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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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43
src/backend/access/transam/twophase.c
View File

@@ -132,7 +132,7 @@ int max_prepared_xacts = 0;
*
* 3. To begin COMMIT PREPARED or ROLLBACK PREPARED, check that the entry is
* valid and not locked, then mark the entry as locked by storing my current
* backend ID into locking_backend. This prevents concurrent attempts to
* proc number into locking_backend. This prevents concurrent attempts to
* commit or rollback the same prepared xact.
*
* 4. On completion of COMMIT PREPARED or ROLLBACK PREPARED, remove the entry
@@ -165,7 +165,7 @@ typedef struct GlobalTransactionData
TransactionId xid; /* The GXACT id */
Oid owner; /* ID of user that executed the xact */
BackendId locking_backend; /* backend currently working on the xact */
ProcNumber locking_backend; /* backend currently working on the xact */
bool valid; /* true if PGPROC entry is in proc array */
bool ondisk; /* true if prepare state file is on disk */
bool inredo; /* true if entry was added via xlog_redo */
@@ -333,7 +333,7 @@ AtAbort_Twophase(void)
if (!MyLockedGxact->valid)
RemoveGXact(MyLockedGxact);
else
MyLockedGxact->locking_backend = InvalidBackendId;
MyLockedGxact->locking_backend = INVALID_PROC_NUMBER;
LWLockRelease(TwoPhaseStateLock);
MyLockedGxact = NULL;
@@ -347,7 +347,7 @@ void
PostPrepare_Twophase(void)
{
LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
MyLockedGxact->locking_backend = InvalidBackendId;
MyLockedGxact->locking_backend = INVALID_PROC_NUMBER;
LWLockRelease(TwoPhaseStateLock);
MyLockedGxact = NULL;
@@ -452,14 +452,14 @@ MarkAsPreparingGuts(GlobalTransaction gxact, TransactionId xid, const char *gid,
{
/* clone VXID, for TwoPhaseGetXidByVirtualXID() to find */
proc->vxid.lxid = MyProc->vxid.lxid;
proc->vxid.backendId = MyBackendId;
proc->vxid.procNumber = MyProcNumber;
}
else
{
Assert(AmStartupProcess() || !IsPostmasterEnvironment);
/* GetLockConflicts() uses this to specify a wait on the XID */
proc->vxid.lxid = xid;
proc->vxid.backendId = InvalidBackendId;
proc->vxid.procNumber = INVALID_PROC_NUMBER;
}
proc->xid = xid;
Assert(proc->xmin == InvalidTransactionId);
@@ -484,7 +484,7 @@ MarkAsPreparingGuts(GlobalTransaction gxact, TransactionId xid, const char *gid,
gxact->prepared_at = prepared_at;
gxact->xid = xid;
gxact->owner = owner;
gxact->locking_backend = MyBackendId;
gxact->locking_backend = MyProcNumber;
gxact->valid = false;
gxact->inredo = false;
strcpy(gxact->gid, gid);
@@ -577,7 +577,7 @@ LockGXact(const char *gid, Oid user)
continue;
/* Found it, but has someone else got it locked? */
if (gxact->locking_backend != InvalidBackendId)
if (gxact->locking_backend != INVALID_PROC_NUMBER)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("prepared transaction with identifier \"%s\" is busy",
@@ -602,7 +602,7 @@ LockGXact(const char *gid, Oid user)
errhint("Connect to the database where the transaction was prepared to finish it.")));
/* OK for me to lock it */
gxact->locking_backend = MyBackendId;
gxact->locking_backend = MyProcNumber;
MyLockedGxact = gxact;
LWLockRelease(TwoPhaseStateLock);
@@ -849,7 +849,7 @@ TwoPhaseGetGXact(TransactionId xid, bool lock_held)
*
* (This won't find recovered xacts.) If more than one matches, return any
* and set "have_more" to true. To witness multiple matches, a single
* BackendId must consume 2^32 LXIDs, with no intervening database restart.
* proc number must consume 2^32 LXIDs, with no intervening database restart.
*/
TransactionId
TwoPhaseGetXidByVirtualXID(VirtualTransactionId vxid,
@@ -873,7 +873,10 @@ TwoPhaseGetXidByVirtualXID(VirtualTransactionId vxid,
GET_VXID_FROM_PGPROC(proc_vxid, *proc);
if (VirtualTransactionIdEquals(vxid, proc_vxid))
{
/* Startup process sets proc->backendId to InvalidBackendId. */
/*
* Startup process sets proc->vxid.procNumber to
* INVALID_PROC_NUMBER.
*/
Assert(!gxact->inredo);
if (result != InvalidTransactionId)
@@ -891,20 +894,20 @@ TwoPhaseGetXidByVirtualXID(VirtualTransactionId vxid,
}
/*
* TwoPhaseGetDummyBackendId
* Get the dummy backend ID for prepared transaction specified by XID
* TwoPhaseGetDummyProcNumber
* Get the dummy proc number for prepared transaction specified by XID
*
* Dummy backend IDs are similar to real backend IDs of real backends.
* They start at MaxBackends + 1, and are unique across all currently active
* real backends and prepared transactions. If lock_held is set to true,
* Dummy proc numbers are similar to proc numbers of real backends. They
* start at MaxBackends, and are unique across all currently active real
* backends and prepared transactions. If lock_held is set to true,
* TwoPhaseStateLock will not be taken, so the caller had better hold it.
*/
BackendId
TwoPhaseGetDummyBackendId(TransactionId xid, bool lock_held)
ProcNumber
TwoPhaseGetDummyProcNumber(TransactionId xid, bool lock_held)
{
GlobalTransaction gxact = TwoPhaseGetGXact(xid, lock_held);
return gxact->pgprocno + 1;
return gxact->pgprocno;
}
/*
@@ -2549,7 +2552,7 @@ PrepareRedoAdd(char *buf, XLogRecPtr start_lsn,
gxact->prepare_end_lsn = end_lsn;
gxact->xid = hdr->xid;
gxact->owner = hdr->owner;
gxact->locking_backend = InvalidBackendId;
gxact->locking_backend = INVALID_PROC_NUMBER;
gxact->valid = false;
gxact->ondisk = XLogRecPtrIsInvalid(start_lsn);
gxact->inredo = true; /* yes, added in redo */