guc

I was playing around with adding a couple new SET commands (REAL_FORMAT
and DOUBLE_PRECISION_FORMAT as per todo list item) and I ended up
playing with GUC a bit.

I've cleaned it up a bit - most of the changes should be fairly
self-explanitory from the patch. Some of the configuration options
handled in variable.c (so far, server_encoding and seed) have been moved
into guc.c and are handled by GUC. Moving them in required adding a
couple of fields to config_generic and friends - a read_only field and a
display_proc field (hook for custom SHOW messages). I've removed
GetConfigOption() and replaced it with ShowConfigOption() which does an
elog(NOTICE) instead of returning a string.

When setting REAL_FORMAT and DOUBLE_PRECISION_FORMAT, the printf-style
format string should be checked for certain things:

  - field width of "*" is not allowed
  - precision of ".*" is not allowed
  - all conversion specifiers except "s" and "n" are allowed
  - only one conversion specification other than %% and variations is
    allowed

Does this seem reasonable to people? I haven't written a function to
check those yet.. will do soon.

This patch isn't complete yet so don't append it to the pending patches
list, Bruce.

Liam

--
Liam Stewart :: Red Hat Canada, Ltd. :: liams@redhat.com