Add a comment to distinguish backend types

The data checksums entries were seemingly auxiliary processes from
reading the code, but they are in fact background workers.  Add a
comment to clarify.  Backpatch down to v19 where online checksums
were introduced.

Author: Daniel Gustafsson <daniel@yesql.se>
Reported-by: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwFsBjQs2fv7b72hxzGV_fJMh6LAg4E83pNfDOu1jVgWCA@mail.gmail.com
Backpatch-through: 19

diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 7170a4bff9896b3bfc0a68d9d17b4e22de85acfa..0fc59af02b9fcbb501c7c1a3a0645391970585f6 100644 (file)
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -370,6 +370,10 @@ typedef enum BackendType
        B_WAL_SUMMARIZER,
        B_WAL_WRITER,
 
        B_WAL_SUMMARIZER,
        B_WAL_WRITER,
 

+       /*
+        * Data checksums processes are dynamic background workers, but they use
+        * dedicated backend types for pgstat I/O accounting.
+        */

        B_DATACHECKSUMSWORKER_LAUNCHER,
        B_DATACHECKSUMSWORKER_WORKER,
 
        B_DATACHECKSUMSWORKER_LAUNCHER,
        B_DATACHECKSUMSWORKER_WORKER,