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Replace BackendIds with 0-based ProcNumbers

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Now that BackendId was just another index into the proc array, it was
redundant with the 0-based proc numbers used in other places. Replace
all usage of backend IDs with proc numbers.

The only place where the term "backend id" remains is in a few pgstat
functions that expose backend IDs at the SQL level. Those IDs are now
in fact 0-based ProcNumbers too, but the documentation still calls
them "backend ids". That term still seems appropriate to describe what
the numbers are, so I let it be.

One user-visible effect is that pg_temp_0 is now a valid temp schema
name, for backend with ProcNumber 0.

Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
This commit is contained in:
Heikki Linnakangas
2024-03-03 19:38:22 +02:00
parent ab355e3a88
commit 024c521117
71 changed files with 571 additions and 579 deletions
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44
src/backend/storage/ipc/procarray.c
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@@ -818,9 +818,9 @@ ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
* If the list was not empty, the leader will clear our XID. It is
* impossible to have followers without a leader because the first process
* that has added itself to the list will always have nextidx as
* INVALID_PGPROCNO.
* INVALID_PROC_NUMBER.
*/
if (nextidx != INVALID_PGPROCNO)
if (nextidx != INVALID_PROC_NUMBER)
{
int extraWaits = 0;
@@ -836,7 +836,7 @@ ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
}
pgstat_report_wait_end();
Assert(pg_atomic_read_u32(&proc->procArrayGroupNext) == INVALID_PGPROCNO);
Assert(pg_atomic_read_u32(&proc->procArrayGroupNext) == INVALID_PROC_NUMBER);
/* Fix semaphore count for any absorbed wakeups */
while (extraWaits-- > 0)
@@ -853,13 +853,13 @@ ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
* to pop elements one at a time could lead to an ABA problem.
*/
nextidx = pg_atomic_exchange_u32(&procglobal->procArrayGroupFirst,
INVALID_PGPROCNO);
INVALID_PROC_NUMBER);
/* Remember head of list so we can perform wakeups after dropping lock. */
wakeidx = nextidx;
/* Walk the list and clear all XIDs. */
while (nextidx != INVALID_PGPROCNO)
while (nextidx != INVALID_PROC_NUMBER)
{
PGPROC *nextproc = &allProcs[nextidx];
@@ -879,12 +879,12 @@ ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
* up are probably much slower than the simple memory writes we did while
* holding the lock.
*/
while (wakeidx != INVALID_PGPROCNO)
while (wakeidx != INVALID_PROC_NUMBER)
{
PGPROC *nextproc = &allProcs[wakeidx];
wakeidx = pg_atomic_read_u32(&nextproc->procArrayGroupNext);
pg_atomic_write_u32(&nextproc->procArrayGroupNext, INVALID_PGPROCNO);
pg_atomic_write_u32(&nextproc->procArrayGroupNext, INVALID_PROC_NUMBER);
/* ensure all previous writes are visible before follower continues. */
pg_write_barrier();
@@ -2538,7 +2538,7 @@ ProcArrayInstallImportedXmin(TransactionId xmin,
/*
* Find the PGPROC entry of the source transaction. (This could use
* GetPGProcByBackendId(), unless it's a prepared xact. But this isn't
* GetPGProcByNumber(), unless it's a prepared xact. But this isn't
* performance critical.)
*/
for (index = 0; index < arrayP->numProcs; index++)
@@ -2553,7 +2553,7 @@ ProcArrayInstallImportedXmin(TransactionId xmin,
continue;
/* We are only interested in the specific virtual transaction. */
if (proc->vxid.backendId != sourcevxid->backendId)
if (proc->vxid.procNumber != sourcevxid->procNumber)
continue;
if (proc->vxid.lxid != sourcevxid->localTransactionId)
continue;
@@ -3105,20 +3105,20 @@ HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids, int type)
}
/*
* BackendIdGetProc -- get a backend's PGPROC given its backend ID
* ProcNumberGetProc -- get a backend's PGPROC given its proc number
*
* The result may be out of date arbitrarily quickly, so the caller
* must be careful about how this information is used. NULL is
* returned if the backend is not active.
*/
PGPROC *
BackendIdGetProc(int backendID)
ProcNumberGetProc(ProcNumber procNumber)
{
PGPROC *result;
if (backendID < 1 || backendID > ProcGlobal->allProcCount)
if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
return NULL;
result = GetPGProcByBackendId(backendID);
result = GetPGProcByNumber(procNumber);
if (result->pid == 0)
return NULL;
@@ -3127,15 +3127,15 @@ BackendIdGetProc(int backendID)
}
/*
* BackendIdGetTransactionIds -- get a backend's transaction status
* ProcNumberGetTransactionIds -- get a backend's transaction status
*
* Get the xid, xmin, nsubxid and overflow status of the backend. The
* result may be out of date arbitrarily quickly, so the caller must be
* careful about how this information is used.
*/
void
BackendIdGetTransactionIds(int backendID, TransactionId *xid,
TransactionId *xmin, int *nsubxid, bool *overflowed)
ProcNumberGetTransactionIds(ProcNumber procNumber, TransactionId *xid,
TransactionId *xmin, int *nsubxid, bool *overflowed)
{
PGPROC *proc;
@@ -3144,9 +3144,9 @@ BackendIdGetTransactionIds(int backendID, TransactionId *xid,
*nsubxid = 0;
*overflowed = false;
if (backendID < 1 || backendID > ProcGlobal->allProcCount)
if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
return;
proc = GetPGProcByBackendId(backendID);
proc = GetPGProcByNumber(procNumber);
/* Need to lock out additions/removals of backends */
LWLockAcquire(ProcArrayLock, LW_SHARED);
@@ -3453,7 +3453,7 @@ GetConflictingVirtualXIDs(TransactionId limitXmin, Oid dbOid)
LWLockRelease(ProcArrayLock);
/* add the terminator */
vxids[count].backendId = InvalidBackendId;
vxids[count].procNumber = INVALID_PROC_NUMBER;
vxids[count].localTransactionId = InvalidLocalTransactionId;
return vxids;
@@ -3488,7 +3488,7 @@ SignalVirtualTransaction(VirtualTransactionId vxid, ProcSignalReason sigmode,
GET_VXID_FROM_PGPROC(procvxid, *proc);
if (procvxid.backendId == vxid.backendId &&
if (procvxid.procNumber == vxid.procNumber &&
procvxid.localTransactionId == vxid.localTransactionId)
{
proc->recoveryConflictPending = conflictPending;
@@ -3499,7 +3499,7 @@ SignalVirtualTransaction(VirtualTransactionId vxid, ProcSignalReason sigmode,
* Kill the pid if it's still here. If not, that's what we
* wanted so ignore any errors.
*/
(void) SendProcSignal(pid, sigmode, vxid.backendId);
(void) SendProcSignal(pid, sigmode, vxid.procNumber);
}
break;
}
@@ -3662,7 +3662,7 @@ CancelDBBackends(Oid databaseid, ProcSignalReason sigmode, bool conflictPending)
* Kill the pid if it's still here. If not, that's what we
* wanted so ignore any errors.
*/
(void) SendProcSignal(pid, sigmode, procvxid.backendId);
(void) SendProcSignal(pid, sigmode, procvxid.procNumber);
}
}
}