On Wed, Oct 2, 2024 at 10:02 AM Masahiko Sawada <sawada.m...@gmail.com> wrote: > > On Tue, Oct 1, 2024 at 8:57 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > > > > Noah Misch <n...@leadboat.com> writes: > > > On Tue, Oct 01, 2024 at 11:55:48AM -0700, Masahiko Sawada wrote: > > >> Considering that the population of database cluster signedness will > > >> converge to signedness=true in the future, we can consider using > > >> -fsigned-char to prevent similar problems for the future. We need to > > >> think about possible side-effects as well, though. > > > > > It's good to think about -fsigned-char. While I find it tempting, several > > > things would need to hold for us to benefit from it: > > > > > - Every supported compiler has to offer it or an equivalent. > > > - The non-compiler parts of every supported C implementation need to > > > cooperate. For example, CHAR_MIN must change in response to the flag. > > > See > > > the first comment in cash_in(). > > > - Libraries we depend on can't do anything incompatible with it. > > > > > Given that, I would lean toward not using -fsigned-char. It's unlikely > > > all > > > three things will hold. Even if they do, the benefit is not large. > > > > I am very, very strongly against deciding that Postgres will only > > support one setting of char signedness. It's a step on the way to > > hardware monoculture, and we know where that eventually leads. > > (In other words, I categorically reject Sawada-san's assertion > > that signed chars will become universal. I'd reject the opposite > > assertion as well.) > > Thank you for pointing this out. I agree with both of you. >
I've attached PoC patches for the idea Noah proposed. Newly created clusters unconditionally have default_char_signedness=true, and the only source of signedness=false is pg_upgrade. To update the signedness in the controlfile, pg_resetwal now has a new option --char-signedness, which is used by pg_upgrade internally. Feedback is very welcome. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com
v2-0005-Fix-an-issue-with-index-scan-using-pg_trgm-due-to.patch
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v2-0004-pg_upgrade-Add-set-char-signedness-to-set-the-def.patch
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v2-0001-Add-default_char_signedness-field-to-ControlFileD.patch
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v2-0003-pg_upgrade-Inherit-default-char-signedness-from-o.patch
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v2-0002-pg_resetwal-Add-char-signedness-option-to-change-.patch
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