Fix GUC_NO_SHOW_ALL test scenario in 003_check_guc.pl

Hi,

The commit 7265dbffad7feac6ea9d373828583b5d3d152e07 has added a script
in src/backend/utils/misc/check_guc that cross-checks the consistency
of the GUCs with postgresql.conf.sample, making sure that its format
is in line with what guc.c has. As per the commit message, the
parameters which are not listed as NOT_IN_SAMPLE in guc.c should be
present in postgresql.conf.sample. But I have observed a test case
failure when the parameters which are listed as GUC_NO_SHOW_ALL in
guc.c and if it is present in postgresql.conf.sample. I feel this
behaviour is not expected and this should be fixed. I spent some time
on the analysis and found that query [1] is used to fetch all the
parameters which are not listed as NOT_IN_SAMPLE. But the pg_settings
view does not return the parameters listed as GUC_NO_SHOW_ALL. Hence
these records will be missed. Please share your thoughts. I would like
to work on the patch if a fix is required.

[1]:
SELECT name FROM pg_settings WHERE NOT 'NOT_IN_SAMPLE' = ANY
(pg_settings_get_flags(name)) AND name <> 'config_file' ORDER BY 1;

Thanks & Regards,
Nitin Jadhav