| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, "Bossart, Nathan" <bossartn(at)amazon(dot)com>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "wangsh(dot)fnst(at)fujitsu(dot)com" <wangsh(dot)fnst(at)fujitsu(dot)com>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Greg Sabino Mullane <htamfids(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: make MaxBackends available in _PG_init |
| Date: | 2022-04-12 20:58:42 |
| Message-ID: | 918045.1649797122@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Nathan Bossart <nathandbossart(at)gmail(dot)com> writes:
> I think it'd be reasonable to allow changing custom GUCs in _PG_init().
> Those aren't going to impact things like MaxBackends.
It's reasonable to allow changing *most* GUCs in _PG_init(); let us
please not break cases that work fine today.
It seems after a bit of reflection that what we ought to do is identify
the subset of PGC_POSTMASTER GUCs that feed into shared memory sizing,
mark those with a new GUC flag, and not allow them to be changed after
shared memory is set up. (An alternative to a new flag bit is to
subdivide the PGC_POSTMASTER context into two values, but that seems
like it'd be far more invasive. A flag bit needn't be user-visible.)
Then, what we'd need to do is arrange for shared-preload modules to
receive their _PG_init call before shared memory creation (when they
can still twiddle such GUCs) and then another callback later.
regards, tom lane
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