Replace BackendIds with 0-based ProcNumbers

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

1 files changed, 25 insertions, 25 deletions

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 30a20635057..d1e9aa8290f 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -213,7 +213,7 @@ pg_stat_get_backend_idset(PG_FUNCTION_ARGS)
 		/* do when there is more left to send */
 		LocalPgBackendStatus *local_beentry = pgstat_get_local_beentry_by_index(fctx[0]);
 
-		SRF_RETURN_NEXT(funcctx, Int32GetDatum(local_beentry->backend_id));
+		SRF_RETURN_NEXT(funcctx, Int32GetDatum(local_beentry->proc_number));
 	}
 	else
 	{
@@ -669,10 +669,10 @@ pg_backend_pid(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_pid(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	PG_RETURN_INT32(beentry->st_procpid);
@@ -682,10 +682,10 @@ pg_stat_get_backend_pid(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_dbid(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	PG_RETURN_OID(beentry->st_databaseid);
@@ -695,10 +695,10 @@ pg_stat_get_backend_dbid(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_userid(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	PG_RETURN_OID(beentry->st_userid);
@@ -711,7 +711,7 @@ pg_stat_get_backend_subxact(PG_FUNCTION_ARGS)
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_SUBXACT_COLS] = {0};
 	bool		nulls[PG_STAT_GET_SUBXACT_COLS] = {0};
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	LocalPgBackendStatus *local_beentry;
 
 	/* Initialise attributes information in the tuple descriptor */
@@ -723,7 +723,7 @@ pg_stat_get_backend_subxact(PG_FUNCTION_ARGS)
 
 	BlessTupleDesc(tupdesc);
 
-	if ((local_beentry = pgstat_get_local_beentry_by_backend_id(beid)) != NULL)
+	if ((local_beentry = pgstat_get_local_beentry_by_proc_number(procNumber)) != NULL)
 	{
 		/* Fill values and NULLs */
 		values[0] = Int32GetDatum(local_beentry->backend_subxact_count);
@@ -742,13 +742,13 @@ pg_stat_get_backend_subxact(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_activity(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 	const char *activity;
 	char	   *clipped_activity;
 	text	   *ret;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		activity = "<backend information not available>";
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
 		activity = "<insufficient privilege>";
@@ -767,12 +767,12 @@ pg_stat_get_backend_activity(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_wait_event_type(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 	PGPROC	   *proc;
 	const char *wait_event_type = NULL;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		wait_event_type = "<backend information not available>";
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
 		wait_event_type = "<insufficient privilege>";
@@ -788,12 +788,12 @@ pg_stat_get_backend_wait_event_type(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_wait_event(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 	PGPROC	   *proc;
 	const char *wait_event = NULL;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		wait_event = "<backend information not available>";
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
 		wait_event = "<insufficient privilege>";
@@ -810,11 +810,11 @@ pg_stat_get_backend_wait_event(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_activity_start(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	TimestampTz result;
 	PgBackendStatus *beentry;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
@@ -836,11 +836,11 @@ pg_stat_get_backend_activity_start(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_xact_start(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	TimestampTz result;
 	PgBackendStatus *beentry;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
@@ -858,11 +858,11 @@ pg_stat_get_backend_xact_start(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_start(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	TimestampTz result;
 	PgBackendStatus *beentry;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
@@ -880,13 +880,13 @@ pg_stat_get_backend_start(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 	SockAddr	zero_clientaddr;
 	char		remote_host[NI_MAXHOST];
 	int			ret;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
@@ -925,13 +925,13 @@ pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_client_port(PG_FUNCTION_ARGS)
 {
-	int32		beid = PG_GETARG_INT32(0);
+	int32		procNumber = PG_GETARG_INT32(0);
 	PgBackendStatus *beentry;
 	SockAddr	zero_clientaddr;
 	char		remote_port[NI_MAXSERV];
 	int			ret;
 
-	if ((beentry = pgstat_get_beentry_by_backend_id(beid)) == NULL)
+	if ((beentry = pgstat_get_beentry_by_proc_number(procNumber)) == NULL)
 		PG_RETURN_NULL();
 
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))