Re: Forgive trailing semicolons inside of config files

On Tue, 11 Jul 2023 at 10:43, Greg Sabino Mullane <htamfids(at)gmail(dot)com>
wrote:

> This has been a long-standing annoyance of mine. Who hasn't done something
> like this?:
>
> psql> SET random_page_cost = 2.5;
> (do some stuff, realize that rpc was too high)
>
> Let's put that inside of postgresql.conf:
>
>
> #------------------------------------------------------------------------------
> # CUSTOMIZED OPTIONS
>
> #------------------------------------------------------------------------------
>
> # Add settings for extensions here
>
> random_page_cost = 2.5;
>
>
> Boom! Server will not start. Surely, we can be a little more liberal in
> what we accept? Attached patch allows a single trailing semicolon to be
> silently discarded. As this parsing happens before the logging collector
> starts up, the error about the semicolon is often buried somewhere in a
> separate logfile or journald - so let's just allow postgres to start up
> since there is no ambiguity about what random_page_cost (or any other GUC)
> is meant to be set to.
>

Please, no!

There is no end to accepting sloppy syntax. What next, allow "SET
random_page_cost = 2.5;" (with or without semicolon) in config files?

I'd be more interested in improvements in visibility of errors. For
example, maybe if I try to start the server and there is a config file
problem, I could somehow get a straightforward error message right in the
terminal window complaining about the line of the configuration which is
wrong.

Or maybe there could be a "check configuration" subcommand which checks the
configuration. If it's fine, say so and set a flag saying the server is
clear to be started/restarted. If not, give useful error messages and don't
set the flag. Then make the start/restart commands only do their thing if
the "config OK" flag is set. Make sure that editing the configuration
clears the flag (or have 2 copies of the configuration, copied over by the
"check" subcommand: one for editing, one for running with).

This might properly belong outside of Postgres itself, I don't know. But I
think it would be way more useful than a potentially never-ending series of
patches to liberalize the config parser.