| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Jeevan Ladhe <jeevan(dot)ladhe(at)enterprisedb(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Binary search in fmgr_isbuiltin() is a bottleneck. |
| Date: | 2017-09-27 18:40:20 |
| Message-ID: | 9626.1506537620@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2017-09-27 13:46:50 -0400, Tom Lane wrote:
>> The other question that ought to be answered is whether a gperf hash
>> table would be faster.
> Ugh, hacking together a quick input file for gperf, I'm *far* from
> convinced. The generated code does multiple lookups in significantly
> sized arrays, and assumes string input. The latter seems like a complete
> dealbreaker, and there doesn't seem to be an option to turn it off.
Ugh. I'd never actually used gperf, and now I know why not ;-)
However, that's just the first tool that came to mind. Wikipedia's
article on perfect hashes links to our man Jenkins:
http://burtleburtle.net/bob/hash/perfect.html
which looks pretty promising.
regards, tom lane
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