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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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50
src/backend/utils/activity/backend_status.c
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@@ -238,7 +238,7 @@ CreateSharedBackendStatus(void)
/*
* Initialize pgstats backend activity state, and set up our on-proc-exit
* hook. Called from InitPostgres and AuxiliaryProcessMain. MyBackendId must
* hook. Called from InitPostgres and AuxiliaryProcessMain. MyProcNumber must
* be set, but we must not have started any transaction yet (since the exit
* hook must run after the last transaction exit).
*
@@ -248,9 +248,9 @@ void
pgstat_beinit(void)
{
/* Initialize MyBEEntry */
Assert(MyBackendId != InvalidBackendId);
Assert(MyBackendId >= 1 && MyBackendId <= NumBackendStatSlots);
MyBEEntry = &BackendStatusArray[MyBackendId - 1];
Assert(MyProcNumber != INVALID_PROC_NUMBER);
Assert(MyProcNumber >= 0 && MyProcNumber < NumBackendStatSlots);
MyBEEntry = &BackendStatusArray[MyProcNumber];
/* Set up a process-exit hook to clean up */
on_shmem_exit(pgstat_beshutdown_hook, 0);
@@ -721,7 +721,7 @@ pgstat_read_current_status(void)
#ifdef ENABLE_GSS
PgBackendGSSStatus *localgssstatus;
#endif
int i;
ProcNumber procNumber;
if (localBackendStatusTable)
return; /* already done */
@@ -764,7 +764,7 @@ pgstat_read_current_status(void)
beentry = BackendStatusArray;
localentry = localtable;
for (i = 1; i <= NumBackendStatSlots; i++)
for (procNumber = 0; procNumber < NumBackendStatSlots; procNumber++)
{
/*
* Follow the protocol of retrying if st_changecount changes while we
@@ -830,17 +830,17 @@ pgstat_read_current_status(void)
if (localentry->backendStatus.st_procpid > 0)
{
/*
* The BackendStatusArray index is exactly the BackendId of the
* The BackendStatusArray index is exactly the ProcNumber of the
* source backend. Note that this means localBackendStatusTable
* is in order by backend_id. pgstat_get_beentry_by_backend_id()
* is in order by proc_number. pgstat_get_beentry_by_backend_id()
* depends on that.
*/
localentry->backend_id = i;
BackendIdGetTransactionIds(i,
&localentry->backend_xid,
&localentry->backend_xmin,
&localentry->backend_subxact_count,
&localentry->backend_subxact_overflowed);
localentry->proc_number = procNumber;
ProcNumberGetTransactionIds(procNumber,
&localentry->backend_xid,
&localentry->backend_xmin,
&localentry->backend_subxact_count,
&localentry->backend_subxact_overflowed);
localentry++;
localappname += NAMEDATALEN;
@@ -1043,7 +1043,7 @@ pgstat_get_my_query_id(void)
* cmp_lbestatus
*
* Comparison function for bsearch() on an array of LocalPgBackendStatus.
* The backend_id field is used to compare the arguments.
* The proc_number field is used to compare the arguments.
* ----------
*/
static int
@@ -1052,17 +1052,17 @@ cmp_lbestatus(const void *a, const void *b)
const LocalPgBackendStatus *lbestatus1 = (const LocalPgBackendStatus *) a;
const LocalPgBackendStatus *lbestatus2 = (const LocalPgBackendStatus *) b;
return lbestatus1->backend_id - lbestatus2->backend_id;
return lbestatus1->proc_number - lbestatus2->proc_number;
}
/* ----------
* pgstat_get_beentry_by_backend_id() -
* pgstat_get_beentry_by_proc_number() -
*
* Support function for the SQL-callable pgstat* functions. Returns
* our local copy of the current-activity entry for one backend,
* or NULL if the given beid doesn't identify any known session.
*
* The beid argument is the BackendId of the desired session
* The argument is the ProcNumber of the desired session
* (note that this is unlike pgstat_get_local_beentry_by_index()).
*
* NB: caller is responsible for a check if the user is permitted to see
@@ -1070,9 +1070,9 @@ cmp_lbestatus(const void *a, const void *b)
* ----------
*/
PgBackendStatus *
pgstat_get_beentry_by_backend_id(BackendId beid)
pgstat_get_beentry_by_proc_number(ProcNumber procNumber)
{
LocalPgBackendStatus *ret = pgstat_get_local_beentry_by_backend_id(beid);
LocalPgBackendStatus *ret = pgstat_get_local_beentry_by_proc_number(procNumber);
if (ret)
return &ret->backendStatus;
@@ -1082,12 +1082,12 @@ pgstat_get_beentry_by_backend_id(BackendId beid)
/* ----------
* pgstat_get_local_beentry_by_backend_id() -
* pgstat_get_local_beentry_by_proc_number() -
*
* Like pgstat_get_beentry_by_backend_id() but with locally computed additions
* Like pgstat_get_beentry_by_proc_number() but with locally computed additions
* (like xid and xmin values of the backend)
*
* The beid argument is the BackendId of the desired session
* The argument is the ProcNumber of the desired session
* (note that this is unlike pgstat_get_local_beentry_by_index()).
*
* NB: caller is responsible for checking if the user is permitted to see this
@@ -1095,7 +1095,7 @@ pgstat_get_beentry_by_backend_id(BackendId beid)
* ----------
*/
LocalPgBackendStatus *
pgstat_get_local_beentry_by_backend_id(BackendId beid)
pgstat_get_local_beentry_by_proc_number(ProcNumber procNumber)
{
LocalPgBackendStatus key;
@@ -1105,7 +1105,7 @@ pgstat_get_local_beentry_by_backend_id(BackendId beid)
* Since the localBackendStatusTable is in order by backend_id, we can use
* bsearch() to search it efficiently.
*/
key.backend_id = beid;
key.proc_number = procNumber;
return bsearch(&key, localBackendStatusTable, localNumBackends,
sizeof(LocalPgBackendStatus), cmp_lbestatus);
}