Make allow_system_table_mods settable at run time

petere · petere · commit c4a7a392ec8f · 2019-11-29T10:22:13.000+01:00
Make allow_system_table_mods settable at run time by superusers. It was previously postmaster start only. We don't want to make system catalog DDL wide-open, but there are occasionally useful things to do like setting reloptions or statistics on a busy system table, and blocking those doesn't help anyone. Also, this enables the possibility of writing a test suite for this setting. Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/8b00ea5e-28a7-88ba-e848-21528b632354%402ndquadrant.com
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
@@ -9501,9 +9501,11 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
       </term>
       <listitem>
        <para>
-        Allows modification of the structure of system tables.
-        This is used by <command>initdb</command>.
-        This parameter can only be set at server start.
+        Allows modification of the structure of system tables as well as
+        certain other risky actions on system tables.  This is otherwise not
+        allowed even for superusers.  Ill-advised use of this setting can
+        cause irretrievable data loss or seriously corrupt the database
+        system.  Only superusers can change this setting.
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
@@ -1777,7 +1777,7 @@ static struct config_bool ConfigureNamesBool[] =
 	},
 
 	{
-		{"allow_system_table_mods", PGC_POSTMASTER, DEVELOPER_OPTIONS,
+		{"allow_system_table_mods", PGC_SUSET, DEVELOPER_OPTIONS,
 			gettext_noop("Allows modifications of the structure of system tables."),
 			NULL,
 			GUC_NOT_IN_SAMPLE

Original file line number	Diff line number	Diff line change
`@@ -1777,7 +1777,7 @@ static struct config_bool ConfigureNamesBool[] =`
`1777`	`1777`	`},`
`1778`	`1778`
`1779`	`1779`	`{`
`1780`		`- {"allow_system_table_mods", PGC_POSTMASTER, DEVELOPER_OPTIONS,`
	`1780`	`+ {"allow_system_table_mods", PGC_SUSET, DEVELOPER_OPTIONS,`
`1781`	`1781`	`gettext_noop("Allows modifications of the structure of system tables."),`
`1782`	`1782`	`NULL,`
`1783`	`1783`	`GUC_NOT_IN_SAMPLE`