From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Teodor Sigaev <teodor(at)sigaev(dot)ru>, Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: knngist - 0.8 |
Date: | 2010-11-23 16:25:34 |
Message-ID: | AANLkTi=WhcD3t8iQUd+T3uQnEHbNe5HuyuQo2k=mxU59@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, Nov 23, 2010 at 11:12 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Mon, Nov 22, 2010 at 11:05 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> I'm satisfied to say that only one sort order can be associated with a
>>> particular operator in a particular opclass, which is what would be
>>> implied by using AMOP_SEARCH/AMOP_ORDER as the unique key component.
>
>> Does that imply that KNNGIST would only be able to support one
>> ordering per AMOP_ORDER-operator, or does it imply that each such
>> ordering would require a separate strategy number? The second might
>> be OK, but the first sounds bad.
>
> It would be the first, because simply assigning another strategy number
> only satisfies one of the unique constraints on pg_amop. To allow
> arbitrary flexibility here, we would have to include all components of
> the ordering specification in the unique constraint that's presently
> just (amopopr, amopfamily) and is proposed to become
> (amopopr, amopfamily, amoppurpose). I think that's an undue amount of
> complexity to support something that's most likely physically impossible
> from the index's standpoint anyway.
Or, you'd need to pass these details separately to the AM, which seems
like a more more flexible way of doing it.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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