| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Xiaoran Wang <fanfuxiaoran(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Andrew Kane <andrew(at)ankane(dot)org>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com> |
| Subject: | Re: Avoid computing ORDER BY junk columns unnecessarily |
| Date: | 2023-12-22 17:31:52 |
| Message-ID: | 1067708.1703266312@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
> On 22/12/2023 17:24, Tom Lane wrote:
>> How much of your patchset still makes sense if we assume that we
>> can always extract the ORDER BY column values from the index?
> That would make it much less interesting. But I don't think that's a
> good assumption. Especially in the kNN case, the ORDER BY value would
> not be stored in the index. Most likely the index needs to calculate it
> in some form, but it might take shortcuts like avoiding the sqrt().
Yeah, fair point. I'll try to take a look at your patchset after
the holidays.
regards, tom lane
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