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, 5 insertions, 5 deletions

diff --git a/src/backend/libpq/pqmq.c b/src/backend/libpq/pqmq.c
index 5764f8b2225..00a44ca803f 100644
--- a/src/backend/libpq/pqmq.c
+++ b/src/backend/libpq/pqmq.c
@@ -26,7 +26,7 @@
 static shm_mq_handle *pq_mq_handle;
 static bool pq_mq_busy = false;
 static pid_t pq_mq_parallel_leader_pid = 0;
-static pid_t pq_mq_parallel_leader_backend_id = InvalidBackendId;
+static pid_t pq_mq_parallel_leader_proc_number = INVALID_PROC_NUMBER;
 
 static void pq_cleanup_redirect_to_shm_mq(dsm_segment *seg, Datum arg);
 static void mq_comm_reset(void);
@@ -75,11 +75,11 @@ pq_cleanup_redirect_to_shm_mq(dsm_segment *seg, Datum arg)
  * message data via the shm_mq.
  */
 void
-pq_set_parallel_leader(pid_t pid, BackendId backend_id)
+pq_set_parallel_leader(pid_t pid, ProcNumber procNumber)
 {
 	Assert(PqCommMethods == &PqCommMqMethods);
 	pq_mq_parallel_leader_pid = pid;
-	pq_mq_parallel_leader_backend_id = backend_id;
+	pq_mq_parallel_leader_proc_number = procNumber;
 }
 
 static void
@@ -168,13 +168,13 @@ mq_putmessage(char msgtype, const char *s, size_t len)
 			if (IsLogicalParallelApplyWorker())
 				SendProcSignal(pq_mq_parallel_leader_pid,
 							   PROCSIG_PARALLEL_APPLY_MESSAGE,
-							   pq_mq_parallel_leader_backend_id);
+							   pq_mq_parallel_leader_proc_number);
 			else
 			{
 				Assert(IsParallelWorker());
 				SendProcSignal(pq_mq_parallel_leader_pid,
 							   PROCSIG_PARALLEL_MESSAGE,
-							   pq_mq_parallel_leader_backend_id);
+							   pq_mq_parallel_leader_proc_number);
 			}
 		}