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Transaction IDs wrap around, per my proposal of 13-Aug-01. More

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documentation to come, but the code is all here.  initdb forced.
This commit is contained in:
Tom Lane
2001-08-26 16:56:03 +00:00
parent d1ee78f296
commit bc7d37a525
29 changed files with 617 additions and 171 deletions
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42
src/backend/storage/ipc/sinval.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.39 2001/08/25 18:52:42 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.40 2001/08/26 16:56:00 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -20,6 +20,8 @@
#include "storage/sinval.h"
#include "storage/sinvaladt.h"
#include "utils/tqual.h"
#include "miscadmin.h"
SPINLOCK SInvalLock = (SPINLOCK) NULL;
@@ -210,17 +212,23 @@ TransactionIdIsInProgress(TransactionId xid)
}
/*
* GetXmaxRecent -- returns oldest transaction that was running
* when all current transaction were started.
* It's used by vacuum to decide what deleted
* tuples must be preserved in a table.
* GetOldestXmin -- returns oldest transaction that was running
* when any current transaction was started.
*
* Note: we include all currently running xids in the set of considered xids.
* If allDbs is TRUE then all backends are considered; if allDbs is FALSE
* then only backends running in my own database are considered.
*
* This is used by VACUUM to decide which deleted tuples must be preserved
* in a table. allDbs = TRUE is needed for shared relations, but allDbs =
* FALSE is sufficient for non-shared relations, since only backends in my
* own database could ever see the tuples in them.
*
* Note: we include the currently running xids in the set of considered xids.
* This ensures that if a just-started xact has not yet set its snapshot,
* when it does set the snapshot it cannot set xmin less than what we compute.
*/
void
GetXmaxRecent(TransactionId *XmaxRecent)
TransactionId
GetOldestXmin(bool allDbs)
{
SISeg *segP = shmInvalBuffer;
ProcState *stateP = segP->procState;
@@ -238,24 +246,28 @@ GetXmaxRecent(TransactionId *XmaxRecent)
if (pOffset != INVALID_OFFSET)
{
PROC *proc = (PROC *) MAKE_PTR(pOffset);
/* Fetch xid just once - see GetNewTransactionId */
TransactionId xid = proc->xid;
if (TransactionIdIsNormal(xid))
if (allDbs || proc->databaseId == MyDatabaseId)
{
if (TransactionIdPrecedes(xid, result))
result = xid;
xid = proc->xmin;
/* Fetch xid just once - see GetNewTransactionId */
TransactionId xid = proc->xid;
if (TransactionIdIsNormal(xid))
{
if (TransactionIdPrecedes(xid, result))
result = xid;
xid = proc->xmin;
if (TransactionIdIsNormal(xid))
if (TransactionIdPrecedes(xid, result))
result = xid;
}
}
}
}
SpinRelease(SInvalLock);
*XmaxRecent = result;
return result;
}
/*----------