Re: change the value of "unix_socket_directories" , must used "-h /xx/xx" to use the Unix domain socket

On Aug 16, 2014, at 9:01 AM, Nick Guenther <nguenthe(at)uwaterloo(dot)ca> wrote:

>
>
> On August 16, 2014 11:41:02 AM EDT, lin <jluwln(at)163(dot)com> wrote:
>> Hi all,
>> I change the value of "unix_socket_directories" in postgresql.conf ,
>> then restart the database, but it cannot connect the database used like
>> this
>> "psql -d postgres -p 5432" , it must given the parameter " -h /xx/xx"
>> to use the Unix domain socket。
>> how to fix this issue ?
>
> I'll start by saying that your test case is very clear, and thank you for it. I am unsure what your goal is, however. I assume you are trying to set up parallel postgres processes, for debugging. I've done this recently, for that reason.
>
> First thing to point out is that you need only one of -h and -p. They are redundant options, because you only connect to postgres either over TCP (-p) or with a unix domain socket (-h).

Not really. In the case of a TCP connection you need -h for the hostname and -p for the port. For a unix socket connection you use -h to specify the directory the unix socket is in, and -p is used to generate the name of the socket within that directory. If you omit one or both then the compiled-in defaults will be used, but it still uses both values to connect.

>
> Second, what you're seeing is necessary. If you change the default, then psql doesn't know where to look. However, you can recover the old behaviour with shell tricks:
> $ alias psql='psql -h /xx/xx'
> $ psql -d postgres

Setting environment variables to point to your preferred instance will also work - and it'll work with any client that uses libpq (which is probably almost everything that's not java).

Cheers,
Steve

>
> (Personally, I wrote a short wrapper script called "client.sh" which depth-first searches for a postgres db directory and the runs 'psql -h' with the first one it finds; equally well you could have this script install an alias)
>
> Are you perhaps confused about what a unix domain socket is? Why are you changing it? This is a decent description of it:
> http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man4/unix.4
>
>
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