Thread: Re: [BUGS] pg_service.conf ignores dbname parameter
Michael Fuhr <mfuhr@fuhr.org> writes:
> When a client connects to the database server using a service name,
> the dbname parameter in pg_service.conf is ignored. In the absence
> of an explicitly-named database in the connection string, the service
> name is used as the database name regardless of that service's
> dbname setting.
> [snip]
> I haven't yet examined the rest of the code closely enough to come
> up with the correct patch, but it seems that the "set the database
> name to the name of the service" code should be deferred until
> after all of the service's parameters have been read.
Hm. I'm of the opinion that the real problem here is the code's
assumption that it is reasonable to force dbname = servicename when
the service file doesn't say any such thing. For all other parameters,
omitting the parameter from pg_service.conf causes the standard default
to be adopted. Why should dbname work differently? It saves only a
minimal amount of typing to do it this way, and it might prevent some
useful setups (namely, a service that specifies connection params but
allows the usual default of dbname = username to apply).
Since pg_service was completely undocumented before 7.4, I think it is
safe to say that its usage in the field is nil except for the original
author, and therefore "backwards compatibility" is not really a relevant
argument just yet. We ought to concentrate on "principle of least
astonishment" instead.
Accordingly, I'd rather just delete the offending code instead of move
it. (BTW, I notice Bruce has fooled with this code before, so it's
already in the "known source of problems" category.)
Comments anyone?
regards, tom lane
Tom Lane wrote: > Michael Fuhr <mfuhr@fuhr.org> writes: > > When a client connects to the database server using a service name, > > the dbname parameter in pg_service.conf is ignored. In the absence > > of an explicitly-named database in the connection string, the service > > name is used as the database name regardless of that service's > > dbname setting. > > [snip] > > I haven't yet examined the rest of the code closely enough to come > > up with the correct patch, but it seems that the "set the database > > name to the name of the service" code should be deferred until > > after all of the service's parameters have been read. > > Hm. I'm of the opinion that the real problem here is the code's > assumption that it is reasonable to force dbname = servicename when > the service file doesn't say any such thing. For all other parameters, > omitting the parameter from pg_service.conf causes the standard default > to be adopted. Why should dbname work differently? It saves only a > minimal amount of typing to do it this way, and it might prevent some > useful setups (namely, a service that specifies connection params but > allows the usual default of dbname = username to apply). > > Since pg_service was completely undocumented before 7.4, I think it is > safe to say that its usage in the field is nil except for the original > author, and therefore "backwards compatibility" is not really a relevant > argument just yet. We ought to concentrate on "principle of least > astonishment" instead. > > Accordingly, I'd rather just delete the offending code instead of move > it. (BTW, I notice Bruce has fooled with this code before, so it's > already in the "known source of problems" category.) Agreed. Just make them supply the dbname in the service file. I can make the changes and update the documentation in pg_service.conf: # included in this file. If no database name is specified, it is assumed # to match the service name. Lines beginning with '#' are comments. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania19073
Tom Lane wrote: > Hm. I'm of the opinion that the real problem here is the code's > assumption that it is reasonable to force dbname = servicename when > the service file doesn't say any such thing. For all other > parameters, omitting the parameter from pg_service.conf causes the > standard default to be adopted. Why should dbname work differently? Regardless of this particular issue, I think it would be useful if, under some conditions to be identified, some service were taken as default if nothing is specied in libpq. That would eliminate the need to set environment variables, which is undesirable in many situations.
Peter Eisentraut <peter_e@gmx.net> writes:
> Regardless of this particular issue, I think it would be useful if,
> under some conditions to be identified, some service were taken as
> default if nothing is specied in libpq. That would eliminate the need
> to set environment variables, which is undesirable in many situations.
That's a thought. Maybe if pg_service.conf exists and contains a
section named "default", we use whatever settings are present there?
(Obviously we'd not want the dbname to be forced by this, but I think
we've already agreed to get rid of that behavior.)
About the only downside I can see to this is that every connection
would incur the overhead of an attempted file opening. That might be
thought to be too much overhead, at least by people who have no use
for the feature. But in comparison to what will happen on the server
side during backend startup, it's probably pretty negligible.
BTW, why is it that pg_service.conf is system-wide? Personally I'd
think it more useful to seek settings in ~/.pg_service.conf.
regards, tom lane
Tom Lane wrote: > Peter Eisentraut <peter_e@gmx.net> writes: > > Regardless of this particular issue, I think it would be useful if, > > under some conditions to be identified, some service were taken as > > default if nothing is specied in libpq. That would eliminate the need > > to set environment variables, which is undesirable in many situations. > > That's a thought. Maybe if pg_service.conf exists and contains a > section named "default", we use whatever settings are present there? > (Obviously we'd not want the dbname to be forced by this, but I think > we've already agreed to get rid of that behavior.) > > About the only downside I can see to this is that every connection > would incur the overhead of an attempted file opening. That might be > thought to be too much overhead, at least by people who have no use > for the feature. But in comparison to what will happen on the server > side during backend startup, it's probably pretty negligible. > > BTW, why is it that pg_service.conf is system-wide? Personally I'd > think it more useful to seek settings in ~/.pg_service.conf. Perhaps the solution is to allow an environment variable to point to the services file. That way, you only look for the file if that variable exists. This would also have to be defined for any service file usage, so maybe this is bad. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania19073
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Tom Lane wrote:
>> BTW, why is it that pg_service.conf is system-wide? Personally I'd
>> think it more useful to seek settings in ~/.pg_service.conf.
> Perhaps the solution is to allow an environment variable to point to the
> services file.
Peter was after a no-environment-variable solution, so I don't think
he'll like that one.
regards, tom lane
Tom Lane wrote: > Bruce Momjian <pgman@candle.pha.pa.us> writes: > > Tom Lane wrote: > >> BTW, why is it that pg_service.conf is system-wide? Personally I'd > >> think it more useful to seek settings in ~/.pg_service.conf. > > > Perhaps the solution is to allow an environment variable to point to the > > services file. > > Peter was after a no-environment-variable solution, so I don't think > he'll like that one. I thought he was more concerned about removing envirnment variables that have to be tuned for each user. Let's see how he responds. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania19073
Bruce Momjian wrote: > I thought he was more concerned about removing envirnment variables > that have to be tuned for each user. Let's see how he responds. Think about a web server talking to a database server. Where do you set the environment variables for that? Or where is the "home directory" for that? And then remember issues of "su" vs. "su -". Environment variables are error prone when they contain information that is essential for running the program correctly.