| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: File-per-GUC WAS: Re: ALTER SYSTEM SET command to change postgresql.conf parameters (RE: Proposal for Allow postgresql.conf values to be changed via SQL [review]) |
| Date: | 2013-08-05 17:56:40 |
| Message-ID: | 32192.1375725400@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Josh Berkus <josh(at)agliodbs(dot)com> writes:
> I'll also point out that some of our settings only really "work" in
> combinations of two or more settings. For example, one doesn't want to
> set archive_mode = on unless one is setting archive_command as well.
> And generally if one sets sequential_page_cost, one is changing the
> other cost parameters as well. And logging parameters are generally
> managed as a set.
> So the case of two sessions both modifying ALTER SYSTEM SET, and one
> succeeding for some-but-all-GUCS, and the other succeeding for
> some-but-not-all-GUCs, would not be user-friendly or pretty, even if
> each setting change succeeded or failed atomically.
That is a killer point. So really the value of the global lock is to
ensure serializability when transactions are updating multiple GUCs.
regards, tom lane