From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
Cc: | Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>, Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> |
Subject: | Re: knngist - 0.8 |
Date: | 2010-12-28 16:12:40 |
Message-ID: | 3247.1293552760@sss.pgh.pa.us |
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Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> On Sun, Dec 26, 2010 at 08:13:40PM -0500, Tom Lane wrote:
>> [ thinks for a bit... ] One reason for having a different structure
>> would be if we needed to represent abstract semantics for some operators
>> that couldn't be associated with a btree opclass.
> One thing that comes to mind is the operators used for hash indexes,
> namely the hash() function.
The hash opclasses handle that fine. I cannot conceive of any reason
for shoehorning hash functions into btree opclasses.
> With respect to the collation of strings I have thought it useful to be
> able to define a sortkey() function, which would map the input space to
> a 8 byte integer and satisfies the rule:
> sortkey(a) < sortkey(b) implies a < b
I'm pretty dubious about the workability of that one, but again, there
isn't any obvious reason why we'd need a new catalog structure to
support it. If we did want it, it could be an optional support function
in btree opclasses.
regards, tom lane
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