docs: Clarify that NULL arg to set_config() means reset to default

Author: David G. Johnston 
Reviewed-by: Zhang Mingli 
Discussion: https://www.postgresql.org/message-id/CAKFQuwY0SK6JdCci1VJX6xsztRXgGeVEY-grkENZx%[email protected]

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 9f531e23283e82acf46de5a2d72887dfb7f9bbbd..0224f93733dc60ebc91ad27499bb98c4f472af88 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -28576,6 +28576,11 @@ acl      | {postgres=arwdDxtm/postgres,foo=r/postgres}
         use false instead. This function corresponds to
         the SQL command .
        
+       
+        set_config accepts the NULL value for
+        new_value, but as settings cannot be null, it
+        is interpreted as a request to reset the setting to its default value.
+       
        
         set_config('log_statement_stats', 'off', false)
         off