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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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64
src/backend/access/transam/multixact.c
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@@ -237,11 +237,11 @@ typedef struct MultiXactStateData
/*
* Per-backend data starts here. We have two arrays stored in the area
* immediately following the MultiXactStateData struct. Each is indexed by
* BackendId.
* ProcNumber.
*
* In both arrays, there's a slot for all normal backends (1..MaxBackends)
* followed by a slot for max_prepared_xacts prepared transactions. Valid
* BackendIds start from 1; element zero of each array is never used.
* In both arrays, there's a slot for all normal backends
* (0..MaxBackends-1) followed by a slot for max_prepared_xacts prepared
* transactions.
*
* OldestMemberMXactId[k] is the oldest MultiXactId each backend's current
* transaction(s) could possibly be a member of, or InvalidMultiXactId
@@ -285,8 +285,7 @@ typedef struct MultiXactStateData
} MultiXactStateData;
/*
* Last element of OldestMemberMXactId and OldestVisibleMXactId arrays.
* Valid elements are (1..MaxOldestSlot); element 0 is never used.
* Size of OldestMemberMXactId and OldestVisibleMXactId arrays.
*/
#define MaxOldestSlot (MaxBackends + max_prepared_xacts)
@@ -397,7 +396,7 @@ MultiXactIdCreate(TransactionId xid1, MultiXactStatus status1,
Assert(!TransactionIdEquals(xid1, xid2) || (status1 != status2));
/* MultiXactIdSetOldestMember() must have been called already. */
Assert(MultiXactIdIsValid(OldestMemberMXactId[MyBackendId]));
Assert(MultiXactIdIsValid(OldestMemberMXactId[MyProcNumber]));
/*
* Note: unlike MultiXactIdExpand, we don't bother to check that both XIDs
@@ -451,7 +450,7 @@ MultiXactIdExpand(MultiXactId multi, TransactionId xid, MultiXactStatus status)
Assert(TransactionIdIsValid(xid));
/* MultiXactIdSetOldestMember() must have been called already. */
Assert(MultiXactIdIsValid(OldestMemberMXactId[MyBackendId]));
Assert(MultiXactIdIsValid(OldestMemberMXactId[MyProcNumber]));
debug_elog5(DEBUG2, "Expand: received multi %u, xid %u status %s",
multi, xid, mxstatus_to_string(status));
@@ -626,7 +625,7 @@ MultiXactIdIsRunning(MultiXactId multi, bool isLockOnly)
void
MultiXactIdSetOldestMember(void)
{
if (!MultiXactIdIsValid(OldestMemberMXactId[MyBackendId]))
if (!MultiXactIdIsValid(OldestMemberMXactId[MyProcNumber]))
{
MultiXactId nextMXact;
@@ -655,12 +654,12 @@ MultiXactIdSetOldestMember(void)
if (nextMXact < FirstMultiXactId)
nextMXact = FirstMultiXactId;
OldestMemberMXactId[MyBackendId] = nextMXact;
OldestMemberMXactId[MyProcNumber] = nextMXact;
LWLockRelease(MultiXactGenLock);
debug_elog4(DEBUG2, "MultiXact: setting OldestMember[%d] = %u",
MyBackendId, nextMXact);
MyProcNumber, nextMXact);
}
}
@@ -683,7 +682,7 @@ MultiXactIdSetOldestMember(void)
static void
MultiXactIdSetOldestVisible(void)
{
if (!MultiXactIdIsValid(OldestVisibleMXactId[MyBackendId]))
if (!MultiXactIdIsValid(OldestVisibleMXactId[MyProcNumber]))
{
MultiXactId oldestMXact;
int i;
@@ -699,7 +698,7 @@ MultiXactIdSetOldestVisible(void)
if (oldestMXact < FirstMultiXactId)
oldestMXact = FirstMultiXactId;
for (i = 1; i <= MaxOldestSlot; i++)
for (i = 0; i < MaxOldestSlot; i++)
{
MultiXactId thisoldest = OldestMemberMXactId[i];
@@ -708,12 +707,12 @@ MultiXactIdSetOldestVisible(void)
oldestMXact = thisoldest;
}
OldestVisibleMXactId[MyBackendId] = oldestMXact;
OldestVisibleMXactId[MyProcNumber] = oldestMXact;
LWLockRelease(MultiXactGenLock);
debug_elog4(DEBUG2, "MultiXact: setting OldestVisible[%d] = %u",
MyBackendId, oldestMXact);
MyProcNumber, oldestMXact);
}
}
@@ -1285,7 +1284,7 @@ GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **members,
* multi. It cannot possibly still be running.
*/
if (isLockOnly &&
MultiXactIdPrecedes(multi, OldestVisibleMXactId[MyBackendId]))
MultiXactIdPrecedes(multi, OldestVisibleMXactId[MyProcNumber]))
{
debug_elog2(DEBUG2, "GetMembers: a locker-only multi is too old");
*members = NULL;
@@ -1752,8 +1751,8 @@ AtEOXact_MultiXact(void)
* We assume that storing a MultiXactId is atomic and so we need not take
* MultiXactGenLock to do this.
