As discussed on several occasions previously, the new anonymous

composite type capability makes it possible to create a system view
based on a table function in a way that is hopefully palatable to
everyone. The attached patch takes advantage of this, moving
show_all_settings() from contrib/tablefunc into the backend (renamed
all_settings(). It is defined as a builtin returning type RECORD. During
initdb a system view is created to expose the same information presently
available through SHOW ALL. For example:

test=# select * from pg_settings where name like '%debug%';
          name          | setting
-----------------------+---------
  debug_assertions      | on
  debug_pretty_print    | off
  debug_print_parse     | off
  debug_print_plan      | off
  debug_print_query     | off
  debug_print_rewritten | off
  wal_debug             | 0
(7 rows)


Additionally during initdb two rules are created which make it possible
to change settings by updating the system view -- a "virtual table" as
Tom put it. Here's an example:

Joe Conway

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: builtins.h,v 1.190 2002/08/09 16:45:16 tgl Exp $
+ * $Id: builtins.h,v 1.191 2002/08/15 02:51:27 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -662,6 +662,7 @@ extern Datum quote_literal(PG_FUNCTION_ARGS);
 /* guc.c */
 extern Datum show_config_by_name(PG_FUNCTION_ARGS);
 extern Datum set_config_by_name(PG_FUNCTION_ARGS);
+extern Datum show_all_settings(PG_FUNCTION_ARGS);
 
 /* catalog/pg_conversion.c */
 extern Datum pg_convert3(PG_FUNCTION_ARGS);