Re: Permanent settings

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On Wed, 20 Feb 2008 09:42:02 -0500
Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:

> All this discussion seems to me to be going off into the clouds,
> where every objection is met with some still more elaborate scheme. I
> think we need to look at simple, incremental, and if possible
> backwards compatible changes.

The simplest solution I can think of is:

Have a table pg_configuration (pg_settings?).

Allow that table to be inserted into but not updated or deleted from.

Provide functions to manipulate the table perhaps:

select update_settings('shared_memory','64M');

That table is used as the definitive source for "building" the
postgresql.conf.

The postgresql.conf is pushed to disk each time the system is reloaded
via:

refresh_settings();

Refresh_settings would be called as an initial startup function as
well. So if you did:

pg_ctl -D data start

It would actually do:

pg_ctl -D data start; select update_settings(); pg_ctl -D data
restart;

The reason we only insert is that the function refresh_settings() calls
the max(created) for the setting. That way we can know what previous
settings for the GUC.

Other things could be added such as:

select update_settings('shared_memory','64M','Used to be 16 but we
got more ram');

The one thing this does is make the postgresql.conf basically a
placeholder. It is not definitive anymore, in the sense that settings
will be overwritten on restart. That really isn't that uncommon anyway
in other applications.

Sincerely,

Joshua D. Drake

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