Re: Re: Proposal for Allow postgresql.conf values to be changed via SQL [review]

On Tue, Jan 22, 2013 at 11:07 PM, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> On Tuesday, January 22, 2013 7:10 PM Zoltán Böszörményi wrote:
>> 2013-01-22 13:32 keltezéssel, Amit kapila írta:
>> > On Saturday, January 19, 2013 2:37 AM Boszormenyi Zoltan wrote:
>> > 2013-01-18 21:48 keltezéssel, Boszormenyi Zoltan írta:
>> >> 2013-01-18 21:32 keltezéssel, Tom Lane írta:
>> >>> Boszormenyi Zoltan <zb(at)cybertec(dot)at> writes:
>> >>>> 2013-01-18 11:05 keltezéssel, Amit kapila írta:
>> >>>>>> On using mktemp, linux compilation gives below warning
>> >>>>>> warning: the use of `mktemp' is dangerous, better use `mkstemp'
>> >
>> >>>> Everywhere else that we need to do something like this, we just
>> use our
>> >>>> own PID to disambiguate, ie
>> >>>> sprintf(tempfilename, "/path/to/file.%d", (int) getpid());
>> >>>> There is no need to deviate from that pattern or introduce
>> portability
>> >>>> issues, since we can reasonably assume that no non-Postgres
>> programs are
>> >>>> creating files in this directory.
>> >>> Thanks for the enlightenment, I will post a new version soon.
>> >> Here it is.
>> > The patch sent by you works fine.
>> > It needs small modification as below:
>> >
>> > The "auto.conf.d" directory should follow the postgresql.conf file
>> directory not the data_directory.
>> > The same is validated while parsing the postgresql.conf configuration
>> file.
>> >
>> > Patch is changed to use the postgresql.conf file directory as below.
>> >
>> > StrNCpy(ConfigFileDir, ConfigFileName, sizeof(ConfigFileDir));
>> > get_parent_directory(ConfigFileDir);
>> > /* Frame auto conf name and auto conf sample temp file name */
>> > snprintf(AutoConfFileName, sizeof(AutoConfFileName), "%s/%s/%s",
>> > ConfigFileDir,
>> > PG_AUTOCONF_DIR,
>> > PG_AUTOCONF_FILENAME);
>>
>> Maybe it's just me but I prefer to have identical
>> settings across all replicated servers. But I agree
>> that there can be use cases with different setups.
>>
>> All in all, this change makes it necessary to run the
>> same SET PERSISTENT statements on all slave servers,
>> too, to make them identical again if the configuration
>> is separated from the data directory (like on Debian
>> or Ubuntu using the default packages). This needs to be
>> documented explicitly.
>
> SET PERSISTENT command needs to run on all slave servers even if the path we
> take w.r.t data directory
> unless user takes backup after command.

Is it safe to write something in the directory other than data directory
via SQL?

postgres user usually has the write permission for the configuration
directory like /etc/postgresql?

>> > This closes all comments raised till now for this patch.
>> > Kindly let me know if you feel something is missing?
>>
>> I can't think of anything else.

For removing
+ a configuration entry from <filename>postgresql.auto.conf</filename> file,
+ use <command>RESET PERSISTENT</command>. The values will be effective
+ after reload of server configuration (SIGHUP) or server startup.

The description of RESET PERSISTENT is in the document, but it
seems not to be implemented.

Regards,

--
Fujii Masao