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

On Wednesday, November 14, 2012 12:24 AM Robert Haas wrote:
On Mon, Nov 12, 2012 at 10:59 PM, Amit kapila <amit(dot)kapila(at)huawei(dot)com> wrote:

> Uh, no, I don't think that's a good idea. IMHO, what we should do is:

> 1. Read postgresql.conf.auto and remember all the settings we saw. If we see something funky like an include directive, barf.
> 2. Forget the value we remembered for the particular setting being changed. Instead, remember the user-supplied new value for that parameter.
> 3. Write a new postgresql.conf.auto based on the information remembered in steps 1 and 2.

Attached patch contains implementaion for above concept.
It can be changed to adapt the write file based on GUC variables as described by me yesterday or in some other better way.

Currenty to remember and forget, I have used below concept:
1. Read postgresql.auto.conf in memory.
2. parse the GUC_file for exact loction of changed variable
3. update the changed variable in memory at location found in step-2
4. Write the postgresql.auto.conf

Overall changes:
1. include dir in postgresql.conf at time of initdb
2. new built-in function pg_change_conf to change configuration settings
3. write file as per logic described above.

Some more things left are:
1. Transactional capability to command, so that rename of .lock file to .auto.conf can be done at commit time.

I am planing to upload the attached for this CF.

Suggestions/Comments?

With Regards,
Amit Kapila.