*/
OldestMemberMXactId[MyBackendId] = InvalidMultiXactId;
OldestVisibleMXactId[MyBackendId] = InvalidMultiXactId;
OldestMemberMXactId[MyProcNumber] = InvalidMultiXactId;
OldestVisibleMXactId[MyProcNumber] = InvalidMultiXactId;
/*
* Discard the local MultiXactId cache. Since MXactContext was created as
@@ -1773,7 +1772,7 @@ AtEOXact_MultiXact(void)
void
AtPrepare_MultiXact(void)
{
MultiXactId myOldestMember = OldestMemberMXactId[MyBackendId];
MultiXactId myOldestMember = OldestMemberMXactId[MyProcNumber];
if (MultiXactIdIsValid(myOldestMember))
RegisterTwoPhaseRecord(TWOPHASE_RM_MULTIXACT_ID, 0,
@@ -1793,10 +1792,10 @@ PostPrepare_MultiXact(TransactionId xid)
* Transfer our OldestMemberMXactId value to the slot reserved for the
* prepared transaction.
*/
myOldestMember = OldestMemberMXactId[MyBackendId];
myOldestMember = OldestMemberMXactId[MyProcNumber];
if (MultiXactIdIsValid(myOldestMember))
{
BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid, false);
ProcNumber dummyProcNumber = TwoPhaseGetDummyProcNumber(xid, false);
/*
* Even though storing MultiXactId is atomic, acquire lock to make
@@ -1806,8 +1805,8 @@ PostPrepare_MultiXact(TransactionId xid)
*/
LWLockAcquire(MultiXactGenLock, LW_EXCLUSIVE);
OldestMemberMXactId[dummyBackendId] = myOldestMember;
OldestMemberMXactId[MyBackendId] = InvalidMultiXactId;
OldestMemberMXactId[dummyProcNumber] = myOldestMember;
OldestMemberMXactId[MyProcNumber] = InvalidMultiXactId;
LWLockRelease(MultiXactGenLock);
}
@@ -1820,7 +1819,7 @@ PostPrepare_MultiXact(TransactionId xid)
* We assume that storing a MultiXactId is atomic and so we need not take
* MultiXactGenLock to do this.
*/
OldestVisibleMXactId[MyBackendId] = InvalidMultiXactId;
OldestVisibleMXactId[MyProcNumber] = InvalidMultiXactId;
/*
* Discard the local MultiXactId cache like in AtEOXact_MultiXact.
@@ -1837,7 +1836,7 @@ void
multixact_twophase_recover(TransactionId xid, uint16 info,
void *recdata, uint32 len)
{
BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid, false);
ProcNumber dummyProcNumber = TwoPhaseGetDummyProcNumber(xid, false);
MultiXactId oldestMember;
/*
@@ -1847,7 +1846,7 @@ multixact_twophase_recover(TransactionId xid, uint16 info,
Assert(len == sizeof(MultiXactId));
oldestMember = *((MultiXactId *) recdata);
OldestMemberMXactId[dummyBackendId] = oldestMember;
OldestMemberMXactId[dummyProcNumber] = oldestMember;
}
/*
@@ -1858,11 +1857,11 @@ void
multixact_twophase_postcommit(TransactionId xid, uint16 info,
void *recdata, uint32 len)
{
BackendId dummyBackendId = TwoPhaseGetDummyBackendId(xid, true);
ProcNumber dummyProcNumber = TwoPhaseGetDummyProcNumber(xid, true);
Assert(len == sizeof(MultiXactId));
OldestMemberMXactId[dummyBackendId] = InvalidMultiXactId;
OldestMemberMXactId[dummyProcNumber] = InvalidMultiXactId;
}
/*
@@ -1886,9 +1885,9 @@ MultiXactShmemSize(void)
{
Size size;
/* We need 2*MaxOldestSlot + 1 perBackendXactIds[] entries */
/* We need 2*MaxOldestSlot perBackendXactIds[] entries */
#define SHARED_MULTIXACT_STATE_SIZE \
add_size(offsetof(MultiXactStateData, perBackendXactIds) + sizeof(MultiXactId), \
add_size(offsetof(MultiXactStateData, perBackendXactIds), \
mul_size(sizeof(MultiXactId) * 2, MaxOldestSlot))
size = SHARED_MULTIXACT_STATE_SIZE;
@@ -1938,8 +1937,7 @@ MultiXactShmemInit(void)
Assert(found);
/*
* Set up array pointers. Note that perBackendXactIds[0] is wasted space
* since we only use indexes 1..MaxOldestSlot in each array.
* Set up array pointers.
*/
OldestMemberMXactId = MultiXactState->perBackendXactIds;
OldestVisibleMXactId = OldestMemberMXactId + MaxOldestSlot;
@@ -2617,7 +2615,7 @@ GetOldestMultiXactId(void)
nextMXact = FirstMultiXactId;
oldestMXact = nextMXact;
for (i = 1; i <= MaxOldestSlot; i++)
for (i = 0; i < MaxOldestSlot; i++)
{
MultiXactId thisoldest;