Doc: improve explanation of when custom GUCs appear in pg_settings.

Be more clear about when and how an extension-defined GUC comes to be
visible in pg_settings.  (Move the para to the bottom of the page, too;
whoever thought this point was more important than the para about the
view being updatable had odd priorities IMNSHO.)

Back-patch to v15 where archive modules were added, since that seems
to have made this more of a sore spot than it was before.

Benoit Lobréau, Nathan Bossart

Discussion: https://postgr.es/m/CAPE8EZ7KHaXMHKwT=HOim23tDVKYA1PruRuTfeYdCrYWwPGhag@mail.gmail.com

diff --git a/doc/src/sgml/system-views.sgml b/doc/src/sgml/system-views.sgml
index 44aa70a0316e7843713eed6132e1a6270cb07bae..3f573a4f0897a66178424fabf0189ab0243f4d69 100644 (file)
--- a/doc/src/sgml/system-views.sgml
+++ b/doc/src/sgml/system-views.sgml
@@ -3273,11 +3273,6 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
    ways to change these parameters.
   
 
-  
-   This view does not display customized options
-   until the extension module that defines them has been loaded.
-  
-
   
    This view cannot be inserted into or deleted from, but it can be updated.  An
    UPDATE applied to a row of pg_settings
@@ -3291,6 +3286,21 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
    SET.
   
 
+  
+   This view does not
+   display customized options
+   unless the extension module that defines them has been loaded by the
+   backend process executing the query (e.g., via a mention in
+   ,
+   a call to a C function in the extension, or the
+   LOAD command).
+   For example, since archive modules
+   are normally loaded only by the archiver process not regular sessions,
+   this view will not display any customized options defined by such modules
+   unless special action is taken to load them into the backend process
+   executing the query.
+  
+