On Tues, Apr 4, 2023 at 23:48 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Nathan Bossart <nathandboss...@gmail.com> writes: > > On Wed, Feb 22, 2023 at 12:40:07PM +0000, wangw.f...@fujitsu.com wrote: > >> After some rethinking, I think users can easily get exact value according > >> to > >> exact formula, and I think using accurate formula can help users adjust > >> max_locks_per_transaction or max_predicate_locks_per_transaction if > needed. So, > >> I used the exact formulas in the attached v2 patch. > > > IMHO this is too verbose. > > Yeah, it's impossibly verbose. Even the current wording does not fit > nicely in pg_settings output. > > > Perhaps it could be simplified to something like > > The shared lock table is sized on the assumption that at most > > max_locks_per_transaction objects per eligible process or prepared > > transaction will need to be locked at any one time. > > I like the "per eligible process" wording, at least for guc_tables.c; > or maybe it could be "per server process"? That would be more > accurate and not much longer than what we have now. > > I've got mixed emotions about trying to put the exact formulas into > the SGML docs either. Space isn't such a constraint there, but I > think the info would soon go out of date (indeed, I think the existing > wording was once exactly accurate), and I'm not sure it's worth trying > to maintain it precisely.
Thanks both for sharing your opinions. I agree that verbose descriptions make maintenance difficult. For consistency, I unified the formulas in guc_tables.c and pg-doc into the same suggested short formula. Attach the new patch. > One reason that I'm not very excited about this is that in fact the > formula seen in the source code is not exact either; it's a lower > bound for how much space will be available. That's because we throw > in 100K slop at the bottom of the shmem sizing calculation, and a > large chunk of that remains available to be eaten by the lock table > if necessary. Thanks for sharing this. Since no one has reported related issues, I'm also fine to close this entry if this related modification is not necessary. Regards, Wang Wei
v3-0001-Fix-the-description-of-shared-lock-table-size-and.patch
Description: v3-0001-Fix-the-description-of-shared-lock-table-size-and.patch
