| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
| Subject: | Re: Optimizing pg_trgm makesign() (was Re: WIP: Fast GiST index build) |
| Date: | 2011-07-02 18:46:10 |
| Message-ID: | 16471.1309632370@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> Ah, that opens the door to do something I considered earlier but
> rejected because of alignment: instead of three 32-bit word fetches, we
> could fetch one 64-bit word and 32-bit word. Might shave a few more
> cycles...
Hm ... I suspect that might be a small win on natively-64-bit machines,
but almost certainly a loss on 32-bitters.
> Meanwhile, I experimented with optimizing the other part of the loop:
> the HASH() macros for setting the right bits in the signature.
Yeah, I was eyeing that too, but I'm hesitant to hard-wire assumptions
about the size of the signature.
regards, tom lane
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