Fix incorrect comment on how BackendStatusArray is indexed

The comment was copy-pasted from the call to ProcSignalInit() in
AuxiliaryProcessMain(), which uses a similar scheme of having reserved
slots for aux processes after MaxBackends slots for backends. However,
ProcSignalInit() indexing starts from 1, whereas BackendStatusArray
starts from 0. The code is correct, but the comment was wrong.

Discussion: https://www.postgresql.org/message-id/f3ecd4cb-85ee-4e54-8278-5fabfb3a4ed0@iki.fi
Backpatch-through: v14

diff --git a/src/backend/utils/activity/backend_status.c b/src/backend/utils/activity/backend_status.c
index 6917ef4c4ba355e607b17d012924f59fd8dd7824..76b6584d6947df715497a0cdd62e8846efd14d8c 100644 (file)
--- a/src/backend/utils/activity/backend_status.c
+++ b/src/backend/utils/activity/backend_status.c
@@ -263,9 +263,9 @@ pgstat_beinit(void)
         * Assign the MyBEEntry for an auxiliary process.  Since it doesn't
         * have a BackendId, the slot is statically allocated based on the
         * auxiliary process type (MyAuxProcType).  Backends use slots indexed
-        * in the range from 1 to MaxBackends (inclusive), so we use
-        * MaxBackends + AuxBackendType + 1 as the index of the slot for an
-        * auxiliary process.
+        * in the range from 0 to MaxBackends (exclusive), so we use
+        * MaxBackends + AuxProcType as the index of the slot for an auxiliary
+        * process.
         */
        MyBEEntry = &BackendStatusArray[MaxBackends + MyAuxProcType];
    }