From: | Stephen Frost <sfrost(at)snowman(dot)net> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <bruce(at)momjian(dot)us>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, Josh Berkus <josh(at)agliodbs(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: ALTER SYSTEM SET command to change postgresql.conf parameters (RE: Proposal for Allow postgresql.conf values to be changed via SQL [review]) |
Date: | 2013-08-30 13:49:12 |
Message-ID: | 20130830134912.GH2706@tamriel.snowman.net |
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* Robert Haas (robertmhaas(at)gmail(dot)com) wrote:
> there's a fairly generous but fixed-at-startup-time limit on how many
> segments you can have. In practice I don't think this matters much,
> but it was a sobering reminder that the main shared memory segment,
> with all of its inflexibility, has important reliability properties
> that are hard to replicate in more dynamic scenarios.
Why wouldn't it be possible to have the same arrangment for
shared_buffers, where you have more entires than you 'need' at startup
but which then allows you to add more shared segments later? I do see
that we would need an additional bit of indirection to handle that,
which might be too much overhead, but the concept seems possible. Isn't
that more-or-less how the kernel handles dynamic memory..?
> Under the currently-proposed design, it can't be used to do any such
> thing. It can only be used to modify some auto.conf file which lives
> in $PGDATA. It's therefore no different from the ops perspective than
> ALTER DATABASE or ALTER USER - except that it allows all settings to
> be changed rather than only a subset.
Claiming that modifying a file *included from a file in /etc* doesn't
modify things under /etc is disingenuous, imv.
Thanks,
Stephen
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