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, 12 insertions, 12 deletions

diff --git a/src/common/relpath.c b/src/common/relpath.c
index d9214f915c9..f54c36ef7ac 100644
--- a/src/common/relpath.c
+++ b/src/common/relpath.c
@@ -20,7 +20,7 @@
 
 #include "catalog/pg_tablespace_d.h"
 #include "common/relpath.h"
-#include "storage/backendid.h"
+#include "storage/procnumber.h"
 
 
 /*
@@ -133,13 +133,13 @@ GetDatabasePath(Oid dbOid, Oid spcOid)
  *
  * Result is a palloc'd string.
  *
- * Note: ideally, backendId would be declared as type BackendId, but relpath.h
- * would have to include a backend-only header to do that; doesn't seem worth
- * the trouble considering BackendId is just int anyway.
+ * Note: ideally, procNumber would be declared as type ProcNumber, but
+ * relpath.h would have to include a backend-only header to do that; doesn't
+ * seem worth the trouble considering ProcNumber is just int anyway.
  */
 char *
 GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
-				int backendId, ForkNumber forkNumber)
+				int procNumber, ForkNumber forkNumber)
 {
 	char	   *path;
 
@@ -147,7 +147,7 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 	{
 		/* Shared system relations live in {datadir}/global */
 		Assert(dbOid == 0);
-		Assert(backendId == InvalidBackendId);
+		Assert(procNumber == INVALID_PROC_NUMBER);
 		if (forkNumber != MAIN_FORKNUM)
 			path = psprintf("global/%u_%s",
 							relNumber, forkNames[forkNumber]);
@@ -157,7 +157,7 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 	else if (spcOid == DEFAULTTABLESPACE_OID)
 	{
 		/* The default tablespace is {datadir}/base */
-		if (backendId == InvalidBackendId)
+		if (procNumber == INVALID_PROC_NUMBER)
 		{
 			if (forkNumber != MAIN_FORKNUM)
 				path = psprintf("base/%u/%u_%s",
@@ -171,17 +171,17 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 		{
 			if (forkNumber != MAIN_FORKNUM)
 				path = psprintf("base/%u/t%d_%u_%s",
-								dbOid, backendId, relNumber,
+								dbOid, procNumber, relNumber,
 								forkNames[forkNumber]);
 			else
 				path = psprintf("base/%u/t%d_%u",
-								dbOid, backendId, relNumber);
+								dbOid, procNumber, relNumber);
 		}
 	}
 	else
 	{
 		/* All other tablespaces are accessed via symlinks */
-		if (backendId == InvalidBackendId)
+		if (procNumber == INVALID_PROC_NUMBER)
 		{
 			if (forkNumber != MAIN_FORKNUM)
 				path = psprintf("pg_tblspc/%u/%s/%u/%u_%s",
@@ -198,12 +198,12 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 			if (forkNumber != MAIN_FORKNUM)
 				path = psprintf("pg_tblspc/%u/%s/%u/t%d_%u_%s",
 								spcOid, TABLESPACE_VERSION_DIRECTORY,
-								dbOid, backendId, relNumber,
+								dbOid, procNumber, relNumber,
 								forkNames[forkNumber]);
 			else
 				path = psprintf("pg_tblspc/%u/%s/%u/t%d_%u",
 								spcOid, TABLESPACE_VERSION_DIRECTORY,
-								dbOid, backendId, relNumber);
+								dbOid, procNumber, relNumber);
 		}
 	}
 	return path;