPoint().