ALTER SYSTEM and GUC_LIST_QUOTE

All,

While testing some behaviors with ALTER SYSTEM I discovered that GUC
parameters with the GUC_LIST_QUOTE flag have a potential issue.

As an example,

ALTER SYSTEM SET shared_preload_libraries = '';

Results in the following output in postgresql.auto.conf:

shared_preload_libraries = '""';

Therefore, when attempting to restart postgres the following error is
encountered:

FATAL:  could not access file "": No such file or directory

As well, specifying multiple items:

ALTER SYSTEM SET shared_preload_libraries = 'foo,bar';

Results in:

shared_preload_libraries = '"foo,bar"';

Which doesn't parse out into separate list items and therefore obviously fails.

I think from an ALTER SYSTEM perspective this is an issue, as I would
expect to be able to set these types of parameters to any valid value,
including an empty list.  I'm willing to accept that there might be
something here that I am missing or not understanding about how this
should work, but this doesn't seem right.

Thoughts?

-Adam

-- 
Adam Brightwell - adam.brightwell@crunchydatasolutions.com
Database Engineer - www.crunchydatasolutions.com