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, 1 insertions, 1 deletions

diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index 03f78b5b25f..46f95f7c8a6 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -72,7 +72,7 @@ extern void ShmemBackendArrayAllocation(void);
  * by using a 64bit state; but it's unlikely to be worthwhile as 2^18-1
  * backends exceed currently realistic configurations. Even if that limitation
  * were removed, we still could not a) exceed 2^23-1 because inval.c stores
- * the backend ID as a 3-byte signed integer, b) INT_MAX/4 because some places
+ * the ProcNumber as a 3-byte signed integer, b) INT_MAX/4 because some places
  * compute 4*MaxBackends without any overflow check.  This is rechecked in the
  * relevant GUC check hooks and in RegisterBackgroundWorker().
  */