Re: Parsing config files in a directory

Josh Berkus <josh(at)agliodbs(dot)com> writes:
> Kevin,
>> Perhaps the ease of writing something like that with sed or perl has
>> caused me to underestimate the effort required in C. I am curious
>> whether you actually mean that, or said it for rhetorical effect.

> I actually mean that. It *looks* easy in perl, and in fact *is* easy
> for *your* postgresql.conf which you control. But writing a parser for
> every postgresql.conf which exists in the world, no matter how someone
> has hacked it up creatively? No matter how they've handled upgrades?

The issue isn't even with writing a parser. The conf file is certainly
machine-parsable; guc-file.l is an existence proof, and the relatively
slow rate of change of that file indicates that it's been a reasonably
stable format over time. The issue is that if you want to modify the
file while preserving comments, commenting out superseded entries,
putting new entries where the user would expect to find them, etc etc,
you have a hard AI problem in front of you. This is why Robert keeps
harping on the default commentary being a problem --- if you removed all
comments (and didn't care about ordering etc), it would be easier.
But short of telling people who prefer $EDITOR to get lost, that's not
going to work.

I think the point of the discussions here is that we want to establish
an alternate config file (or set of config files) in which the
expectations are different: no promise to preserve any comments, no
intention to be human-friendly for editing, etc. In one sense this
would be the same machine-readable format, since the backend is still
going to parse it with guc-file.l; but changing the human expectations
can make the editing problem much simpler.

regards, tom lane