| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andy Fan <zhihuifan1213(at)163(dot)com>, pgsql-hackers(at)postgresql(dot)org, Noah Misch <noah(at)leadboat(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Subject: | Re: GetRelationPath() vs critical sections |
| Date: | 2025-02-21 05:35:34 |
| Message-ID: | CA+hUKGJUB9M9XS+TMzB5oaFpCC+E0m1v8Gf5BN+M7k5E8zZ0PQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Feb 21, 2025 at 6:20 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> #define PROCNUMBER_BITS 18
> #define MAX_BACKENDS ((1 << PROCNUMBER_BITS) - 1)
> #define PROCNUMBER_CHARS DECIMAL_DIGITS_FOR_BITS(PROCNUMBER_BITS)
>
> ... with a little helper ported to preprocessor hell from Hacker's
> Delight magic[1] for that last bit. See attached. But if that's a
> bit too nuts...
Erm, wait of course you just need:
#define DECIMAL_DIGITS(n) \
((n) < 10 ? 1 : \
(n) < 100 ? 2 : \
(n) < 1000 ? 3 : \
(n) < 10000 ? 4 : \
(n) < 100000 ? 5 : \
(n) < 1000000 ? 6 : \
(n) < 10000000 ? 7 : \
(n) < 100000000 ? 8 : \
(n) < 1000000000 ? 9 : 10)
#define PROCNUMBER_BITS 18
#define MAX_BACKENDS ((1 << PROCNUMBER_BITS) - 1)
#define PROCNUMBER_CHARS DECIMAL_DIGITS(MAX_BACKENDS)
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