From: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
---|---|
To: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
Cc: | David Rowley <dgrowleyml(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de> |
Subject: | Re: Speedup usages of pg_*toa() functions |
Date: | 2020-06-09 19:51:58 |
Message-ID: | CAEudQAp5o4sp=EoE-LNRneW=RcmQFfVZ0OKRP4RqMOcqJAy92w@mail.gmail.com |
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Em ter., 9 de jun. de 2020 às 15:53, Andrew Gierth <
andrew(at)tao11(dot)riddles(dot)org(dot)uk> escreveu:
> >>>>> "Ranier" == Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> writes:
>
> Ranier> Where " ends up with two copies of pg_ultoa_n inlined into it",
> Ranier> in this simplified example?
>
> The two references to sprintf are both inlined copies of your pg_utoa.
>
> Ranier> (b) I call this tail cut, I believe it saves time, for sure.
>
> You seem to have missed the point that the pg_ultoa_n / pg_ulltoa_n
> functions DO NOT ADD A TRAILING NUL. Which means that pg_ltoa / pg_lltoa
> can't just tail call them, since they must add the NUL after.
>
> Ranier> Regarding bugs:
>
> Ranier> (c) your version don't check size of a var, when pg_ulltoa_n
> Ranier> warning about "least MAXINT8LEN bytes."
>
> Ranier> So in theory, I could blow it up, by calling pg_lltoa.
>
> No. Callers of pg_lltoa are required to provide a buffer of at least
> MAXINT8LEN+1 bytes.
>
Thanks for explanations.
So I would change, just the initialization (var uvalue), even though it is
irrelevant.
int
pg_lltoa(int64 value, char *a)
{
int len = 0;
uint64 uvalue;
if (value < 0)
{
uvalue = (uint64) 0 - uvalue;
a[len++] = '-';
}
else
uvalue = value;
len += pg_ulltoa_n(uvalue, a + len);
a[len] = '\0';
return len;
}
regards,
Ranier Vilela
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