Re: [GENERAL] Is float8 a reference type?

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От Tom Lane
Тема Re: [GENERAL] Is float8 a reference type?
Дата
Msg-id 27465.1506184824@sss.pgh.pa.us
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Ответ на Re: [GENERAL] Is float8 a reference type?  (Paul A Jungwirth <pj@illuminatedcomputing.com>)
Ответы Re: [GENERAL] Is float8 a reference type?  (Paul A Jungwirth <pj@illuminatedcomputing.com>)
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Paul A Jungwirth <pj@illuminatedcomputing.com> writes:
> Since I'm expecting ~10 million elements per array, it seems like
> skipping the conversion will have a real effect. I checked the
> assembly and do see a difference (on both Mac+clang and Linux+gcc).

I wonder whether you're using up-to-date Postgres headers (ones
where Float8GetDatum is a static inline function).  For me, both
of those platforms recognize it as a no-op --- in fact, clang
turns a loop like
   for (i = 0; i < n; i++) {       datums[i] = Float8GetDatum(floats[i]);   }

into something that looks suspiciously like an inlined, loop-unrolled
memcpy().
        regards, tom lane


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