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Repair two problems with WAL logging of sequence nextvalI() ops, as

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per recent pghackers discussion: force a new WAL record at first nextval
after a checkpoint, and ensure that xlog is flushed to disk if a nextval
record is the only thing emitted by a transaction.
This commit is contained in:
Tom Lane
2002-03-15 19:20:36 +00:00
parent 0b73fe14f1
commit 01747692fe
6 changed files with 147 additions and 68 deletions
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86
src/backend/access/transam/xlog.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.89 2002/03/06 06:09:22 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.90 2002/03/15 19:20:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -131,27 +131,36 @@ bool InRecovery = false;
/*
* MyLastRecPtr points to the start of the last XLOG record inserted by the
* current transaction. If MyLastRecPtr.xrecoff == 0, then we are not in
* a transaction or the transaction has not yet made any loggable changes.
* current transaction. If MyLastRecPtr.xrecoff == 0, then the current
* xact hasn't yet inserted any transaction-controlled XLOG records.
*
* Note that XLOG records inserted outside transaction control are not
* reflected into MyLastRecPtr.
* reflected into MyLastRecPtr. They do, however, cause MyXactMadeXLogEntry
* to be set true. The latter can be used to test whether the current xact
* made any loggable changes (including out-of-xact changes, such as
* sequence updates).
*/
XLogRecPtr MyLastRecPtr = {0, 0};
bool MyXactMadeXLogEntry = false;
/*
* ProcLastRecPtr points to the start of the last XLOG record inserted by the
* current backend. It is updated for all inserts, transaction-controlled
* or not.
* or not. ProcLastRecEnd is similar but points to end+1 of last record.
*/
static XLogRecPtr ProcLastRecPtr = {0, 0};
XLogRecPtr ProcLastRecEnd = {0, 0};
/*
* RedoRecPtr is this backend's local copy of the REDO record pointer
* (which is almost but not quite the same as a pointer to the most recent
* CHECKPOINT record). We update this from the shared-memory copy,
* XLogCtl->Insert.RedoRecPtr, whenever we can safely do so (ie, when we
* hold the Insert lock). See XLogInsert for details.
* hold the Insert lock). See XLogInsert for details. We are also allowed
* to update from XLogCtl->Insert.RedoRecPtr if we hold the info_lck;
* see GetRedoRecPtr.
*/
static XLogRecPtr RedoRecPtr;
@ -272,7 +281,8 @@ typedef struct XLogCtlData
StartUpID ThisStartUpID;
/* This value is not protected by *any* lock... */
XLogRecPtr RedoRecPtr; /* see SetRedoRecPtr/GetRedoRecPtr */
/* see SetSavedRedoRecPtr/GetSavedRedoRecPtr */
XLogRecPtr SavedRedoRecPtr;
slock_t info_lck; /* locks shared LogwrtRqst/LogwrtResult */
} XLogCtlData;
@ -777,6 +787,7 @@ begin:;
MyLastRecPtr = RecPtr;
ProcLastRecPtr = RecPtr;
Insert->PrevRecord = RecPtr;
MyXactMadeXLogEntry = true;
Insert->currpos += SizeOfXLogRecord;
freespace -= SizeOfXLogRecord;
@ -855,6 +866,8 @@ begin:;
SpinLockRelease_NoHoldoff(&xlogctl->info_lck);
}
ProcLastRecEnd = RecPtr;
END_CRIT_SECTION();
return (RecPtr);
@ -2538,7 +2551,7 @@ StartupXLOG(void)
ThisStartUpID = checkPoint.ThisStartUpID;
RedoRecPtr = XLogCtl->Insert.RedoRecPtr =
XLogCtl->RedoRecPtr = checkPoint.redo;
XLogCtl->SavedRedoRecPtr = checkPoint.redo;
if (XLByteLT(RecPtr, checkPoint.redo))
elog(PANIC, "invalid redo in checkpoint record");
@ -2824,32 +2837,47 @@ void
SetThisStartUpID(void)
{
ThisStartUpID = XLogCtl->ThisStartUpID;
RedoRecPtr = XLogCtl->RedoRecPtr;
RedoRecPtr = XLogCtl->SavedRedoRecPtr;
}
/*
* CheckPoint process called by postmaster saves copy of new RedoRecPtr
* in shmem (using SetRedoRecPtr). When checkpointer completes, postmaster
* calls GetRedoRecPtr to update its own copy of RedoRecPtr, so that
* subsequently-spawned backends will start out with a reasonably up-to-date
* local RedoRecPtr. Since these operations are not protected by any lock
* and copying an XLogRecPtr isn't atomic, it's unsafe to use either of these
* routines at other times!
*
* Note: once spawned, a backend must update its local RedoRecPtr from
* XLogCtl->Insert.RedoRecPtr while holding the insert lock. This is
* done in XLogInsert().
* in shmem (using SetSavedRedoRecPtr). When checkpointer completes,
* postmaster calls GetSavedRedoRecPtr to update its own copy of RedoRecPtr,
* so that subsequently-spawned backends will start out with a reasonably
* up-to-date local RedoRecPtr. Since these operations are not protected by
* any lock and copying an XLogRecPtr isn't atomic, it's unsafe to use either
* of these routines at other times!
*/
void
SetRedoRecPtr(void)
SetSavedRedoRecPtr(void)
{
XLogCtl->RedoRecPtr = RedoRecPtr;
XLogCtl->SavedRedoRecPtr = RedoRecPtr;
}
void
GetSavedRedoRecPtr(void)
{
RedoRecPtr = XLogCtl->SavedRedoRecPtr;
}
/*
* Once spawned, a backend may update its local RedoRecPtr from
* XLogCtl->Insert.RedoRecPtr; it must hold the insert lock or info_lck
* to do so. This is done in XLogInsert() or GetRedoRecPtr().
*/
XLogRecPtr
GetRedoRecPtr(void)
{
RedoRecPtr = XLogCtl->RedoRecPtr;
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
SpinLockAcquire_NoHoldoff(&xlogctl->info_lck);
Assert(XLByteLE(RedoRecPtr, xlogctl->Insert.RedoRecPtr));
RedoRecPtr = xlogctl->Insert.RedoRecPtr;
SpinLockRelease_NoHoldoff(&xlogctl->info_lck);
return RedoRecPtr;
}
/*
@ -2862,6 +2890,7 @@ ShutdownXLOG(void)
/* suppress in-transaction check in CreateCheckPoint */
MyLastRecPtr.xrecoff = 0;
MyXactMadeXLogEntry = false;
CritSectionCount++;
CreateDummyCaches();
@ -2886,7 +2915,7 @@ CreateCheckPoint(bool shutdown)
uint32 _logId;
uint32 _logSeg;
if (MyLastRecPtr.xrecoff != 0)
if (MyXactMadeXLogEntry)
elog(ERROR, "CreateCheckPoint: cannot be called inside transaction block");
/*
@ -2972,9 +3001,16 @@ CreateCheckPoint(bool shutdown)
/*
* Here we update the shared RedoRecPtr for future XLogInsert calls;
* this must be done while holding the insert lock.
* this must be done while holding the insert lock AND the info_lck.
*/
RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo;
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
SpinLockAcquire_NoHoldoff(&xlogctl->info_lck);
RedoRecPtr = xlogctl->Insert.RedoRecPtr = checkPoint.redo;
SpinLockRelease_NoHoldoff(&xlogctl->info_lck);
}
/*
* Get UNDO record ptr - this is oldest of PROC->logRec values. We do